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About this book

This is the second volume of a two volume set which presents the results of the 31st International Symposium on Shock Waves (ISSW31), held in Nagoya, Japan in 2017. It was organized with support from the International Shock Wave Institute (ISWI), Shock Wave Research Society of Japan, School of Engineering of Nagoya University, and other societies, organizations, governments and industry. The ISSW31 focused on the following areas: Blast waves, chemical reacting flows, chemical kinetics, detonation and combustion, ignition, facilities, diagnostics, flow visualization, spectroscopy, numerical methods, shock waves in rarefied flows, shock waves in dense gases, shock waves in liquids, shock waves in solids, impact and compaction, supersonic jet, multiphase flow, plasmas, magnetohyrdrodynamics, propulsion, shock waves in internal flows, pseudo-shock wave and shock train, nozzle flow, re-entry gasdynamics, shock waves in space, Richtmyer-Meshkov instability, shock/boundary layer interaction, shock/vortex interaction, shock wave reflection/interaction, shock wave interaction with dusty media, shock wave interaction with granular media, shock wave interaction with porous media, shock wave interaction with obstacles, supersonic and hypersonic flows, sonic boom, shock wave focusing, safety against shock loading, shock waves for material processing, shock-like phenomena, and shock wave education. These proceedings contain the papers presented at the symposium and serve as a reference for the participants of the ISSW 31 and individuals interested in these fields.

Table of Contents

Frontmatter

Strength and Frequency of Underwater Shock Waves Related to Sterilization Effects on a Marine Bacterium

The paper reported on a study of sterilization effects on marine Vibrio sp. under different strength and frequencies of underwater shock waves generated by electric discharges. Bio-experiments were carried out with the induced bubbles behind the underwater shock waves in a cylindrical water chamber. Propagation behaviors of the shock wave in the water chamber are analyzed using an axisymmetric numerical simulation, and pressure measurement is also carried out. The generation of the bubbles is investigated using an optical method. As a result, the marine bacteria are completely inactivated in a short time, and it is clarified that sterilization effect is closely related with the number density of bubbles, pressure, and frequencies of underwater shock waves.

J. Wang, A. Abe, N. Ito, K. Nishibayashi

Effects of Liquid Impurity on Laser-Induced Gas Breakdown in Quiescent Gas: Experimental and Numerical Investigations

This paper reports that the presence of liquid impurity significantly affects the shock wave structure induced by laser-induced gas breakdown in a quiescent gas. A spherical blast wave is formed when there are no suspended liquid particles, whereas an elliptic shaped blast wave appears in gas breakdown with the presence of suspended liquid particles. The elliptic shaped blast wave has a higher overpressure magnitude on the perpendicular axis of the laser path.

T. Ukai, H. Zare-Behtash, C. White, K. Kontis

Air Blast from a Structural Reactive Material Solid

A reactive hot spot concept was investigated for fine fragmentation of a structural reactive material (SRM) solid under explosive loading to augment air blast through rapid reaction of fine SRM fragments. Micro-sized MoO3 particles were distributed in a particulate aluminum base in 10Al + MoO3, which was consolidated into a full-density solid. The SRM solid was made of a thick-walled cylindrical casing containing a high explosive. Intermetallic reactions of micro-sized MoO3 and nearby Al under explosive loading created heat and gas products to form microscale hot spots that initiated local fractures leading to fine fragments of the rest of Al. Experiments in a cylindrical chamber demonstrated the presence of a large amount of fine Al fragments, whose prompt reaction after detonation significantly enhanced the primary and near-field blast wave, thus verifying the concept.

F. Zhang, M. Gauthier, C. V. Cojocaru

Experimental Study on Configuration Effects of Supersonic Projectiles in Transitional Ballistic Regimes

The flow field associated with a moving projectile in the transitional ballistic regime is highly complicated and unsteady. The projectile interactions with the surrounding flow field affect the aerodynamic force acting on the projectile and have great impact on its stability, control, and dispersion characteristics. There are interesting fluid dynamic phenomena in this regime where the projectile interacts with the unsteady jet. One of the profound interactions is a situation in which the projectile overtakes the primary blast wave in the vicinity of the gun muzzle itself where the blast wave is very strong. In the present study, experiments are conducted with projectiles of cylindrical, conical, and hemispherical shapes, in order to understand the characteristics of projectile-flow field interactions and the projectile overtaking phenomenon, in particular. Flow field is captured using time-resolved schlieren flow visualization technique. The behavior of different shaped projectiles in the transitional ballistic regime is analyzed to understand the configuration effects. The various overtaking regimes are also identified by constructing the x-t diagram from the trajectory information obtained by image processing.

C. M. Athira, G. Rajesh

Non-ideal Blast Waves from Particle-Laden Explosives

When an explosive charge is surrounded by an inert granular material, the resulting blast overpressure is attenuated due to the transfer of the chemical energy released to the kinetic energy of the material and energy dissipation during compaction of the porous particle bed. In the present paper, the effect of various parameters on the blast wave attenuation and profile during explosive particle dispersal is explored with a multiphase hydrocode. The results indicate that as the particles are accelerated, the blast overpressure falls below the blast pressure for a homogeneous charge of the same mass in the near field but then recovers at a scaled distance of about 5 as the particles decelerate. Although the peak overpressure is reduced in the near field, the overall loading on a nearby structure may actually be increased when the interaction of the flow and particles with the structure are taken into account.

Q. T. Pontalier, M. G. Lhoumeau, D. L. Frost

Attenuation of Blast Wave in a Duct with Expansion Region (Effects of Configuration, Porous Panel, and Acoustic Material)

With recent increase of cars, the noise problem has been caused by exhaust sounds generated from exhaust pipes, which consist of weak pressure waves called blast waves. To diminish the noise, a silencer is installed in front of the exhaust pipe. In the present study, reflectors were installed in the high-pressure portion of the shock tube to generate blast waves, and as silencer models, three basic types of expansion regions were combined with four types of porous panels and acoustic material of glass wool. The pressure decay was investigated by transmission and reflection factors to the incident blast wave, together with pressure histories and high-speed movies by the shadowgraph method. As results, it was confirmed that the porous panel contributed to weaken the blast wave to some extent, while the acoustic material does greatly: the one-stage expansion model with a porous panel and glass wool recorded the highest decay of the peak over pressure for transmission and the two-stage expansion model with those showed the second highest. The acoustic material also contributed to decay of reflected shock waves propagating toward an upstream duct.

M. Ishiguro, Y. Takakura

Enhancement of the DDT Process with Energetic Solid Particle

In the pulse detonation engine development, it is believed that the presence of solid particles can rapidly accelerate the flame speed and facilitate a rapid transition to the detonation. In this study, numerical simulations are performed to investigate the dynamics of the deflagration-to-detonation transition (DDT) in the pulse detonation engines using aluminium particles. The DDT process and detonation wave propagation towards the unburnt hydrogen/air mixture containing aluminium particles are numerically studied using the Eulerian-Lagrangian approaches. The numerical results show that the aluminium particles not only shorten the DDT length but also reduced the DDT time. The improvement of the DDT process is primarily attributed to the heat released from the aluminium particle surface chemical reactions. The temperature associated with the DDT process is higher than the case of no energetic particle added, with an accompanying rise in the pressure. The more aluminium particles are added, the more heat is released in the combustion process, thereby, resulting in a faster DDT process. In essence, energetic particles contribute to the DDT process of successfully transiting to detonation waves for the (failure) cases, in which the fuel mixture can be either too lean or too rich.

Van Bo Nguyen, Quoc Thien Phan, Jiun-Ming Li, Boo Cheong Khoo, Chiang Juay Teo

Large-Scale Computation of Direct Initiation of Cylindrical Detonations

We investigate the direct initiation of cylindrical detonations in free space by performing large-scale computations on a supercomputer. The two-dimensional (2D) compressible reactive Euler equations with a one-step chemical reaction model are solved by a well-validated upwind CE/SE scheme using up to 1.6 billion mesh points. Numerical results imply that one-dimensional (1D) approaches can only interpret the direct initiation mechanism of stable detonations. Inherent multi-dimensional instabilities have a significant influence on the direct initiation of unstable detonations. On one hand, multi-dimensional instabilities make the detonation more unstable and increase the risk of failure of the detonation. On the other hand, the collision of transverse waves generated from multi-dimensional instabilities leads to the initiation of local overdriven detonations that can enhance the overall self-sustainability of the global process. The competition between these two effects is an important mechanism to interpret the direct initiation of multi-dimensional detonations.

H. Shen, M. Parsani

Numerical Study on a Cycle of Liquid Pulse Detonation Engines

A typical cycle of a liquid pulse detonation engine (PDE) often involves three main processes, which are injection and evaporation process, deflagration-to-detonation transition process (DDT), and detonation propagation process. These three processes often include a number of complex subprocesses, which strongly influence the performance characteristics of the engine. Thus, it is important to understand the physical and chemical insights of these processes in an operating cycle of the liquid PDE to improve the engine performance characteristics. In this study, numerical simulations are performed to simulate for the complete operating cycle of the liquid PDE. The numerical method is developed based on the Eulerian–Lagrangian approaches. Particularly, the continuous vapour phase is described using Navier–Stokes equations in the Eulerian frame of reference, while the liquid fuel droplets are modelled using discrete phase model in the Lagrangian frame of reference. The liquid fuel is injected into the detonation chamber through a cone nozzle injector model. The evaporation process of the liquid droplet is modelled using the D-square law. The density-based solver with a shock-capturing scheme is employed to simulate for both the DDT and detonation propagation processes. The combustion process is modelled through the reduced chemical kinetic model of Jet-A fuel. The obtained numerical results are in good agreement with both the experimental and numerical data. Both physical and chemical insights of the operating cycle are investigated. The obtained results show that the evaporation process and mixing process play a key role in the homogeneity of the fuel/air vapour mixture. The deflagration wave can successfully transit to detonation wave for a certain range of injected fuel mass flow rate. The DDT length strongly depends on the temperature of incoming airflow as well as liquid fuel mass flow rate.

Van Bo Nguyen, Quoc Thien Phan, Jiun-Ming Li, Boo Cheong Khoo, Chiang Juay Teo

Experimental Investigation on the Flame-Shock Wave Interactions in a Confined Combustion Chamber

An experiment was carried out to investigate the development and interactions of the flame and shock wave in a newly designed constant volume combustion bomb (CVCB). In this work, a stoichiometric hydrogen-air mixture was used as test fuel. An orifice plate was mounted in the middle of the CVCB to obtain flame acceleration and promote turbulent flame formation. The evolutions of flame and shock wave were captured by the high-speed schlieren photography. The flame propagation was divided into four stages: (1) laminar flame, (2) jet flame, (3) turbulent flame and (4) flame-shock wave interactions. And the development of the shock wave was observed detailedly. In addition, the effects of the initial pressure on the flame and shock wave were studied. The results show that the flame propagation velocity increased with the increase of initial pressure. The propagation velocity of the forward shock wave showed no obvious differences at different initial pressures, but the reflected shock wave from the end wall decayed faster at a higher initial pressure.

Jianfu Zhao, Lei Zhou, Haiqiao Wei, Dongzhi Gao, Zailong Xu

The Influence of Spatial Heterogeneity in Energetic Material on Non-ideal Detonation Propagation

A series of different explosive media, homogeneous or heterogeneous, was selected to examine the influences on detonation propagation in two-dimensional explosive slab bounded by a layer of inert gas with the same thermodynamic properties as reactive media. The explosive system studied is an ideal gas with a single exothermic reaction governed by a pressure-dependent reaction rate (p k) with a pressure exponent of k = 3. The heterogeneity of explosive media is imposed via a series of sinusoidal ripples in density with different wavelengths while maintaining constant pressure. The numerical simulations are initialized with a ZND solution for the ideal CJ detonation, and the detonation is allowed to propagate into the explosive layer. The results showed that the detonation in the heterogeneous medium exhibits a three-wave structure of complex shock interactions. The detonation is able to propagate into a significantly thinner layer of explosive and can exhibit a greater velocity than the corresponding homogeneous case. Also, the detonation velocity is higher during propagating in the more heterogeneous explosive medium, and the critical thickness of explosive layer that detonation can successfully propagate is also thinner in the more heterogeneous explosive medium.

Hongbin Li, Jiangling Li, Lei Zhao, Cha Xiong, Xiaocheng Mi, Andrew J. Higgins

Experimental Research on the Detonation in Gaseous Mixtures with Suspended Aluminum Particles

The experiments have been performed in a horizontal detonation tube having a 13-m-long test section with 224 mm internal diameter. The suspended aluminum particles are spherical with a diameter range of 1–50 μm, using a particle concentration of 300 g/m3 approximately. It is found that the single-front and double-front detonation waves can propagate in a mixture of φ = 1.0 H2–air and aluminum particles which react with water vapor produced by gaseous detonation. The pressure records show that the detonation structure is double front when using 50 or 30 μm aluminum particles and that single front when using 20, 10, or 1 μm ones. However, these single-front detonation waves don’t have the same properties. The detonation velocity using 1 μm particles is increased by 3.3% from the value of the baseline gas detonation as the heat release between particles and gases starts before the sonic surface and supports the shock, while the 10 and 20 μm ones start behind the sonic surface, so the detonation velocities cannot be increased. The single-front structure displayed in pressure records using 10 and 20 μm particles is because of the delay of the second front which is too short to distinguish in the pressure records.

X. Zhang, H. Chen, J. Li, S. Zhang, H. Yu

Large Eddy Simulation of Mixing Characteristic in the Cold Rotating Detonation Chamber

Two-dimensional large eddy simulation (LES) for supersonic compressible multicomponent flow is carried out to investigate the mixing characteristic of the cold non-premixed RDE with different injection strategies. According to the instantaneous and quasi-stead time-averaged flow field, the nonuniform mixing characteristic is presented. The turbulence eddy structure generated by the K-H instability is the main mechanism for promoting the mixing of fuel and oxidizer. Combining the rich and lean combustion limits, the area of the detonation is identified. It is found that the area of the detonation is only a narrow layer near the head end. To improve the mixing efficiency near the head end in the non-premixed RDE, the oxygen injection position and hydrogen injection angle are adjusted preliminary. The mixing characteristics and the area of the detonation are analyzed in detail. The present research can provide the important reference and guidance for the experimental injection design of the RDE.

R. Zhou, B. L. Tian, X. P. Li, J. P. Wang

Research on the Continuous Rotating Detonation Wave in a Hollow Chamber with Laval Nozzle

In the present study, H2/air CRD is achieved in a hollow chamber with Laval nozzle both experimentally and numerically. Three rotating patterns are obtained, which are one-wave, two dominant peak one-wave (TDPO), and two-wave modes, and the flow-field structure and effect of the nozzle contraction ratio are detailed. Both the propagation frequency and detonation wave number increase with the increase of equivalence ratio (ER) or nozzle contraction ratio. Shock wave reflection occurs at the nozzle converging section, and its upstream reflected shock wave will interact with the fresh mixture zone and inlet, leading to different rotating patterns and propagation characteristics.

Shijie Liu, Hailong Zhang, Weidong Liu

Experimental Research on a Long-Duration Operation of a Rotating Detonation Engine

Detonation engines have higher thermal efficiency than conventional engines. It is capable of shortening the combustor since the combustion process of detonation completes in quite a short time. Therefore, many researches on detonation engines have been conducted around the world. An RDE can be used as a kick rocket motor for deep-space exploration. However, there are some problems to be solved prior to the practical use of an RDE. One of the most critical problems is heat-transfer problem. High heat load in the combustor is expected. Thus, it is necessary to evaluate the heat-transfer characteristics of an RDE. To realize the space use of an RDE, we conducted long-duration combustion tests and vacuum tests. We succeed in 6-second and 10-second operations of an RDE using C/C composites. And from the vacuum tests, thrust performance is evaluated. We achieved 272 s of specific impulse under the low back pressure of 22.0 kPa.

J. Nishimura, K. Ishihara, K. Goto, K. Matsuoka, J. Kasahara, A. Matsuo, I. Funaki, H. Mukae, K. Yasuda, D. Nakata, K. Higashino, H. Moriai

Decaying Modes of Propagation of Detonation and Flame Front in Narrow Channel

Decaying modes of propagation of flame front in narrow channel for acetylene-air mixtures were investigated experimentally using optical methods of diagnostics. Experiments were carried out using an open detonation channel of square cross section with transverse dimension of 3 mm and length of 1000 mm. It was connected to the detonation tube of large diameter 20 mm and length of 3000 mm. Trajectories of propagation of glowing combustion products (streak images) and frames of the reaction zone were obtained. Oscillating form of the propagation of the combustion inside the narrow channel after the decay of the stationary Chapman-Jouguet detonation into the shock wave and the flame front was registered. Parameters of velocity oscillation were obtained. The time interval of oscillations and spatial interval were measured. After the decay of the detonation wave, the average velocity of the flame front decreases first to 1000 m/s and then to 200 m/s. Minimum recorded value of the flame velocity was presented. It was shown that in spite of the substantial thermal losses to the channel walls, the propagation of detonation-like galloping combustion is possible in channels of subcritical size.

S. V. Golovastov, G. Yu. Bivol

Design and Measurement of Injection Gas Concertation in Rotating Detonation Engines via Diode Laser Sensors

For an air-breathing rotating detonation engine (RDE), in practice a relatively low drop of stagnation pressure of combustor and lower losses from air injection/inlet are desirable. A 6 inch diameter RDE running with pressure ratio cross air injection around and less than chocked condition was developed and examined to investigate its operating characteristics. Further, design and measurement of fuel concertation ahead of and downstream the injection surface are being undertaken via tunable diode laser absorption spectroscopy (TDLAS) technique. Experimental results show that the ethylene/air RDE can be operational even though the injection pressure ratio is lower than chocked condition. The TDLAS system was designed to apply Md-IR (3.411 μm) and Near-IR (1.625 μm) diode lasers to scan absorption features of ethylene and CO2 of the product gas, respectively. From these results, one could have a better understanding on local equivalent ratios and their distribution immediately before the arrival of the rotating detonation and study whether the product gas would flow back to the air plenum and their effects on RDE performance, in particular for the engines operating at the relatively low injection pressure ratio. This part of work is being tested and will be reported in the presentation.

Po-Hsiung Chang, Jiun-Ming Li, Boo Cheong Khoo, Lei Li, Jie Ming Teh, Chiang Juay Teo

Investigation of High-Frequency Pulse Detonation Cycle with Fuel Phase Transition

To achieve the pulse detonation (PD) operation at high frequency, it is essential to shorten deflagration-to-detonation transition (DDT). Increasing the initial pressure of detonable mixture is a valid way to solve this problem. Then, we carried out the PD operation at 1010 Hz with the total pressure of supplied oxidizer changed. A combustor having the length of 100 mm and the inner diameter of 10 mm was used, and pure oxygen and supercritical ethylene were used as propellant. The PD operations at 1010 Hz were successful, and the decrease of DDT distance by approximately 50% was confirmed by increasing the initial pressure of detonable mixture by 242%. In addition, PD operation at higher frequency was demonstrated. With a combustor which has the length of 60 mm and the inner diameter of 10 mm, seven-cycle PD operation at 1916 Hz was carried out, and the average of measured flame propagation speed was in good agreement with the estimated detonation speed.

H. Taki, K. Takao, N. Hirota, K. Matsuoka, J. Kasahara, H. Watanabe, A. Matsuo, T. Endo

Numerical Study of Hydrogen–Air Detonation in Vibrational Non-equilibrium

The effects of vibrational non-equilibrium and vibration–chemistry coupling on hydrogen–air detonation are numerically investigated by solving reactive Euler equations coupled with a multiple vibrational temperature-based model. Detailed hydrogen–air reaction kinetic is utilized, Landau–Teller model is adopted to solve the vibrational relaxation process, and the coupled vibration–chemistry vibration model is used to evaluate the vibration–chemistry coupling. It is shown that the relaxation process and vibration–chemistry coupling considerably influence the hydrogen–air detonation structure, highlighting the importance of correct treatment of vibrational non-equilibrium in detonation simulations.

L. S. Shi, P. Zhang, C. Y. Wen, H. Shen, M. Parsani, D. L. Zhang

Aerodynamic Force Measurement in a Large-Scale Shock Tunnel

Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5 to 9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests used in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model, and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor, which can be applied in the force measurement that 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12, and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time.

Yunpeng Wang, Yunfeng Liu, Changtong Luo, Zonglin Jiang

Trial Implementation of TiN Surface Coating for a Main Piston Towards Reducing the Opening Time for a Diaphragmless Driver Section

In this study, we have performed TiN coating for a free piston to decrease the abrasion resistance between the free piston and a housing, consisted of a main piston. The thickness of the TiN layer on the surface is 2 μm. The opening time of the main piston is measured by using the surface-coated free piston. As a consequence, the opening time of the main piston is achieved 500 μs for 2 mm stroke. Additionally, the shock wave has been generated in the glass tubes with 2, 3, and 4 mm diameter to confirm the shock wave propagation. The shock wave measurements are performed at the several points along the axial direction of the tube by using laser differential interferometer. Consequently, the shock wave propagation is confirmed by using the surface-coated free piston. Moreover, the experimental efficiency is drastically improved especially at the initial experimental process. However, TiN coating partly disappeared by repeated use.

S. Udagawa, W. Garen, T. Inage, M. Ota, K. Maeno

Aerodynamic Force Measurement Techniques in JF12 Shock Tunnel

An aerodynamic force test was conducted in JF12 long-test-time shock tunnel. The test time of JF12 is 100–130 ms. The nominal Mach number is Ma7.0 and the exit diameter of the contoured nozzle is Ф2.5 m. The total enthalpy is 2.5 MJ/kg which duplicates the hypersonic flight conditions of Ma 7.0 at 35 km altitude. The test model is the standard aerodynamic force model of 10° half-angle sharp cone. The length of the test model is 1.5 m and the weight is 57 kg. The aerodynamic forces were measured with a six-component strain balance. The experimental results show that in the 100–130 ms test duration, the signals of strain balance have 3–4 complete vibration cycles. The aerodynamic force coefficients of JF12 are in good agreement with that of conventional hypersonic wind tunnels. This research demonstrates that aerodynamic force test can be conducted in shock tunnel with test time longer than 100 ms.

YF. Liu, YP. Wang, CK. Yuan, CT. Luo, ZL. Jiang

Optimising the X3R Reflected Shock Tunnel Free-Piston Driver for Long Duration Test Times

The X3R free-piston reflected shock tunnel is an alternate operating mode of the existing X3 expansion tube facility at The University of Queensland, which has been funded by Australia’s Defence Science and Technology Group to provide ground testing capability for the full-scale HIFiRE 8 scramjet engine. Given X3R’s origin as an expansion tube, its relatively short driver compared to its shock tube introduces unique design constraints during its condition development process, requiring careful tuning of the free piston to maximise the available test time. This paper details the ideal and equilibrium gas shock interactions required to provide the candidate Mach 7, 50 kPa dynamic pressure nozzle exit flow, the trends that arise as part of the driver composition selection and optimisation process, the free-piston tuning analysis used to maximise X3R’s driver supply time given its short driver, and the modelling and analysis of facility operation using one-dimensional computational techniques.

S. Stennett, D. E. Gildfind, P. A. Jacobs

Development of a Total Enthalpy and Reynolds Number Matched Apollo Re-entry Condition in the X2 Expansion Tunnel

This paper reports on the development of an expansion tunnel condition based on the peak heating point of the Apollo 4 trajectory. Particular emphasis is placed on replicating the total enthalpy and post-shock Reynolds number of the flow such that representative re-entry heating rates are generated. An analytical state-to-state facility model, PITOT, is used to perform the initial condition design using a secondary driver to increase performance. Deviations from ideal theory are seen when performing initial experiments, and no performance gain was evident using the secondary driver, possibly due to the thick Mylar secondary diaphragm. Nonideal facility performance is assessed and incorporated into the modelling whereupon a condition is chosen that closely matches the desired flow properties.

T. G. Cullen, C. M. James, R. J. Gollan, R. G. Morgan

Liquid-Coupled Dual Piston Driver for Small-Scale Impulse Facilities

This paper describes initial visualisation experiments performed using a novel small-scale impulse facility, driven by two liquid-coupled pistons to provide rapid compression of gas in the driver tube and a sufficiently small shock tube diameter to not require a diaphragm. The facility is designed to be able to investigate the heat transfer behaviour of rapidly compressed gases at small physical scales. We present the design of the facility, comparison between predicted and measured piston motion and high-speed schlieren imaging of the resultant subsonic jet, using carbon dioxide as the test gas. The piston speed and displacement were much smaller than expected, due to the fit of the o-rings on the lower piston to the inner bore of the compression tube being too tight to allow free movement of the lower piston.

S. O’Byrne, R. McCormack, H. Kleine

Initial Testing of a 2 m Mach-10 Free-Piston Shock Tunnel

A large-scale free-piston shock tunnel has been built in China Academy of Aerospace Aerodynamics (CAAA). The diameter of the nozzle exit is 2 m and the length is 12.4 m. The large-scale free-piston shock tunnel is called FD-21, which employed three running modes, such as conventional shock tunnel running mode, high-enthalpy shock running mode, and long-time running time mode. Conventional shock tunnel had finished to debug in 2016, which could provide fine flow quality. Calibrated rake and sharp cone model had been measured. High enthalpy shock runing tube is driven by free piston, which is been operating and soon will be accomplished. Next, the main structure of the FD-21 should be changed, shock tube will be divided into two parts, and third diaphragm will be installed between the two parts.

Junmou Shen, Handong Ma, Chen Li, Xing Chen, Bi Zhixian

CFD Evaluation and Experiment Test of the Running Time of the Ludwieg Tube Quiet Wind Tunnel

The running time of the hypersonic Ludwieg tube quiet wind tunnel is very important to simulate the quiet flow field in the test section, which could contribute to rational utilization of the limited available time and affect the confidence coefficient of the data in the hypersonic transition experimental investigations. Thus, more knowledge on that processes could help to understand the running mode of the Ludwieg tube quiet tunnel and the propagation principle of the expansion wave series. To verify our computational method, the same parameter of the BAM6QT (the Boeing/AFOSR Mach-6 quiet tunnel at Purdue University) is used to compute, and it is agreed with our computational results. At the same time, the Mach4 of the nozzle is designed and built; the time of the flow stream is calibrated.

Junmou Shen, Ying Zhang, Dan Wang, Ruiqu Li, Jian Gong

Development and Performance Study of Shock Tube with Extended Test Time for Materials Research

This work focuses on the development of three unique types of high vacuum shock tubes for materials research. Shock tubes of various types such as simple material shock tube (MST), with extension (MST-E) and with reduction (MST-R) are studied. The major aim of this paper focuses on the augmentation of test time (t IE), reflected shock pressure (P 5), and temperature (T 5) and to get an ideal shock strength for material interaction. The simple MST has a 2.1 m driver and 5.1 m driven sections of inner diameter 80 mm, MST-E has a driver extension of 2.3 m long, and MST-R is equipped with an area reduction at the end of the driven section having a convergent nozzle for shock focusing with an addition of 1.2 m long tube. All the experiments are performed with air as a test gas at 1.0 bar. The experimental results show a variation of tIE of about 10% between the simple MST and MST-E. The MST-R shows an increase of P 5 and T 5 of about 60% and 15%, respectively, in the presence of air. Experimental results are compared with the 1-D normal shock relations (NSR) and KASIMIR software for validation. The results also show about 10–40% discrepancy between experiments and the various tools in all configurations. The experimental and theoretical results of all the three shock tube configurations are discussed in this paper.

Jayaram Vishakantaiah, Gowtham Balasubramanian, Subba Rao Keshava

Measurement of Temperature Field Around Spiked Bodies at Hypersonic Mach Numbers

An investigation of a high enthalpy hypersonic flow has been made over an axisymmetric spiked body at a Mach number of 10.06. Temperature being one of the important physical quantities in hypersonic flows over such variable drag devices, this work aims at characterizing temperature in the shock layer for one such body. A flat-faced cylinder, with a diameter of 70 mm, and a conical nose spike of length 70 mm, screwed into it, were used for the experiments at zero angle of incidence. A well-established technique, the two-color ratio pyrometry (TCRP), has been used for temperature characterization using a DSLR camera. The results were in good agreement with the temperature predicted in the stagnation region by the STN (shock tube and nozzle calculations for equilibrium air) code.

Sneh Deep, Yedhu Krishna, Gopalan Jagadeesh

Three-Dimensional Laser Interferometric CT Density Measurement of Unsteady Flow Field Around a Cylinder Induced by Discharged Shock Wave from a Cylindrical Nozzle

The study of shock wave is of significance in understanding supersonic flow. In this paper, we describe about the three-dimensional (3D) quantitative density measurement technique of unsteady and discharging shock waves. In the experimental research areas, the supersonic unsteady flow fields have been commonly observed by qualitative and two-dimensional (2D) visualization methods, such as shadowgraph, color schlieren, or 2D interferometric images. On the other hand, holography and computed tomography (CT) methods have been applied to the measurement of three-dimensional flow fields. The unsteady flow field around a cylinder by discharging shock wave from a cylindrical nozzle was successfully reconstructed by algebraic reconstruction technique (ART).In this study LICT technique is applied to observe more complex flow field than our previous study induced by discharging unsteady shock wave around a cylinder from a cylindrical nozzle. Three-dimensional flow fields are reconstructed by ART. The obtained results and features of high-speed and unsteady flow field will be discussed.

D. Aoki, S. Nakazawa, K. Kurihara, M. Ota

Curved Shock Wave Propagation in Environment Stratosphere by Laser Ablation

The technique of material removal from a solid target, called laser ablation, is used for a number of industrial applications, particularly in laser propulsion. When a solid surface is irradiated by an intense laser beam, the target surface is heated and ablated, which creates the impulse for the target in opposite direction. The ablated material interacts with ambient gas and then creates the curved shock wave around the target. By using Nd:YAG laser as an ablation source, the shock wave propagation in the stratosphere environment is studied experimentally. As a result, the shape and energy of shock wave show the difference due to the reduction of pressure. The impulse generated by laser ablation is found being insensitive in low ambient pressure.

D. T. Tran, C. Xie, K. Mori

Hypervelocity Test with a Detonation-Driven Expansion Tube

A shock-expansion tube/tunnel is a ground-based test facility to generate hypervelocity test flows for the study of atmospheric reentry physics. Such a high enthalpy test flow features thermochemically non-equilibrium which may lead to critical difficulties in flow diagnostics and measurements. In addition, the test time of such an impulse facility is extremely short which implies a requirement of transducers with high-frequency response capability for model tests or flow diagnostics. In the present work, computations for non-equilibrium reacting flow are conducted to diagnose the key flow parameters and evaluate the test flow for facility upgrading. A conic nozzle is appended to the original facility and to obtain a larger test section and larger Mach numbers. Further experiments are conducted to visualize the overall flow structures over the test models by self-illumination of radicals at high-energy states post strong shock waves. The heat flux at the stagnation point is measured with specially designed thermal couples.

Z. Hu, K. Zhou, J. Peng, Z. Jiang

Shock Shape Transition on Spherically Blunted Cones in Hypersonic Flows

Spherically blunted cones are commonly utilized as re-entry or entry capsules. Depending on the cone angle, the shock shape is either dominated by the spherical nose or the conical part. In flight a transition between these two situations might occur, and this can result in undesirable effects on the aerodynamic stability. To understand the shock shape transition behaviour in more detail, a systematic numerical and experimental study is ongoing. In the present article, the influence of vibrational non-equilibrium compared to frozen flow is discussed for sphere-cone configurations at zero-degree angle of attack.

J. Martinez Schramm, K. Hannemann, H. G. Hornung

Catalytic Recombination Characteristics of Atomic Oxygen on Material Surface by Optical Emission Spectroscopy

Catalytic recombination of atomic oxygen, the main species of air ionization, on heat shield material surfaces was studied in a microwave plasma flow reactor. The atomic oxygen concentration profile above material samples was nonintrusive measured by optical emission spectroscopy. The catalytic recombination coefficients on material surfaces were deduced by the diffusion equation. The catalytic recombination coefficients for the heat shield materials at high temperature obtained in the present experiment are very important parameters for thermal shield design of space vehicles.

X. Lin, S. Wang, F. Li, S. Zhang, X. Yu

Influence of Dual Ignition on Test Conditions of a High-Enthalpy Shock Tunnel

The forward mode is usually chosen to achieve high-enthalpy flows for a detonation-driven shock tunnel. In this paper, the dual-ignition system was developed to burst a metal diaphragm without its fragmentation under the forward operation mode. The influence of delay time on the test conditions of the high-enthalpy shock tunnel was investigated numerically. Results showed that the delay time should be set exactly, or it would affect the performance of the shock tunnel using the dual-ignition forward driving mode, i.e., the effective test or the stagnation temperature. The larger the delay time, the closer the CJ plane propagates to the primary diaphragm, the better consistent with the forward mode.

Q. Wang, W. Zhao, J. W. Li, J. P. Li, P. Lu, Z. L. Jiang

Ablation Measurements in a Low-Density Heat Shield Using Ablation Sensor Unit (ASU)

The detection performance of an ablation sensor, named Ablation Sensor Unit (ASU), which can measure surface recession, thermal decomposition of resin, and temperature of an ablative heat shield material, is demonstrated. A test specimen with embedded ASU is heated using a JAXA 750 kW arcjet wind tunnel facility under one operational condition. The amount of surface recession and char depth and temperature obtained by ASU are compared with the posttest measured values for the recovered test specimen and the surface temperature obtained by a two-color thermometry. The comparison shows that ASU is promising for a simultaneous and an in situ measurement of the ablation phenomena for the ablative heat shield.

Y. Dantsuka, T. Sakai, K. Iwamoto, Y. Ishida, T. Suzuki, K. Fujita

Driver Condition Development for High-Enthalpy Operation of the X3 Expansion Tube

At the University of Queensland (UQ), there are two expansion tubes, X2 and the larger X3. In the past years, there have been many experimental campaigns investigating radiation in high-enthalpy flows in X2. X3 has not been used for similar experiments, although it is larger, it has been undergoing an extended period of upgrades and development, including a new lightweight piston and reservoir extension. This paper reports the progress made in developing high-enthalpy operation in X3 that will be used for future high-enthalpy experimental campaigns.

A. Andrianatos, D. E. Gildfind, R. G. Morgan

Calculation of Intensity Profiles Behind a Shock Wave Traveling in Air at Speeds Exceeding 12 km/s

This paper presents the recent efforts in computing the flow field and radiation behind a shock wave traveling in air at speeds exceeding 12 km/s to support the exploration mission currently considered at JAXA. The influence of the electron number density on the thermodynamic properties and ionization equilibrium constants was highlighted and quantified. The thermochemistry model in JAXA CFD code was upgraded and the flow field was computed. The populations of the excited states radiating in the vacuum ultraviolet (VUV) were computed with a collisional-radiative (CR) model. Subsequently, the radiative properties of the strongest radiators were computed with the models and database of JAXA spectral solver. The computed VUV post-shock intensity profiles were compared with shock-tube radiation measurements obtained in facilities operated at representative flight conditions. The influence of electron-impact excitation and radiative processes is discussed.

A. Lemal, S. Matsuyama, S. Nomura, H. Takayanagi, K. Fujita

Revisiting Temperature Measurements at the Focus of Spherically Converging Shocks in Argon

In this work, temperature measurements at the focus of spherically converging shock waves (CSWs) in argon are revisited. Spherical shock waves are produced inside a conventional circular shock tube, where initially plane shocks are transformed into spherically shaped shocks inside an axisymmetric smoothly converging section. As the CSW reflects from the window, the conditions become extreme so that the gas intensively glows. The light flash collected through the window by optical fibers is separately transferred into a diagnostic setup including a spectrometer. The gas temperature at the cone tip is then deduced from Planck’s fit to the registered radiation spectrum. Maximum temperatures of order of 30,000 K are thus measured.In this study 1D axisymmetric numerical simulation accounting for nonideal gas effects (excitation, Coulomb interaction, ionization, and radiation) assuming equilibrium is employed to study the details of the shock implosion. The prominent advantage of the numerical approach over approximate method used in (Liverts M, Apazidis N, Phys Rev Lett 116: 014501, 2016) is that the calculation can be extended to trace the behavior of the gas behind the reflected (diverging) shock that inevitably dictates the temperature dynamics at the implosion focus. As a result, a comparison between calculations and experimental data demonstrates an improved agreement.

M. Liverts, N. Apazidis

Influence of Matrix Resin on Impact Resistance of CFRP by a Small Sphere

Since carbon fiber-reinforced plastic matrix composites (CFRPs) have the advantages of lightweight and high strength, they are promising candidates for structural materials of high-speed vehicles/aircrafts. With such use, foreign object impact is an inevitable risk for the materials; damage behavior or tolerance should be evaluated. Using several kinds of CFRPs with different matrix resins, epoxy and polyamide 6, a spherical projectile was impacted against the CFRPs to evaluate the effects of the matrix resins on the deformation behavior and debris amount. A high strain-to-break fiber and low-modulus matrix results in a higher dissipation energy with a larger deformation but lower amount of debris. The PA6 matrix composites, when having similar mechanical properties of the epoxy resin matrix composites, exhibit a similar behavior against spherical projectile impact regarding the deformation, debris amount, and dissipation energy.

T. Kawai, T. Irisawa, Y. Tanabe, M. Nakayama, A. Yoshimura

Improvement of Impact Resistance of Ceramics by Using Resin-Based Materials

Since ceramics are lightweight and have a sufficient strength, they have the potential to be used as a shield material. However, their low fracture toughness and low shape imparting inhibit their actual applications. To overcome the low fracture toughness and low shape imparting, layered structures joined with resin-based adhesives were conducted for use as protection against projectile impact. As the joining layer, a certain thickness above a certain level seemed to be required. No clear effects could be seen by changing the resin’s composition and type. A backup plate, even thin, effectively reduced the debris scattering from the layered structures.

S. Yamashita, T. Suzuki, S. Fujimori, T. Irisawa, Y. Tanabe

Measurement of Plasma Formed by High-Speed Impact to Estimate Temperature at Impact Point

Structures in space are at the risk of collision with space debris, motivating the study of high-speed impact phenomena. In high-speed impacts, the temperature increases rapidly at the impact point, possibly causing destruction at the impact point in addition to impact pressure. However, the influence of high temperature has not been elucidated because existing thermometers do not have sufficient time resolution to measure the increasing temperature at the impact point. In this study, plasma formed by high-speed impact was measured and observed to estimate the temperature at the impact point. High-speed impact experiments were performed using a gas gun to form plasma. A projectile impactor and target were made of aluminum alloy, and the projectile velocity was approximately 650 m/s. High-speed images and high-speed optical visualization images of the state of plasma diffusion were acquired using a high-speed camera. In the experiments, the electron temperature of the plasma was measured by employing the triple probe method, and it was confirmed that high-speed optical visualization images are useful for observing plasma diffusion behavior.

Y. Motoyama, K. Umeda, T. Sakai, S. Kinoshita, K. Watanabe

Application of Riemann Solver for Compressible and Non-Expanding Fluid to Impact on Regolith

The compressible and non-expanding (CNE) fluid model was applied to the numerical simulation of the high-speed impact of the regolith-like granular material. Assuming the different speeds of sound for the irreversible compression and reversible elastic unload/recompression processes, this model can describe the following features: (1) high-density fluid remains after all the motion stops, (2) the absence of the fluid, that is, the vacuum is allowed to exist, and (3) the crack can be formed in place of the expansion wave. The fundamental solutions of the Riemann problem, which are necessary for Godunov’s method, are composed of the shock waves in the elastic process, the shock waves with the irreversible compression, the contact discontinuities, and the contact surfaces with the vacuum. The shock wave in the elastic process appears as the precursor to the irreversible compression. The numerical results of the one-dimensional regolith-on-regolith impact problems revealed that the phenomena are divided into the penetration stage and the bounce back stage. The ejection velocity decreases with the increase in the speed of sound for the unload process. In the two-dimensional oblique shock wave problems, the two-stage shock wave structure composed of the precursor wave and the irreversible compression wave was numerically simulated, and the relation between the wedge angle and the wave angles was obtained.

K. Suzuki

Mathematical Modeling of the Impact of High-Speed Metallic Plates

The paper is devoted to the mathematical modeling of the problem of two metal plates impact using two approaches. In the first approach, the problem is solved using three-dimensional Euler equations and the stiffened gas equation of state for the media. The parameters of the equation of state are calibrated using wide-range equations of state computations of the parameters of shock waves which form after the impact. The second approach is based on one-dimensional two-fluid seven-equation model. In simulations of metal plates impact, we get two shocks after the initial impact that propagate to the free surfaces of the samples. The characteristics of shock waves are close (maximum relative error in characteristics of shocks is not greater than 7%) to the data from the wide-range equations of states computations.

S. Fortova, P. Utkin, V. Shepelev, T. Kazakova

Study of Shock Impact Pressure Amplification and Attenuation of Acoustic Waves in E-Glass Material

In this paper we present the amplification of shock pressure and attenuation of acoustic emission (AE) due to the impact of shock waves on multilayer E-glass armor materials having density of about 2000 kg/m3 with thickness of 5 mm and 10 mm. Shock tubes are well known to produce desired shock strength for material interaction. In this work the E-glass material is made to interact with strong shock wave produced from material shock tube (MST). The peak pressure amplification at the back wall is caused by the transfer of gas momentum to the material mass. The 5-mm- and 10-mm-thick E-glass material shows the amplification of 10 and 3 times, respectively, with respect to the incident front-wall pressure at different Mach numbers. The AE is generated by sonic boom at the open end of the diaphragmless shock tube (DST). A constant shock Mach number of 1.3 is produced in the DST to study the attenuation characteristic of E-glass material. The E-glass materials were placed at different distance from the open end of the shock tube at an angle of 30° at either side of the shock tube axis to study the attenuation of AE. The result shows attenuation of about 42–4% for 5 mm and about 85–52% for 10 mm E-glass materials.

Jayaram Vishakantaiah, R. K. Kannan, G. Raj Arvind, K. P. J. Reddy

Computational Modeling of Recoilless Weapons Combat Training-Associated Blast Exposure

Military personnel are routinely exposed to blast as part of routine combat training with shoulder-fired weapons. Scientific, medical, and military leaders are beginning to recognize that use of shoulder-fired weapons may result in acute and potentially long-term physiological effects. However, the back blast generated from shoulder-fired weapons on the weapon operator has not been well characterized. By quantifying and modeling the full-body blast exposure from these weapons, better injury correlations can be constructed.Blast exposure data from the Carl Gustav and Shoulder-Launched Multipurpose Assault Weapon (SMAW) were used to reverse engineer source terms for computational simulations of blast exposure on operators of these shoulder-mounted weapon systems. A propellant burn model provided the source term for each weapon to capture blast effects. Blast data from personnel-mounted gauges during routine training was used to create initial, high-fidelity 3D computational fluid dynamic simulations using SHAMRC. These models were then improved upon using data collected from static gauges positioned around the individual weapons systems. The final simulation models for both the Carl Gustav and SMAW were in good agreement with the data collected from the personnel-mounted and static pressure gauges. Using the final simulation results, contour maps for peak overpressure and peak overpressure impulse on the gunner and assistant gunner for each weapon system were then created.Reconstruction of the full-body blast loading enables a more accurate assessment of blast exposure which could be used to correlate with injury. By accurately understanding the blast exposure and its variations across an individual, more meaningful correlations with injuries including traumatic brain injury can be established. As blast injury thresholds become better defined, results from these reconstructions can provide important insights into approaches for reducing risk of injury to personnel operating shoulder-launched weapons.

S. Wiri, A. Ritter, J. Bailie, C. Needham, J. Duckworth

Contribution of Cavitation Generation to Shock Wave Sterilization Effects in a Narrow Water Chamber

The paper reports on the generation mechanism of cavitation bubbles in a narrow water chamber and the sterilization effects of these cavitation bubbles on marine bacteria. Underwater shock waves are generated by electric discharge. Propagation behaviors of the waves in the water chamber are investigated using an optical method. On the other hand, a bio-experiment with marine bacteria is also carried out to examine sterilization effects. It is found that the shear wave is produced in the wall material of the water chamber by the energy release of underwater electric discharge and results in the tensile stress arising in the water, and thereby cavitation bubbles are induced with the propagation of the shear wave. From the results of the bio-experiments, we confirm a high sterilization effect of the cavitation bubbles.

J. Wang, A. Abe, T. Koita, M. Sun

Shock Waves Confer Immunity Against Infections in Mice

Shock waves are essentially nonlinear waves that propagate at supersonic speeds. Any sudden release of energy will result in the formation of shock waves. Personnel at the war fields are constantly exposed to shock waves generated by bombarding ammunition. The short-term and long-term effects of this exposure on various systems of the body are not clearly understood. In this study, we have shown for the first time that shock wave exposure confers protective immunity in a murine model. We have tested this with Salmonella typhimurium in Balb/c mice. War field conditions were mimicked in the laboratory using the diaphragmless shock tube. Infection challenges post shock wave exposure were evaluated by checking the organ load of Salmonella in the spleen, liver, and mesenteric lymph nodes. It was found that the bacterial load in these organs was significantly lower as compared to the control group of animals. The mechanism of this phenomenon was also addressed by measuring the cytokine levels in serum of the animals. It was observed that the proinflammatory cytokine expression is enhanced after exposure to shock waves. In a nutshell, we show that shock waves can induce protective immunity against infections by altering the levels of proinflammatory cytokines.

Akshay Datey, Dipshikha Chakravortty, Gopalan Jagadeesh

On the Relation Between the Shock Wave Thickness in Biomaterials and the Threshold for Blast-Induced Neurotrauma

It is found that the threshold for blast-induced neurotrauma documented from previous experiments in animals and cell cultures is approximately given by the criterion that the shock thickness be comparable to the characteristic dimension of a neuron cell (approximately 20 μm). The coincidence of the shock thickness with the characteristic dimension of the neuron cells supports the view that cell damage may be related to the localized mechanical deformation of cell components and shear for sufficiently strong and thin shocks. Our estimate of the shock wave thickness in biological material is based on the weak shock model of Thompson extended to materials whose compressibility can be modeled using the stiffened gas equation of state. Simulations of the transient relaxation of step function shocks into the steady shock profiles provided the time scale for the shock thickening when an impact-generated shock or much thinner air shock enters the biomaterial modeled. We find that air shocks will always be more damaging than those propagating through water at the same pressure level, consistent with experiment.

M. I. P. Radulescu

Development of a Miniaturized Focused Shock Wave Generator for Medical Application

This paper reports the result of development of a miniaturized focused shock wave generator for a technological innovation in minimally invasive therapy. The focused shock waves generated from the tip of the shock wave ablation catheter reached 80 MPa of peak pressure and successfully damaged a slab of fresh potato. The depth of damaged area and the pulse laser energy were related to positive correlation. These results indicate the potential usefulness of our new shock wave ablation system.

H. Yamamoto, K. Takayama, H. Shimokawa

Intracellular Ca2+ Increase Evoked by Single Acoustic Pulses

Shock wave therapies require cellular responses. However, how shock waves interact with cells remains elusive. In this study, it was asked whether pressure discontinuities at wave fronts of shock waves are indispensable for evoking cellular responses. With shock wave irradiations, intracellular Ca2+ increase was evoked in endothelial cells. This cellular response was independent of pressure increment at front of shock waves. These results suggest that pressure discontinuity at wave front is not indispensable for evoking the cellular response.

A. Tsukamoto, T. Takahashi, S. Tada, K. Nakagawa

A New Device for Crossing Chronic Total Occlusions

We report on the design and testing of a new minimally invasive device for crossing chronic total occlusions in the coronary and peripheral vasculature. The device is based on a novel shock wave generator that exploits inverse dispersion in solid waveguides to amplify the signal of broadband piezoelectric ultrasound transducers. Results of tests assessing the safety, efficacy, and mechanism of action of the device on a variety of surrogates, ex vivo arteries, and live animals are presented.

L.-P. Riel, S. Dion, M. Charlebois-Ménard, M. Brouillette, S. Bérubé, M.-A. Despatis, A. Benko, M.-É. Clavet, M.-J. Bertrand, P. Geoffroy, J.-F. Tanguay

Biological Effect of Shock Waves: Mechanism of Blast-Induced Traumatic Injury to Medical Application

Shock waves (SW) have been applied to a variety of medical treatments. Recent studies have focused on applications within microenvironments. On the other hand, blast-induced traumatic injury (bTBI) became a social problem after the Iraq and Afghanistan conflict, and SW is gaining attention to understand the mechanism of primary bTBI. This paper reports a preliminary experimental result of SW propagation in simulated biomedical materials for understanding mechanism of both potential complication of medical application of SW within the cranium and bTBI. SW, generated by detonating of a 10 mg silver azide (AgN3) pellet, was interacted with a brain model using simulated biomedical materials. The process of SW interaction with a brain model was visualized by shadowgraph method and recorded by a high-speed video camera. The pressure history in a brain model was measured by a polyvinylidene fluoride needle hydrophone. The present experiment showed occurrence of complex wave front at specific location within the chamber and indicated the importance of understanding SW propagation effect when applying SW above certain overpressure. We will also summarize current research of complication of SW medical application and also bTBI.

A. Nakagawa, K. Ohtani, T. Kawaguchi, T. Tominaga

Toward Noninvasive Drug Injection via Control of Laser-Induced Breakdown in Liquid

A microjet with a maximum speed of 300 m/s and a diameter of 150 μm is ejected from a nozzle by the pulsed laser-induced bubble expansion. At every pulse of laser irradiation in the driving chamber, adverse air bubble growth has been a major issue in sustaining a uniform jet speed and overall performance of drug delivery. Here, a check valve is introduced to the drug chamber for controlling the flow dynamics inside and thus preventing ambient air from entering the nozzle. The newly designed valve in the laser-induced microjet injector proves that constant jet speed is possible regardless of the number of laser pulses, which allows the penetration of porcine skin to reach a depth well beyond 1.5–2.25 times the previously attained depths.

H. Ham, S. Yeo, H. Jang, J. J. Yoh

Current Trend in Cell Membrane Manipulation by Ultrasound and Underwater Shock Wave

The paper presents our recent findings in reparable cell membrane manipulation by ultrasound and underwater shock wave. We introduced innovative in vitro methods including free suspension and capillary micro-gripping systems equipped with micro transducers to achieve the maximum level of experimental flexibility for capturing real-time highly magnified images of cell-microbubble interactions. Insonation of single cells and microbubbles parallel with high-speed microphotography and fluorescence microscopy allowed us to identify dynamic responses of cell membrane to microbubble streaming dynamics in correlation with sonoporation. Our results showed that bubble oscillation in close contact with the cell membrane can cause local deformation and transient porosity in the cell membrane with minimum cell toxicity.

S. F. Moosavi-Nejad, H. Hosseini

Analysis of Deformation Process of a Bubble in an Elastic Capsule by Shock Waves and Their Medical and Biological Applications

This paper describes culture regeneration system combining cultivation promotion and capsule destruction using shock wave, especially the basic mechanism for its development such as deformation process of a bubble in a microcapsule composed of membrane, liquid, and gas bubble. Necessary tasks to optimize the improvement of cell culture rate and the microcapsule disintegration rate by pressure control are (1) investigation of the influence of amount of gas bubbles and pressure waveform on the threshold of capsule destruction due to bubble collapse and (2) estimation of threshold of pressure for the collapse. It is concluded that (1) maximum amplitude of bubble, which corresponds to the degree of damage, is decreasing as the gas ratio is increasing, and (2) maximum amplitude of bubble is also decreasing as the duration time becomes smaller order.

M. Tamagawa, T. Imakado, R. Ogasahara

Shock Waves Can Cure Biofilm Infections In Vivo in Combination with Antibiotics

Shock waves are essentially non-linear waves that propagate at supersonic speeds. Any sudden release of energy will result in the formation of shock waves. In this study, we have shown for the first time that catheter, skin and lung biofilm infections can be treated using shock waves combined with antibiotics. Many bacteria secrete a highly hydrated framework of extracellular polymer matrix on encountering suitable substrates and embed within the matrix to form a biofilm. Bacterial biofilms are observed on many medical devices and on epithelial and endothelial surfaces during infection. For endocarditis, periodontitis and lung infections in cystic fibrosis patients, biofilms are an important mode of growth. Bacteria within the polymeric hydrogel matrix are protected from antibiotics, and antibiotic concentration of more than 1000 times of the MIC may be required to treat these infections. Here, we have demonstrated that shock waves can be used to remove Salmonella, Pseudomonas and Staphylococcus biofilms in urinary catheters. The studies were extended to a Pseudomonas chronic pneumonia lung infection model and Staphylococcus skin suture infection model in mice. The biofilm infections in mice, treated with shock waves, became susceptible to antibiotics, unlike untreated biofilms. Mice exposed to shock waves responded to ciprofloxacin treatment, while ciprofloxacin alone was ineffective in treating the infection. These results clearly demonstrate for the first time that shock waves, combined with antibiotic treatment, can be used to treat biofilm formation on medical devices as well as in situ infections.

Akshay Datey, Divyaprakash Gnanadhas, Dipshikha Chakravortty, Gopalan Jagadeesh

Simulation of Shock-Bubble Interaction Using a Four-Equation Homogeneous Model

This paper presents a numerical study of air bubble collapse in water induced by the impact of a shock wave. Simulations are performed using an inviscid compressible one-fluid solver. Numerical results are displayed for single-bubble and twin-bubble cases in order to investigate the evolution of the maximum pressure during the collapse. The influence of the distance between bubble is also investigated.

Eric Goncalves, B. Dia Zeidan

A Study of Dispersion, Vaporization, and Combustion of Burnable Liquids Surrounding Charges

A complex numerical simulation where blast waves interacted with a liquid, burnable simulant inside a chamber was conducted. The liquid simulant was dispersed by a small high explosive (HE) charge and then impacted by the blast wave produced by a significantly larger HE charge. The physics of the problem required numerical tools that allowed for (1) coupling of compressible and near-incompressible (+VOF) solvers, (2) a dropletization model by liquid bulk dispersion, (3) droplet breakup and vaporization, (4) a chemical package for combustion, and (5) a particle update technique. The resulting numerical code successfully simulated the scenario, and the predicted pressure agreed excellently with the measured data.

F. Togashi, J. D. Baum, O. A. Soto, R. Löhner, J. Bell

Multi-scale Simulation of the Interaction of a Shock Wave and a Cloud of Particles

A multi-scale method is proposed in which resolved mesoscale simulations of the interaction of a normal moving shock with a rectangular cloud of particles yield a parametric representation of the drag due to these particles. This establishes a link between the meso- and macroscale through metamodels, which provide closure terms for a macroscale model. The latter is used to simulate a process-scale problem via an Eulerian-Lagrangian approach, assuming a point-particle representation of the particle phase. Results obtained using a traditional cloud-in-cell method with first-order particle-to-grid weighing are compared to those of the novel “SPARSE” algorithm which represents the entire particle cloud with a single macro-particle and approximates the actual cloud shape with a bivariate Gaussian distribution for the purpose of weighing the particle momentum and energy contribution to the carrier flow onto the Eulerian fluid grid. The resulting multi-scale approach has the potential to improve the accuracy and efficiency of shocked particle-laden flow simulations and enable simulation of realistic scales.

S. Taverniers, G. B. Jacobs, V. Fountoulakis, O. Sen, H. S. Udaykumar

Surface Jetting Induced by Explosion in Liquid Below an Immersed Bubble

The surface jets induced by an explosion below an immersed gas bubble in water are investigated experimentally. Typical phenomena including the bubble evolution and the jet formation are observed through high-speed photography. It is found that the inner jet resulting from the shock bubble interaction is the main cause of the surface jet. The velocity of the surface jet decreases with the initial depth of the bubble, and there exists a maximum bubble depth above which no surface jet occurs.

Y. Zhu, G. Zhang, J. Yang

Generation Frequency of Rebound Shock Waves from Bubble Collapses in Cavitation Jet

In this paper, a method using cavitation jet is proposed to remove marine creatures adhered to the body of a ship. The flow with the cavitation jet is produced using a high-pressure pump and cavitation nozzle with an orifice plate. Rebound shock waves are expected to be continuously generated in the cavitation jet flow. In order to observe the behaviors of the rebound shock waves, experiments are carried out using the Schlieren method in a water tank. From the results of the visualization, it is found the generation frequency of the rebound shock wave reaches its peak at a close position to the nozzle exit. The behaviors of the rebound shock waves are also investigated under the influence of a wall boundary beside a cavitation jet. The results show that the position where the maximum generation frequency is obtained is at several ten times of an orifice diameter from the nozzle exit, and the generation frequency decreases due to the effect of the wall boundary.

K. Nishibayashi, J. Wang, A. Abe

Experimental Study on the Influence of Underwater Explosion Depth on the Disintegration of Thin Resin Plate Attached Microbubbles

This paper reports on the influence of underwater explosion depth on the disintegration of thin polystyrene plate attached microbubbles subjected to the underwater shock wave and the primary bubble induced by the explosion. The underwater explosion is created by the electrical discharge. The thin plate motion caused by the interaction of underwater shock wave and primary bubble with the plate is experimentally investigated and visualized by the shadowgraph method. The effect of explosion depth on the disintegration of plate is discussed by comparing visualized images. It was found that the disintegration of plate was depended on the explosion depth. It was also confirmed that the fragmentation of plate was caused not by the overpressure from microbubble collapse by the underwater shock wave loading but by the interaction of rebounding primary bubble with the plate in the experimental conditions of this study.

T. Koita, M. Sun, Y. Fukushima, L. Guo, X. Zhao, S. Kobayashi

Numerical Study of the Flow Separation in a Rocket Nozzle

The flow separation phenomenon often occurs in large area ratio nozzles of rocket engines, in order to study the relationship between the combustion chamber pressure and the flow separation point and the effect of flow separation on the nozzle. The numerical simulation of nozzle under different chamber pressures is carried out by using computational fluid dynamics (CFD) method. The compressible Navier-Stokes equations are used to calculate the fluid region. One equation Spalart-Allmaras turbulence model is selected. A second-order implicit advection upstream splitting method (AUSM) scheme is employed for the convection term. The flow fields of nozzle under different nozzle pressure ratios are obtained, and the pressure distribution of nozzle and flow separation position are analyzed. The results show that the flow separation point departs from the inlet of the nozzle as the nozzle pressure ratio (NPR) increases. This research can provide a corresponding reference for the design and analysis of relevant nozzle.

S. Zhu, Z. Chen, C. Zheng, H. Zhang, Z. Huang

Hybrid RANS/LES Simulation of Shock-Induced Separated Flow in Truncated Ideal Contour Nozzle

The present study is motivated by the flow analysis of supersonic nozzles used in the rocket launcher, more specifically about the generation of side loads. The work aims at identifying and at modeling the dominant elements of the organized structure of the flow in overexpanded rocket nozzles.

Eric Goncalves, B. Guillaume Lehnasch, C. Julien Herpe

Experimental Study of TICTOP Nozzles

The new nozzle contour concept TICTOP is introduced and its experimental validation is presented. The TICTOP nozzle features a comparable performance like TOP nozzles, whereas reattached flow conditions during transient start-up and shutdown operation are avoided. A hypothesis on the formation of the cap-shock pattern in TOP nozzles is presented.

R. Stark, C. Génin

Three-Dimensional Instability of Shock-Wave/Boundary-Layer Interaction for Rocket Engine Nozzle Applications

A fully three-dimensional analysis is carried out on an overexpanded rocket engine nozzle configuration to investigate the role of the internal shock-induced separation on the mechanism of generation of side loads during start-up and shutdown transients. A hybrid URANS/LES approach based on the delayed detached eddy simulation turbulence model is used. Reasonable good agreement is obtained between numerical and experimental results. The numerical wall-pressure spectrum shows a narrow peak that a dynamic mode decomposition reveals to be associated with a mode whose characteristics resemble the experimental azimuthal mode believed to be the cause of the generation of side loads.

J.-Ch. Robinet, A. Sansica, Eric Goncalves, J. Herpe

Shock Interactions in Thrust Optimised Parabolic (TOP) Nozzles during Start-Up and Shutdown

The separation phenomenon in parabolic nozzles has long been studied in detail and is well documented. The parabolic nozzles are normally being operated in those regimes of pressure ratios where separation does not occur. However, during the start-up and shutdown transience, the operation of the nozzles inherently falls in the separation regimes due to the lower total pressures they experience. The present work is an attempt to study the shock structures in a thrust optimised parabolic (TOP) which occur during the separation process in nozzle and its interaction due to which either a free shock separation (FSS) or restricted shock separation is observed (RSS). The hysteresis of FSS↔RSS transition during the start-up and shutdown transiency is also studied. A complete transient analysis on shock structure interactions in 2D axisymmetric TOP nozzle of area ratio 36 was carried out, and the results were used to interpret the shock interactions, separation patterns and hysteresis effects.

Ijaz Mohamed, G. Rajesh

Shock System Deformation in High Mach Number Rocket Nozzles

Flow overexpansion in supersonic nozzle, with or without flow separation, leads to the formation of a shock system composed of an oblique shock rooted at the nozzle wall and a Mach reflection. A study has been conducted on the shock system deformation for nozzles with high design Mach numbers, i.e., with high wall opening angle. An experimental test campaign was conducted on three cold flow sub-scale nozzles with Schlieren imaging. An important curvature of the Mach disk was demonstrated for the nozzle with the higher design Mach numbers and low nozzle pressure ratio conditions. The experimental observations were confirmed with numerical simulations realized with DLR in-house RANS solver TAU, which showed a sensitivity of the Mach disk shape to radial pressure gradients in the flow in its vicinity. In addition, the experiments indicated instability of the Mach lens at low NPR values, corresponding to a position of the Mach disk in the region of the highest pressure gradient.

C. Génin, R. Stark, S. Karl

Numerical Investigation of a Planar Shock Wave Interacting with an Acentric Water Ring

The droplet breakup and the bubble collapse are typical flow phenomenon involving complicated pressure and density variation as well as interface evolution. In this paper, the numerical simulation of a planar shock wave interacting with an acentric water ring is studied. In order to simulate the spatiotemporal interface evolution of the water ring impinged by a planar shock wave, a quasi-conservative interface capturing method is employed, in which the governing equations consist of the conservative Euler equations and the scalar transportation equations, together with the stiffened gas equation of state of the two phases. An incremental stencil adapted WENO scheme with fifth order in the smooth regions is employed for the spatial reconstruction. The numerical results show that the bubble collapses under different incident Mach number shock waves due to the strong pressure gradients. The strong transverse jets form because of the Richtmyer-Meshkov instability. The jet tip and its impaction on the downward wall of the cavity are extracted by analyzing the isolines ofγrepresenting the two-phase interface. The jet tip speed and the pressure at the impaction point nonlinearly increase with the incident shock wave strength.

Gaoming Xiang, Bing Wang

A Compact High-Order Finite Volume Method for Computing Shock Waves on Arbitrary Grids

A cell-centered finite volume method based on a variational reconstruction, termed FV(VR) in this paper, is developed for compressible flows on 3D arbitrary grids. In this method, a linear polynomial solution is reconstructed using a newly developed variational formulation. Like the least-squares reconstruction, the variational reconstruction has the property of 1-exactness. Unlike the cell-centered finite volume method based on the least-squares reconstruction, termed FV(LS) in this paper, the resulting FV(VR) method is stable even on tetrahedral grids, since its stencils are intrinsically the entire mesh. However, the data structure required by FV(VR) is the same as FV(LS) and is thus compact and simple. A nonlinear WENO reconstruction is used to suppress nonphysical oscillations in the vicinity of strong discontinuities. A variety of the benchmark test cases are presented to assess the accuracy, efficiency, robustness, and flexibility of this finite volume method. The numerical experiments indicate that the developed FV(VR) method is able to maintain the linear stability, attain the designed second order of accuracy, and outperform the FV(LS) method without a significant increase in computing costs and storage requirements.

L. Li, H. Luo, Yuxin Ren

Numerical Modelling of the Effects of Surface Roughness on Blunt Body Heat Transfer

The paper presents the numerical modelling of the effects of surface roughness on heat transfer of high Mach number flow to a blunt body. Computational fluid dynamics (CFD) is pursued using our in-house Clithium2 code for axisymmetric flow of M = 6 impinging on a flat-faced circular cylinder. Laminar and ideal gas conditions are assumed due to the short flow time and low stagnation temperature (<2000 K). Good to excellent agreement is achieved with known results of stagnation flow over flat smooth surface. The heat flux is indirectly calculated using CFD results of boundary layer edge condition due to the layer’s thin thermal thickness. A peak at the cylinder’s face centre is found, where roughness initially causes a decline in the heat flux but an increase at 1000 micron or above. The stand-off distance of the bow shock wave behaved inversely to the heat flux. Real gas effects and the breakdown of the continuum assumption are also discussed for further analysis.

D. Kim, G. Park, E. Avital

Numerical Study of Shock Propagation in Liquid/Gas Media

A semi-conservative, stable, interphase-capturing numerical scheme for shock propagation in heterogeneous systems is applied to the problem of shock propagation in liquid-gas systems. The scheme is based on the volume fraction formulation of the equations of motion for liquid and gas phases with separate equations of state. The semi-conservative formulation of the governing equations ensures the absence of spurious pressure oscillations at the material interphases between the constituents. Interaction of a planar shock in water with a single spherical bubble as well as twin adjacent bubbles and a bubble array is investigated. Several features of the interaction process are studied, including propagation and focusing of the transmitted (refracted) shock within the deformed bubble, creation of a water hammer by a diffracted shock in water, and generation of high-speed liquid jet due to induced flow vorticity in the later stages of the process.

N. Apazidis

CFD Models of Shocks and Flow Fields Associated with Decelerating Spheres in Terms of Flow History and Inertial Effects

The bow shock stand-off distances of a sphere decelerating in air under its own drag were determined through numerical simulations using Fluent. Three cases were investigated with three different initial velocities. These results were then compared to steady-state numerical results obtained from the same CFD code in order to identify differences between the steady and unsteady cases at given Mach numbers. The initial Mach numbers used were 1.13, 1.19 and 1.25. A two-dimensional axisymmetric model was used in conjunction with a viscous turbulence model suitable for analysing transonic external aerodynamic problems. Numerically determined shock stand-off distances were compared to previous experimental results from literature for the steady and unsteady cases. There is a very good agreement between the steady-state numerical and experimental results, which confirms that a suitable numerical model was used. In the unsteady scenario, the numerical results follow the same trend as the experimental results, but the agreement is not as good. Some explanation for this is given. It was found that the shock stand-off distance for the unsteady cases was generally smaller than for the steady-state cases. Also, for the unsteady cases, a bow shock that was formed in supersonic flight transforms into a wave and persists well into the subsonic regime. In the steady-state cases, it is of course well known that no such phenomenon exists in flow at sonic and subsonic Mach numbers. The differences in the flow field and consequently in the drag in the steady and unsteady cases are explained using the concepts of flow history and fluid inertia.

H. Roohani, I. M. A. Gledhill, B. W. Skews

Conjugate Heat Transfer Analysis in a Hypersonic Flow

Transient heat transfer analysis is very significant and has scientific relevance to understand the flow in hypersonic applications. The present studies mainly focus on the effects of experimental time scale and substrate properties on the thermal penetration of the heat into the aerodynamic surfaces. The problem is addressed though conjugate heat transfer (CHT) analysis. The main observation of present analysis is that near the sensor region (stagnation point), heat penetration is less as compared to SiC and carbon-carbon region. Temperature rise is more significant in the sensor region. Stagnation-point heat flux is seen to be largely decreased due to maximum rise in the wall temperature in that region. The CHT analysis has the capability of predicting heating rates at any locations on the aerodynamic surfaces with multiple wall materials and can be used as tool for selection material and design of hypersonic configurations.

Ravi K. Peetala

Laser-Induced Shock Waves in Micro Tubes

This work presents fundamentals of the laser-induced micro shock waves (LIMS). The shock wave generation mechanism and the subsequent propagation process of the shock in a micro capillary are investigated. In particular, emphasis is put on well-defined and controllable conditions which also offer the opportunity for potential applications in the future. LIMS are induced by an intense 150 fs laser pulse. In succession, they propagate in the strongly confined 2D geometry of a micro tube. Contactless diagnostic tools are applied to investigate the evolution of density and velocity profiles of the shock waves in the tubes. The initial conditions of LIMS are simulated by the hydrocode MULTI-fs.

U. Teubner, Y. Kai, T. Schlegel, W. Garen

Study of MHD Effects in the High-Enthalpy Shock Tunnel Göttingen (HEG) Using a 30 T-Pulsed Magnet System

The interaction between high-enthalpy partially ionized gas flows and magnetic fields, mostly called magnetohydrodynamics (MHD), is regarded as a potential way to manipulate flows. One example is the wall heat-flux mitigation during spacecraft re-entry or entry into an atmosphere. However, the theoretical background and the practical application are still discussed controversially. One way to enhance the knowledge in this field is to utilize advanced computational fluid dynamics (CFD) tools in combination with experimental studies providing suitable validation data. The German Aerospace Center, DLR, has assembled an experiment for the high-enthalpy shock tunnel Göttingen (HEG) to provide data for verification and validation of numerical predictions. A 30 T-pulsed magnet, driven by a 100 kJ capacitor bank, generates the required field. This paper outlines the experimental requirements to obtain magnetohydrodynamic effects in high-enthalpy partially ionized gas flows and the final realization of the experiment. Selected results of experiments using flow stagnation enthalpies of 22 MJ/kg are presented.

J. Martinez Schramm, K. Hannemann

An Electrodynamic Aerobraking Experiment in a Rarefied Arc-Heated Flow

Our previous numerical study (Katsurayama et al. AIAA Paper 2008-4016) has predicted that an insulating boundary in a flow is necessary to activate electrodynamic braking in a rarefied flow: the insulating boundary can prevent the Hall effect from dissipating the current which is necessary for the electrodynamic braking. In order to validate this numerical prediction, the present study measures the total drag on a test model in a rarefied arc flow whose insulating boundary (that is an arc plume boundary) location is variable and compares the measured electrodynamic increases of the total drag with the computed values. As a result, the measured and computed total drags increase by applying the magnetic field, but contrary to the computational prediction, the measured electrodynamic increase of the total drag is insensitive to the insulating boundary location.

H. Katsurayama, N. Fukuda, T. Toyodome, Y. Katoh, K. Tomita, M. Matsui

Blast Wave Propagation Affected by Ground Characteristics

Blast waves are being formed by aerial, surface, or subsurface explosions. The waves propagate in the surrounding media – air and\or ground. In cases of aerial or surface explosion, blast waves are being formed in the ambient air. The waves hit the ground and form a ground shock wave. Ground contraction due to high pressure coming from above followed by rapid expansion may produce a new shock wave, going upward from ground surface. The original wave propagation may be affected as well. Ground movements may also cause fracturing and fragmentation, thus contributing to dust lofting. Suspended dust mitigates aerial wave propagation. All these phenomena, accompanied by ground deformation, make the ground an active agent affecting the aerial shock propagation.In this study we examine the mechanism of ground wave interaction by means of numerical simulations. To this aim we employ a homemade ALE code, named ParaSALE, which includes a variety of equations of state, strength models, and other material-dependent parameters. Dust lofting scheme is based on Mirels’ analysis and assumptions (AIAI J. 22:1582–1589, 1984). Above some threshold friction velocity, vertical momentum dissipation of the horizontal momentum is converted into a vertical mass flow of dust. If the turbulent mass flux is stronger than the gravitational force, the lofted dust particles are coupled to the flow field and being carried by it (Shao, Physics and modeling of wind erosion, Springer, New York, 2008). Changing ground characteristics affects both the ground dynamics and aerial wave. We simulate both sub- and above-surface explosions with various ground specifications. Effects on crater formation and wave propagation will be presented and analyzed.

A. Lipshtat, S. Pistinner

Multiple Reflected Shock Wave in Closed Volume with Granular Screen

Pressure decrease of the shock wave is investigated at reflection from the end of the shock tube channel passing through a sand layer. The influence of the layer location on the pressure pulse extension and on the decrease of the maximal pressure amplitude behind the shock wave is studied. A shock tube was consisted of high-pressure and low-pressure chambers in 72 × 72 mm2 square cross sections. The high-pressure chamber represented a “short” section, 25 cm long, to create the shock wave with the decreasing profile. The impact of a shield made of granulated material on attenuation of the shock wave multiply reflected from walls is investigated at an explosion inside a closed volume. We performed the experiments in the shock tube with a short high-pressure chamber. The low-pressure chamber was filled with air at atmospheric pressure. The flat blast wave with the reducing pressure profile was created. We discover the dependency of the pressure reduction at the reflected wave front on the distance between the protecting shield and the closed end of the shock tube.

O. Mirova, S. V. Golovastov, A. Kotelnikov, V. Golub, T. Bazhenova

Some Aspects of the Numerical Modeling of Shock Wave–Dense Particle Bed Interaction Using Two-Fluid Approach

The work is dedicated to the parametric numerical study of the shock wave with the dense particle bed interaction. The problem is solved using two-fluid approach when both gaseous and dispersed phases are considered to be compressible media nonequilibrium on velocities and pressures. The determinative system of equations has the hyperbolic type and is solved using HLL numerical scheme. The statement of the problem corresponds to the natural experiment. The main features of the process are obtained in the calculations, namely, the formation of the transmitted and reflected waves and the motion of the particle cloud with sharp front edge and smearing trailing edge. The comparison of the amplitudes of the reflected and transmitted waves as well as the dynamics of the cloud motion with the experimental data is carried out. The investigation of the influence of the dispersed phase equation of state parameters and some properties of the numerical methods on the process is carried out.

P. Utkin

To the Complex Approach to the Numerical Investigation of the Shock Wave: Dense Particle Bed Interaction

The problem of planar shock wave–dense particle cloud interaction is solved using two approaches. In the first one, the two-dimensional gas dynamics modeling of the interaction of the planar shock wave with Mach number 1.67 with the set of cylinders is carried out. The original author’s numerical algorithm of the Cartesian grid method is used. The set of cylinders models the dense particles cloud with the volume fraction 0.15. As a result of interaction, the collective reflected and transmitted waves are formed. In the second approach, the one-dimensional system of equations for the description of the dense two-phase flows is solved. Results of one-dimensional modeling are matched with the cross-section averaged pressure distribution from the two-dimensional calculation. The quantitative agreement is achieved. The specific features of the process are discussed. We formulate the idea of complex approach to the investigation of the shock wave–dense particle cloud interaction that is based on the getting of the drag coefficient of the particles bed from the results of the multidimensional calculations and the comparison of those results with the calculation using the two-phase model.

D. Sidorenko, P. Utkin

Numerical Study of Dusty Shock Reflection over a Double Wedge

The shock reflection over a double wedge in dusty gas is numerically investigated in the present paper by the VAS2D (two-dimensional and axisymmetric vectorized adaptive solver) program which solves the compressible two-phase Euler equations with second-order accuracy in space and time. The non-equilibrium effects on the reflection wave configuration are emphasized. The reflection process for a shock wave propagating in dusty gas greatly differs from the pure gas case, and the wave configuration is found to depend on the distance traveled by the incident shock. The reflection wave structures with a short scale are different from that with a large scale. The non-equilibrium effects related to the particle relaxation change the transition criterion and complicate the shock reflection process.

Jingyue Yin, Juchun Ding, Xisheng Luo

Shock and Blast Wave Interaction with Hard Sand Pan

The effect of the passage of blast and shock waves over sand on a hard substrate as well as a hard pan was explored. While the initial entrainment by a blast wave is similar to that by a shock wave, there is a reduction in entrainment after the passage of the negative pressure phase which may reduce the overall estimate of entrained mass. Problems with apparatus and visualization mean that further tests will be required to develop meaningful quantitative data.

R. T. Paton, B. W. Skews

Unsteady Dynamics of Particles Accelerated by a Shock Wave

The dynamics of shock-accelerated nylon microparticles (d p = 4 um) are studied in the post-shock relaxation zone for incident Mach numbers, M s = 1.2, 1.3, 1.4, and 1.5. Particle motion is imaged using a multi-pulse laser and a high-speed camera system. The velocity, acceleration, and the coefficient of drag for an individual particle are estimated based on its recorded trajectory. The absolute shock location is obtained using a shadowgraph system. Results show significant difference from earlier empirical relationships in the variation of C D with respect to particle Reynolds number (Re p).

A. Bordoloi, A. Martinez, K. Prestridge

Shock Focusing Effect upon Interaction of a Shock with Low-Density Dust Cloud

A propagation of Mach 2 and 3 plane shock wave through the air containing cylindrical cloud of low-concentration quartz dust is numerically modeled using Euler’s equations. One-velocity single-temperature model of dust-air mixture is used. A refraction of incident shock and formation and focusing of transversal shocks are described. Two qualitatively different interaction patterns – external and internal – are found to take place for different dust concentration values. A dependence of peak shock focusing point position and relative shock focusing intensity on volume concentration of dust in range from 0.01 to 0.15% is determined. With increase of dust concentration peak focusing point draws near the cloud edge and moves inside the cloud, while focusing intensity non-monotonically rises.

O. Sutyrin, V. Levin, P. Georgievskiy

Shock-Induced Motion of a Spherical Particle Floating in Air

Shock tube experiments were conducted to investigate the shock-induced motion of spherical solid particles and the flow structure around them. In each shot, a spherical particle initially placed on the shock tube floor was tossed into the air and then collided with a planar shock wave with a Mach number of 1.3 when it reached the top of its trajectory almost at rest. The shock-induced motion of the particle and the flow field around it were visualized by the shadowgraph technique coupled with a high-speed video camera. It was found that (1) the separation points and wakes noticeably fluctuated, (2) the shocked particles moved not only in the horizontal (shock propagating) direction but also in the vertical direction, and (3) the drag coefficients obtained from the present experiments were larger than those from the standard drag curve at the same particle Reynolds numbers.

Y. Sakamura, M. Oshima, K. Nakayama, K. Motoyama

Exploring the Capability of a New Shock Tube Facility to Investigate Shock Interaction with Inert Particle Columns

In this paper we present work in progress and preliminary results from experimental studies of shock propagation through particle-laden gas columns. The experiments are conducted in a double-driver shock tube. The tube has a total length of 8.6 m. A setup with a double-driver chamber is chosen, as results clearly demonstrate high degree of repeatability. In order to obtain relatively short shock durations, the total length of the driver section is only 0.12 m. Pressure gauges and high-speed cameras are used to measure the results. A specially designed window section together with high-speed video cameras equipped with telecentric lenses and illuminators allows the shock-particle interaction in directions perpendicular to each other to be captured.

M. G. Omang, K. O. Hauge, J. K. Trulsen

Mitigation of Blast in a Water Mist

The purpose of this work was to study blast mitigation in a water mist and more specifically the effects of the droplet size and of the water mist loading on blast mitigation. A tunnel has been equipped with a water mist fire suppression system. By using this facility, experiments of detonation were carried out in the air and in different water mists. The blast effects were evaluated by means of four pressure gauges placed on the tunnel walls and one pressure gauge placed at the end of the tunnel. The transmission factor of the initial overpressure in the water mist was around 0.8 when four nozzles were used to produce the mist, whatever the size of the droplets. The transmission factor of the initial overpressure was smaller, about 0.6, with eight nozzles generating the mist, either for small or large droplets. The shock wave was delayed by the presence of the mist. The maximum impulse was reduced by about 20% when four nozzles were used to produce the mist, whether the droplets were small or large. The maximum impulse was more reduced with eight nozzles generating the mist, i.e., by about 30% for both droplet sizes.

T. Schunck, M-O. Sturtzer, J. Mory, D. Eckenfels, J-F. Legendre

Shock Wave Propagation Through a Series of Perforated Plates

A simplified analysis can be employed to predict the pressure buildup behind a porous barrier fairly accurately without resorting to numerical modeling. A macroscopic approach is used in which the pressure buildup behind the porous barrier is analyzed in relation to the load inflicted on its front face thus allowing finding the effects of the different parameters of the porous barrier. This method was successfully employed to study the impingement of shock waves and blast waves on stiff silicon carbide foams and more recently on buildings that had enough internal divisions as to be considered as a low porosity medium. In this study, the methodology is employed to study a porous barrier comprised from an array of perforated plates with various porosities to determine the parameters affecting the pressure buildup behind it. Perforated plates were chosen since the geometry of the barriers assembled from the plates is simple enough so it can be exactly defined, and still the shock structure and the developing fields are so complicated that only few studies attempted to deal with similar scenarios in the past. In fact, previous studies were limited to one or two perforated plates. In the experiments presented, 3 mm plates were placed 8 mm apart inside a 32 mm by 32 mm shock tube. The last plate was mounted 10 mm from the end wall. The plates were drilled to accommodate various blockage ratios (defined as blocked to open area ratio) ranging from 50% to 80%. It was found that the volume of air confined inside the porous medium undergoes an adiabatic process, and thus the pressure buildup time at the end wall depends on the volume to the power of the heat capacities ratio.

O. Ram, G. Ben-Dor, O. Sadot

Experimental Investigation of Strong Shock-Heated Gases Interacting with Materials in Powder Form

A novel method is developed in our laboratory to use shock tube for heating the test gases to extremely high temperature and to interact with the materials in the form of fine powder for millisecond time scale. As a case study, we present the results obtained on nitridation of TiO2 compound. Material shock tube (MST) is used to heat Ar and N2 gas mixture to 3750 K–6725 K with reflected shock pressure of about 25–50 bar for about 1–2 ms duration; at these shock conditions, nitrogen gas experiences real gas effect. This nitrogen gas interacts with the rutile TiO2 at the reaction chamber of the MST. The surface morphology, crystal structure, surface composition and electronic structure of the rutile TiO2 sample were examined before and after exposure to shock waves using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).The results obtained from the experimental investigations show the formation of new titanium oxides and oxynitride compounds when exposed to multiple shocks. Formation of new compounds like Ti2O5 and TiN0.74O0.34 is due to noncatalytic reaction occurred during the shock treatment. The result shows that the nitridation of TiO2 is possible in millisecond time scale. MST is an important tool to study catalytic/noncatalytic surface reaction on high-temperature materials near the surface of the re-entry space vehicles.

Jayaram Vishakantaiah

Selective Shock-Refraction Properties in Non-ideal Fluids

The interaction between a low-density spot and a compression shock in non-ideal fluids is studied using the linear interaction theory. Unlike in ideal fluids, the spot can be made to generate powerful sound or extreme shear rates. This is a general property of any substance featuring a local minimum in its sound speed. The selectivity of the refracted field may offer novel strategies to enhance mixing or for sound mitigation in high-speed flows.

E. Touber, N. Alferez

A Numerical Investigation of Oblique Shock Waves in Non-ideal Compressible Fluid Flows

Non-ideal compressible fluid dynamics effects are predicted to occur in flows of fluids characterized by moderate to high molecular complexity, such as heavy hydrocarbons, siloxanes, or perfluorocarbons, by state-of-the-art equation of states. These fluids are of utmost importance in many applications, and non-ideal effects must be taken into account to improve the efficiency of industrial plants (P. Colonna, J. Propuls Power 24:282–294, 2008). This paper is focused on two relevant non-ideal phenomena expected to occur across oblique shock waves for pre-shock states in the close proximity of the liquid-vapor saturation curve. The first one is the possible Mach number increase across the shock wave. This effect is due to the sound speed decrease, for increasing shock strength, along the compressive branch of the shock adiabat. This behavior contrasts with its ideal gas counterpart, for which the post-shock Mach number monotonically decreases with increasing shock strength. For the speed of sound to decrease in a compressive process, the so-called fundamental derivative of gas dynamics Г must be lower than one (P.A. Thompson, Phys. Fluids 14:1843–1849, 1971). The second non-ideal effect is the dependency of the maximum flow deflection angle across an oblique shock on the pre-shock state. Indeed, in the ideal regime, the maximum turning angle depends on the pre-shock Mach number only. To highlight fundamental features, numerical results are presented for a set of exemplary fluid flows. The present findings are expected to be relevant for the design of devices involving supersonic or transonic flow of molecular complex fluids.

G. Gori, D. Vimercati, A. Guardone

Assessment of Real Gas Effects on S-CO2 Flows with Shock Waves

When the CO2 flows through the passages such as compressor or turbine, the state of CO2 changes from S-CO2 to G-CO2 or vice versa. At these conditions, the equation of state (EOS) which predicts one property is failed to calculate the other properties at one temperature and pressure. Hence, it is necessary to assess each EOS available before any computations have been started. In this present work, S-CO2 flow through an overexpanded nozzle is analyzed theoretically and computationally. For the theoretical study, one-dimensional gas dynamics equations were considered along with individual EOS. For the computational study, the 2-D Euler equations were considered. In comparison with flow field along the axis, it is found that consideration of different EOSs has so much deviation in flow properties due to different real gas effects.

Senthilkumar Raman, Heuy Dong Kim

Structure of Shock Waves in Noble Gases Under High-Density Conditions

In the present paper, we show the dependence of the shock structure in a dense, noble gas on each of the three non-dimensional parameters: non-dimensional initial density, non-dimensional initial temperature, and non-dimensional shock velocity. It will also be demonstrated that the length scale, most suitable for measuring the thickness of the shock wave in a dense gas, is the sum of the mean free path (calculated the same way as for a dilute gas) and the diameter of a single gas molecule.

Z. A. Walenta, A. M. Słowicka

Shock Train Structures in Rectangular Ducts

The deceleration of a supersonic flow to subsonic velocity inside a high-speed engine occurs through a series of shock waves, known as a shock train. The generation of such a flow structure is due to the interaction between the shock waves and the boundary layer inside a long duct. This phenomenon is frequently encountered in a variety of internal flow fields where a shock wave interacts with the boundary layer including air-breathing engines, high-speed wind tunnel diffusers, and supersonic compressors and ejectors. The present study investigates the complex SBLI phenomenon encountered in a Mach 2 shock train through numerical analysis.

F. Gnani, H. Zare-Behtash, C. White, K. Kontis

Effect on Shock Train Behaviour of the Addition of a Cavity for Supersonic Intakes

One of the key research areas related to high-speed flight is the ramjet/scramjet propulsion systems. These appear to have the most potential for development into reliable high-speed air-breathing propulsion system. These propulsion systems function by using simple geometries to decelerate the flow through a series of shock waves, a shock train, before entering the combustion chamber. The isolator is an important feature of the propulsion system that is necessary to house this shock train. A significant issue with the operation of ramjet/scramjet engines that this research targets is unstart in isolators. Unstart is the phenomenon that occurs when the isolator experiences an increase in back pressure from the combustion chamber, which itself can be a result of numerous events, resulting in the shock train being expelled out of the propulsion system intake.This research examines the use of a cavity in the wall of the isolator to delay unstart. However the cavity flow must be actively controlled so as to mitigate the negative impact, drag increase, of the cavity addition. Therefore first the cavity flow dynamics must be examined and the active flow control technique, ns-DBD plasma actuators in this case, demonstrated. This paper presents initial work on the baseline facility flow and the impact that the addition of a cavity will have on it.The numerical results presented illustrate that the tunnel and cavity model design performs as expected and that the cavity geometry has little impact on the facility flow field as a whole. The experimental work to follow will validate this study and examine the cavity flow field and its control.

A. Russell, H. Zare-Behtash, K. Kontis

Experiments in Supersonic Gaseous Ejector Using 2D-PIV Technique

Supersonic gaseous ejector is practically a supersonic confined jet, where the primary supersonic jet flows through the confined passage and thereby entrains the secondary flow from the ambient. In this paper, the flow field of the supersonic gaseous ejector is investigated prominently using 2D-PIV measurement technique to study the mixing progression between the primary and the secondary flow at different operating conditions. A rectangular supersonic gaseous ejector (air-air) of low area ratio (AR = 3.7) is used in this study. Two separate supersonic primary flow nozzles of design, Mach number (MPD) 2.0 and 2.5, are considered in this experimentation. Differences between the supersonic free jet and the supersonic ejector or confined jet on the aspects of flow mixing are brought out clearly regarding flow kinematics. Centerline velocity decay, vorticity field, and wall static pressure distribution are used in parallel to explain the mixing progression in the ejector. Influence of the nozzle operating conditions on the gaseous mixing process is found to be prominent. Even a moderately underexpanded primary jet in a low AR supersonic ejector is observed to mix faster due to larger vorticity generation and early interaction of the mixing layer with the confined passage.

S. K. Karthick, Srisha M. V. Rao, Gopalan Jagadeesh, K. P. J. Reddy

Numerical Analysis of Surface Heat Flux in a Forward-Facing Cavity

Passive, semi-passive and active techniques are in active research to tackle the range of heat loads encountered by the hypersonic vehicles. The forward-facing cavity is one of the effective passive techniques explored for hypersonic short-duration vehicles in low-altitude atmospheric conditions. Studies show that the shape of the cavity plays a major role in reducing surface heat flux of the vehicle. To understand comprehensively the surface heat flux characteristics, we have considered the important cavity geometrical parameter, cavity length (L)/cavity diameter (D) ratio, from 0.5 to 5 and compared with and without cavity conditions. The transient simulation results showed that around 10–28% of heat flux reduced over the outer body surface. The variation of pressure and temperature at the cavity base and along the cavity wall for different L/Ds is also discussed.

B. Sudarshan, S. Saravanan

Large Eddy Simulation of Expansion Wave Diffraction

A computational analysis of expansion wave diffraction was conducted using a large eddy simulation solver. The investigation was aimed at resolving particular flow features following a diffracting expansion wave which were previously identified experimentally through shadowgraph imaging but unresolved in the accompanying RANS computational analysis. The features included large-scale turbulent structures within the separation bubble at the apex, a large wake region downstream of the bubble, shear layer instability and vortex shedding. The analysis was made feasible by combining the embedded LES and wall-modelled LES hybrid RANS-LES techniques in ANSYS Fluent. The larger-scale turbulence within the separation bubble was resolved, and vortex shedding was identified in the LES solution. Evidence of the wake region was noted but remained largely unresolved due to the relatively small-scale turbulent motion. An oblique shock, found towards the rear end of the separation bubble, resolved at higher initial diaphragm pressure ratios (PR > 9) in the RANS analysis, was observed from PR = 7.7 in the LES analysis. A strong indication of this shock was seen in the shadowgraph images for PR = 7.7.

Z. Shaikh, B. W. Skews

In-Pipe Aerodynamic Characteristics of a Projectile in Comparison with Free Flight for Transonic Mach Numbers Between 0.5 and 1.5

The transient shock dynamics and drag of a transonic projectile flying through a pipe 3.55 times larger than its diameter are analyzed by means of time-of-flight and pipe wall pressure measurements as well as computational fluid dynamics (CFD). In addition, free-flight drag of the 4.5-mm-pellet-type projectile was also measured in a Mach number range between 0.5 and 1.5, providing a means for comparison against in-pipe data and CFD. For nearly incompressible flow, the presence of the pipe has little influence on the drag. There is a strong increase, however, between Mach 0.3 and 0.8, to a value of about two times the free-flight drag. This is exactly where the nose-to-base pressure ratio of the projectile becomes critical, and henceforth drag can be estimated by supersonic nozzle theory. For even higher Mach numbers, the drag decreases again and finally drops below the free-flight drag. This behavior is explained by five different flow regimes that the in-pipe projectile experiences, as opposed to only two for the free-flying one (subsonic and supersonic, respectively). 2-D axisymmetric CFD simulations agree well with measured values for drag and shock speeds.

R. Hruschka, D. Klatt

Experimental Investigation of Shock Wave Characteristics in Small-Scale Circular Channel

Shock wave propagation through small-scale circular channel is studied using two fast-response pressure transducers. The shock wave is generated by a modified Split-Hopkinson pressure bar shock tube. Pressure profile measured in the channel indicated the sharp increase followed by gradual decrease with fluctuations and several small peaks. Values of peak pressure increase with channel wall temperature, but the shock tube pressure has no significant impact. On the other hand, the intervals between peak pressures decrease with increased shock tube pressure, while the wall temperature has marginal impact.

R. Singh, E. F. Médici, K. Tajiri

Shock Oscillations in a Supersonic Diffuser Flow with Varying Stagnation Pressure

The flow in supersonic wind tunnel diffusers is usually transonic in nature, and the formation of a normal shock just downstream of the diffuser throat region is required for power economy. The behavior of this starting normal shock decides the start or unstarts of a supersonic wind tunnel. The earlier shock oscillation studies were limited to either divergent or constant-area flow situations. In the present work, experimental studies were conducted in a fully transparent Mach 1.7 blowdown tunnel. The experimental investigations included schlieren visualization using a high-speed camera and unsteady pressure measurements. Experiments with increasing and decreasing stagnation pressures indicate a behavior similar to intermittency near bifurcations. Higher stagnation pressure was required in the upstream motion compared to that in the downstream motion. The experiments with different rates of operation are conducted to understand the rate dependency of shock oscillation. The size of the separated flow region determines the shock structure, and the behavior is rate dependent. Hence an optimum starting operation of a wind tunnel can be by increasing the stagnation pressure fast and decreasing it slowly to bring the shock near the diffuser throat.

Jintu K. James, T. M. Muruganandam

Measurement of Shock Wave Attenuation in a Micro-channel

This work presents optical measurements of shock wave propagation in a glass micro-channel. This transparent facility, with a section ranging from 1 mm × 150 μm to 1 mm × 500 μm, exploits a high-speed schlieren videography to visualize the propagation of a shock wave within the micro-channel and to quantify velocity and boundary effects. In this paper, we focus on the Mach waves induced by wall roughness in the supersonic flow behind the wave.

J. Giordano, P. Perrier, L. Meister, M. Brouillette

Surface Jets Produced from an Underwater Shock Wave

Surface effects resulting from the impact of an underwater shock wave have previously mainly been studied as a consequence of underwater chemical or nuclear explosions. Of the many complex features that occur, one is the development of surface jets or plumes. This particular aspect is examined by applying a shock wave impulse to the bottom of a circular disk submerged in a water bath. Different strength shocks are used with different depths of water. It is demonstrated that a wide variety of jets and plumes may be generated.

B. W. Skews, H. Karnovsky

Pressure Sensors for Hostile Environments

We present sensor concepts eventually able to measure pressure pulses traveling in liquid metal, for example, for nuclear fusion applications. Two promising solutions have been tested and validated in water: a fast-response piezoelectric transducer mounted in a custom liquid-cooled housing and a stress bar where mechanical waves produced by the pressure pulse are dynamically measured using strain gauges.

H. Fortier-Topping, M. Brouillette, V. Suponitsky, D. Plant

Visualization of Inception, Propagation, and Collapse Process of Underwater Positive Streamer

Visualization of a whole process of underwater positive primary streamers is difficult because the time scales among inception and propagation of streamers, collapse of streamer gas channels, and formation of residual fine bubbles are different and the spatial scale is a micrometer scale. This study succeeded in successive visualization of the whole process of the streamer with a frame rate of 10 Mfps.

T. Sato, R. Kumagai, T. Nakajima, K. Ohtani, A. Komiya, S. Kanazawa, T. Kaneko

Optimization and Design of a Fully Instrumented Mach 12 Nozzle for the X3 Expansion Tube

This paper describes the optimization and design of a new Mach 12 hypersonic nozzle to be used in the X3 expansion tube. The contoured nozzle has been designed and built to accommodate large-scale models and reproduce constant Mach 12 flows to allow for scramjet testing. The requirements for this nozzle were a core flow of at least 300 mm and exit flow angles below 2°. A new optimization process has been developed, using a parallel Nelder-Mead method, and a new shape has been calculated where CFD analysis indicates the design objectives were successfully met. Off-design performance has been evaluated, and the nozzle has been shown to retain good core flow size, Mach number and low flow divergence for different inflow conditions.

P. Toniato, D. E. Gildfind, P. A. Jacobs, R. G. Morgan

Heat Flux Measurement of Flat Delta Plate Using Phosphor Thermography Technique in Gun Tunnel

Phosphor thermography technique (PTT) is a global optical heat flux measurement method. Phosphor thermography system based on the temperature-sensitivity material has been developed in China Academy of Aerospace Aerodynamics (CAAA), and a brief introduction of PTT is made; the basic parts of this system include phosphor material, calibration systems, UV systems, image acquisition system, and date reductions. CAAA FD-20 gun tunnel is also introduced in this paper. A series of experiments of flat delta plate is performed in FD-20. Global heat flux distribution of the model which shows flow transition is discussed, and a comparison result which is obtained by using traditional heat flux measurement method (thin-film heat transfer sensors) is made; an evaluation on phosphor thermography technique has been made.

Han Shuguang, Jia Guangsen, Bi Zhixian, Wen Shuai

Hypersonic Boundary Layer Tripping to Turbulence on a Conical Body

A low Reynolds number hypersonic flow boundary layer tripping on a conical body is studied. The experiments are performed in a conventional shock tunnel at conditions providing flight realistic combination of Reynolds number and Mach number. It is observed that it is difficult to trip such a flow even with diamond trip heights as much as five times the local boundary layer thickness. Heat flux measurements over the cone indicate that though trip causes local disturbance in the flow field, the boundary layer seems to relaminarize toward the end of the cone.

Tarandeep Singh, K. P. J. Reddy

Hypersonic Flow Computations by Using an Equivalent Gas Model

The aerodynamics of hypersonic vehicles is highly affected by enthalpy or “real gas” effects. The purpose of the current study is to assess the proper formulation of computational fluid dynamics required for simulation of high-enthalpy flows. Under the assumption of chemical and thermal equilibrium, a functional representation has been employed for specific heat at constant pressure, thermal conductivity, and viscosity coefficients for air at 500 to 30,000 K and pressure range of 10−4 to 100 atm. The proposed approach is evaluated using double-cone configuration at hypersonic flow. It is shown that the equivalent gas model is capable of capturing the main features of these flow fields and compares well with experiments.

S. Shitrit, E. Arad

DNS of Hypersonic Ramp Flow on a Supercomputer

The main goal of this paper is to study the hypersonic flow over a compression ramp by highly resolved direct numerical simulations. The results obtained with a grid of 4096 × 512 × 512 points show a very good resolution in the region of the separation shock, the separation bubble, and up to the region of the appearance of Görtler vortices. The development and the detailed structure of Görtler vortices downstream of the reattachment region are shown. The Görtler vortices produce strong spanwise heat transfer variations with significant peak heating. The results for different Reynolds numbers are thoroughly analyzed to show the influence on the vortex-induced spanwise heat flux variations. The comparison of numerical results with experimental data yields a good agreement.

I. Klioutchnikov, S. Cao, H. Olivier

The Role of Three-Dimensional Shock Wave Interaction in the Complex Hypersonic Heating

The phenomena of complex gasdynamic heating exist in the hypersonic interaction region, such as the interaction region of body and wing of hypersonic aircraft. The main mechanism is the interaction of three-dimensional shock waves and boundary layer. This paper explored the role of three-dimensional (3D) shock wave interaction in the complex hypersonic heating based on the theory of 3D shock/shock interaction (SSI). The results show that complex 3D SSI configuration exists in the hypersonic interaction regions in different flight conditions, both regular interaction and irregular interaction. The contact surface induced by the 3D SSI represents the flow jet inclines to the boundary layer of aircraft surface, which always causes the high local heating flux. In the flight condition with a certain attack angle, complex 3D Mach interaction of shock waves in the interaction region of body/wing exists, which induces the complex flow around the wing; the jet bounded by two contact surfaces inclines to the surface of wing and causes the local heating peak, similar to the IV-type heating mechanism in two-dimensional interaction of shock wave and boundary layer.

Chun Wang, Gaoxiang Xiang, Zonglin Jiang, Xudong Li, Zengmin Shi

Numerical Simulation of Effect of Angle of Attack on a Supersonic Parachute System

In the present study, a detailed investigation of unsteady supersonic flows around rigid parachute models is performed by numerically solving three-dimensional compressible Navier-Stokes equations at a freestream Mach number of 1.5. The parachute system employed here consists of a capsule and a canopy. The cases with different capsule angles of attack (α) are simulated. The objective of this study is to examine the effects of capsule angle of attack on the flow fields and investigate ways to suppress the complicated aerodynamic interactions around the parachute models. As a result, it is found that as α is increased, the unsteady pulsation flow mode is weaken, and it almost disappears at α =10 deg.

X. Xue, S. Luo, C. Y. Wen

Experimental Study of High-Altitude Environment Simulation for Space Launch Vehicles

In this work, a high-altitude environment simulation of space launch vehicle has been examined experimentally. One flow condition was used to replicate Mach 6 flight condition for the Korean Space Launch Vehicle (KSLV-II) at an altitude of 65 km. Flow verification was carried out by measuring stagnation pressure, heat flux, and shock standoff distance. Four different configurations of scaled models were used, respectively, to simulate a particular region of the launch vehicle. The models considered examined the shock wave patterns around the launch vehicle, the aerothermodynamic properties on the forebody flow, the aspects of obtaining shock-free technique, and an interaction between nozzle plume and shear layer emanated from the incoming boundary layer of the model.

Sungmin Lee, Gisu Park

Characteristics of Self-Sustained-Shock Pulsation

Shock wave visualization around a circular cylinder with aerospike has been conducted to reveal characteristic of shock pulsation around supersonic parachute. The frequency of shock pulsation has been changed by valuing the ratio of the depth to the diameter, L/D, of the circular model that was valued from zero to two. Pressure history at the bottom of the circular cylinder model was recorded to analyze frequency of the shock pulsation. The characteristic of shock pulsation has strongly been affected by L/D in flow with strong disturbance.

Toshiharu Mizukaki, Kazuhiko Yamada

Free Flight Experiment Investigation of AOA Effect on Cone Boundary Layer Transition at Mach 6

To investigate the angle of attack (AOA) effect of hypersonic boundary layer transition on slightly blunted cone, China Aerodynamics Research and Development Center has conducted a series of ballistic free flight experiments on 5° half angle circular cones. The projectile is 110 mm long with surface roughness between 0.46 μm and 0.77 μm. Six shots were taken under Mach 6 and separated unit Reynolds numbers, and the AOA varied between 0.2° and 7.9°. Results showed that the transition shifted upward to the nose tip on the leeside and afterward to the bottom on the windside within small AOA of less than 3°. When the angle got further increased, the moving direction of the transition on the windside reversed toward the nose tip but will not exceed the leeside in present results with nose tip radius of less than 0.4 mm. The transition Reynolds number without AOA was about 4.7 × 106, and there was a noticeable decrement with AOA, which may relate with both pressure gradient and wall heating difference.

Zonghao Wang, Sen Liu, Jie Huang

Review on Film Cooling in High-Speed Flows

This review presents the state of the art in film cooling applied to high-speed flows. Film cooling is a promising technique to reduce heat transfer and shield a surface that is exposed to high-temperature core stream. The technique applies cold pneumatic injection into a hot core stream, and while the film cooling in gas turbines is generally subsonic, it has also been a success in high-speed environment such as an extension nozzle of liquid rocket engines. The present paper aims to bring together the main results from experiments and numerical simulation on film cooling in high-speed flow. Parameters from not only fluid dynamical conditions but also gas properties and geometric features of injection affect the cooling performance.

K. Fujiwara, R. Sriram, K. Kontis, T. Ideta

Ballistic Range Experiment and Numerical Simulation of Shock Stand-Off Distances Over Spheres in CO2

To provide experimental data for validation of numerical simulations, measurement of shock stand-off distances over spheres in CO2 has been made in the hypervelocity ballistic range of Hypervelocity Aerodynamics Institute, China Aerodynamic Research and Development Center. The models were spheres with a diameter of 10 mm. The flight speeds were between 2.122 km/s and 4.220 km/s, with ambient pressures between 2.42 kPa and 12.3 kPa. The shock stand-off distance was measured using shadowgraph. Results revealed that high-temperature gas effect is more obvious in CO2 than in air, while two-temperature nonequilibrium model can basically reproduce the shock stand-off distances over spheres under present test conditions. The flow over spheres of present test is speculated to be mainly nonequilibrium. The accuracy and capability of two-temperature nonequilibrium model in CO2 may differ with different flow speeds and pressures, which need to be further investigated.

Dongjun Liao, Sen Liu, Jie Huang, Hexiang Jian, Aimin Xie, Zonghao Wang

Prediction of Stagnation-Point Radiative Heating for FIRE II

In the present study, modeling of radiative shock layer for predicting stagnation-point heating environment was conducted for a FIRE II configuration. For the analysis of the one-dimensional flow in thermochemical nonequilibrium, a viscous shock layer method with a two-temperature model was utilized including radiative cooling. To estimate the effect of radiative cooling, the flow and radiation fields were analyzed in a loosely coupled manner. To estimate the radiative heating with the effect of non-Boltzmann state population distributions, SPRADIAN14 was utilized. To improve the accuracy of non-Boltzmann modeling, three new electron impact rate models for atomic N and one for O were developed by adopting the state-of-the-art quantum mechanical results for transitions from low-lying electronic levels. The methodologies were verified by applying them to benchmark problems. It was shown that the results are accurate and physically reliable in comparison with available data. Then, two of the trajectory points of FIRE II were analyzed, and the effects of new electron impact rate models were validated by comparing the results with those from the previous rate model. It was found that most of the discrepancies in the previous rate model from the flight data were resolved by introducing the new models, particularly by the “Frost-Tayal” model.

Sung Min Jo, Gisu Park, Oh Joon Kwon

Characterisation of Curved Axisymmetric Internal Shock Waves

Understanding the shape of curved axisymmetric shock waves in supersonic intake-type conditions allows one to better design for downstream compression and heating requirements. Numerical results were obtained for ring wedge models with varying internal surface curvatures and wedge entry angles at different flow Mach numbers. Experimental results were obtained to validate the numerical method. A general power law fit which describes the shape of continuously curved axisymmetric shock wave segments was determined via curve fitting numerical results. The relationships between the curve fit constants in the general curved shock wave shape equation were shown for the models with a wedge entry angle of α = 4° between Mach 2.9 and 3.6. The curve fit constants were found to be self-similar in nature which promoted the process of characterising them with respect to normalised internal radius of curvature and flow Mach number. This resulted in a proposed empirical model which could predict the shape of the continuously curved axisymmetric shock wave segments within particular justified parameter limitations.

A. A. Filippi, B. W. Skews

Comparative Heat Flux Measurement of a Sharp Cone Between Three Hypersonic Test Facilities at LHD

Comparative heat flux measurements for a sharp cone model were conducted by utilizing a high Reynolds number shock tunnel JF8A, a high-enthalpy shock tunnel JF10, and a large-scale shock tunnel JF12 at the Key Laboratory of High Temperature Gas Dynamics (LHD), Institute of Mechanics, Chinese Academy of Sciences, which were responsible for providing the nonequilibrium or perfect gas flows. Through the assessment of data accuracy and consistency between each facility, we aim to compare the heat transfer data of a sharp cone taken in them under a totally different kind of freestream conditions. A parameter, defined as the product of the Stanton number and the square root of the Reynolds number, was found to be more characteristic for the aerodynamic heating phenomena encountered in hypersonic flight under laminar flows. This parameter can almost eliminate the variability caused by the different flow conditions, and it should be a more preferable parameter for the reduction of the ground experimental data and the extrapolation to flight.

Q. Wang, P. Lu, J. W. Li, S. Wu, J. P. Li, W. Zhao, Z. L. Jiang

Near-Field Pressure Signature over Mach 1.7 Free-Flight Bodies

The shock wave induced by the supersonic flight model and the turbulent flow induced by the free-falling grid were interacted using the time-synchronized launch operating system of the aero-ballistic range. The time-synchronized launch system was successfully done. However, the clear effect of the turbulence on the pressure signature has not been obtained because of the mismatch of the shock Mach number and the induced turbulent Mach number. D-SEND#2, which is similar to the aircraft, scale model was launched with high-precise attitude control by the rectangular-bore core aero-ballistic range, and the near-field pressure around the model was measured. The obtained pressure signature was compared with the numerical simulations, and these pressure signatures agreed well except for the pressure wave originating from the main wing. From these experiments, the experimental capability of the aero-ballistic range was extended.

Y. Aoki, D. Yoshimizu, A. Iwakawa, A. Sasoh

Experimental Study of Radiation Behind Reflected Air Shock Waves

In our laboratory, the characteristics of radiation behind air shock waves have been studied systematically by using a shock tube. In this study, shock waves with different incident shock Mach number were produced under conditions where pressure in low-pressure chamber was kept at constant value and pressure in high-pressure chamber was increased. The radiation behind those reflected shock waves was visualized temporally and spatially by high-speed video camera. In addition, the radiation originated from the chemical species was analyzed by using narrow band-pass filters. Nitrogen and oxygen which are the main components of air were focused; therefore, narrow band-pass filters corresponding and not corresponding to these components were used in order to investigate the amount of radiation intensity. As a result, radiation intensity obtained using the narrow band-pass filters that correspond to the components is stronger than radiation intensity obtained using other filters. Thus, there is a possibility that the radiation intensity obtained using the narrow band-pass filters which correspond to the atomic lines is derived by the atomic lines itself.

S. Yamazaki, A. Harasawa, M. Funatsu

Flow Field for an Accelerating Axisymmetric Body

This study numerically investigates the compressible flow field near an axisymmetric body that is influenced by constant acceleration at 100 g where the motion is straight and level flight. Selected, instantaneous acceleration and deceleration results are compared to steady-state flow at corresponding projectile Mach numbers. The geometries tested were sharp 10° and 30° half-angle cone-cylinders with constant cylindrical aft section. Significant differences in the behavior of the flow field were found for the transonic Mach number range when compared with steady-state results. This was largely due to relative movement of the shock systems and their influence on the near flow field around the projectile. In particular, acceleration was found to delay the complete development of the bow shock and alter the expansion region at the cone-cylinder interface. Deceleration caused all shock structures to propagate upstream relative to the body and influence the nature of the flow field in a different manner compared to acceleration. The flow history concept was evident in both geometries and is demonstrated using simulation results from acceleration cases.

I. Mahomed, H. Roohani, B. W. Skews, I. M. A. Gledhill

Modeling of 3-DOF Launch Dynamics in Transonic and Supersonic Regime Using Navier-Stokes Equation

The modeling of rigid body dynamics including the trajectory estimation of a launch vehicle is essential to investigate the effects of various flow interactions with vehicle for possible instabilities encountered in the transonic and supersonic regime. This work presents a systematic formulation for simulation of the vehicle trajectory under aerodynamic forces, which are calculated by solving the Navier-Stokes equations using the open-source software package SU2. A closed-loop computational framework consisting of computational fluid dynamics (CFD) and kinematic equation solver has been developed. This framework (Fdynam) has been used to estimate typical properties of launch trajectory, viz., Mach number vs. time and dynamic pressure vs. altitude, under the effect of thrust, gravity, and aerodynamic loads. A maximum dynamic pressure of 70 kPa and terminal launch phase Mach number of 4.7 have been estimated for National Launch System (NLS1.5) configuration during powered ascent to an altitude of 30 km.

Anupam Purwar, Gopalan Jagadeesh

Skin Friction Measurement Based on SSLCCs in Hypersonic Wind Tunnel

This paper describes a creative application of global skin friction measurement based on shear-sensitive liquid crystal coatings (SSLCCs) for delta wing in hypersonic wind tunnel. The system of optical skin friction measurement is built, and some wind tunnel experiments are performed in China Academy of Aerospace Aerodynamics (CAAA). Global skin friction distribution of the model which shows complicated flow structures is discussed, and a brief mechanism analysis and an evaluation on optical measurement technique have been made. The experiments prove this method practicable, and it valuably solves the hard problem of skin friction measurement in hypersonic flow condition.

Xing Chen, Bi Zhixian, Wen Shuai, Dapeng Yao, Junjie Pan

Thermo-structural Design of Hypersonic Vehicle Sharp Leading Edges for Thermo-erosive Stability Using Finite Element Modelling

Hypersonic vehicle structural components with sharp geometries, namely, strut, cowl and nose, experience high pressure and heat flux due to flow stagnation. Besides the heat flux and pressure, high-temperature erosive environment is also experienced by such structures. Thus, evaluation of high-temperature wear becomes crucial to design of such sharp structural components. In present work, thermo-structural analysis along with evaluation of damage due to wear-induced mass loss has been carried out by using wall temperature-dependent pressure and heat flux estimated from computational fluid dynamics analysis. Critical design parameters, namely, temperature, stress and mass loss due to erosion, have been estimated considering non-linear material behaviour of ZrB2-SiC-based ultrahigh-temperature ceramic. Multiple temperature-dependent erosion models for ZrB2-SiC have been developed, and maximum mass loss of 74 milligrams has been estimated for ZrB2-SiC strut subjected to heat flux of 6.08 MW/m2 and 753 kPa pressure in Mach 3 flow for 300 seconds duration.

Anupam Purwar

Computational Study on Rigid Disk-Gap-Band Supersonic Parachute Aerodynamics

In Mars, supersonic parachutes have been used as a decelerator at around Mach 2. In order to stabilize the parachute, NASA proposed a supersonic parachute equipped with a gap and a vent, called disk-gap-band (DGB) supersonic parachute. However, it is not fully investigated how its surrounding flow field and its aerodynamics are affected by the gap and the vent (a small ventilation hole at a stagnation point). In this study, a computational study has been carried out on the aerodynamics of rigid-body-modeled parachutes. Results indicate that computed drag coefficient is in good agreement with the experimental data. Moreover, it is observed that reduction of drag per opening area by the vent is greater than that by the gap. Two factors are considered for this reduction: (1) the vortices around the jet from the gap and (2) the vent location at a stagnation point.

K. Takabayashi, K. Fukumoto, K. Kitamura

Numerical Simulation of Laser Ablation Propulsion Performance for Spherical Capsule

The purpose of this research is to study the performance of laser ablation propulsion with a numerical method based on computational fluid dynamics (CFD). We focus on the propulsion performance when pulsed laser beam is irradiated on a 10-mm-diameter spherical model. In this paper, 1.3 mm pulsed laser beam and a so-called donut-mode laser beam were both done to validate a simple numerical method without laser ablation model under 10 kPa – 100 kPa ambient pressure. The flow field quantities were solved with three-dimensional Euler equation by finite volume method. Blast wave energy conversion efficiency η bw and momentum coupling coefficient C m were both investigated by comparing between numerical simulation and experiment. Specifically, a so-called explosion source model is used to simplify laser ablation process and estimate blast wave energy conversion efficiency η bw in this numerical method. Relatively good results of η bw and C m are obtained with this method. Finally, results of donut-mode laser beam simulation are presented about blast wave expansion andC m.

C. Xie, D. T. Tran, K. Mori

Investigation of the Heat Transfer in Hypersonic Flow on Modified Spike-Blunt Bodies

Hypersonic vehicles experience high levels of drag and aerodynamic heating during flight which has to be considered during the vehicle’s development phase. For this purpose, the high-speed community has been studying various techniques to minimize these effects, which in turn leads to longer range, lower fuel consumptions, and safer flight. In the last seven decades, one of the most reliable techniques developed was spikes. A spike mounted on the nose of high-speed vehicles modify the external flow field by pushing the bow shock away and causing flow separation zones ahead of the body where the pressure and heating rates are lower. In this study we have performed experimental and computational investigation of heat transfer over hemispherical blunt body with a modified spike protrusion in front which is termed as “double spike.” Further, we have compared this double spike with the single spike configuration along with the blunt body case.

N. Gopalakrishna, S. Saravanan

Numerical Investigation on the Effects of Air Dissociation upon Hypersonic Projectile in Standard Atmospheric Air

In this paper, the aerodynamic and thermal effects on hypersonic projectile which is launched by ground-based railgun are investigated. Air dissociation effect, which is the typical chemical reaction in hypersonic regime, is focused due to this influence to aerodynamic coefficient and temperature. Around projectile tip, strong dissociation reaction is generated due to high pressure and temperature. Also, there are dissociation region in the back part because of recirculation region. While the effect of dissociation to aerodynamic coefficient is small, surface temperature is affected by dissociation reaction.

Hirotaka Kasahara, Akiko Matsuo

Shockwave Oscillation Under Critical Starting Mach Number in Hypersonic Inlet

The motivation of this paper was to study the characteristics of start-up and the feature of shockwave under low Mach number in hypersonic inlet. The characteristics of flow field and shockwave at the critical starting Mach number (Ma3.8) without back pressure were numerically studied in the hypersonic inlet in which the design condition was Ma6. The results showed that the flow field and shockwave were unstable, and they were under some certain periodic oscillation state at the critical starting Mach number (Ma3.8). The total mass flow rate between inflow and outlet, the mass flow of throat, and the mass average Mach number of outlet all also showed periodic oscillation. Unmatched mass flow that passed through the throat that could not all pass through the exit of isolator was the induced reason of periodic oscillation. The block of the max mass flux flow through the area of throat was the main factor that caused the periodic oscillation of flow field and shockwave. The unmatched mass flux in internal channel leads to periodic “split out” and “swallow in” of “separation bubble” from the internal channel, which formed the periodic oscillation of flow field and shockwave.

Pengfei Xiong, Hanchen Bai, Xiaofei Zhai, Jun Chen, Zhenfeng Wang

Variation in Spanwise Direction of Transonic Buffet on a Three-Dimensional Wing

Transonic buffet is a self-induced oscillation of shock wave appearing at high angles of attack. We simulated the transonic buffet over the NASA-CRM wing with a zonal detached eddy simulation (ZDES). We found that the frequency characteristics of the surface pressure fluctuation are varied in the spanwise direction and are categorized into three patterns. In the inboard region, the buffet exhibits a periodical oscillation with a single dominant frequency equivalent to the 2D wing. At the mid-span of the wing, although the buffet frequency is equal to the inboard, the wave front of shock moves in the spanwise direction. In the outboard, the spectrum exhibits two dominant modes. One is a periodical oscillation similar to the 2D wing. The other is a high-frequency fluctuation propagating in spanwise direction.

Y. Kojima, M. Kameda, A. Hashimoto, T. Aoyama

Critical Condition of Bow-Shock Instability Around Edged Blunt Body

Critical condition of a bow-shock instability was experimentally investigated for a low specific heat ratio flow in a ballistic range with different gas species and Mach numbers. Unstable shock surfaces were observed in front of an edged blunt body by shadowgraph images as predicted in advance by numerical simulations, and a disturbed flow appeared in the downstream even if the flow condition was close to the critical one. A numerically predicted critical curve in a parameter space of specific heat ratio and Mach number indicated that the instability can be found in a low specific heat ratio and high Mach number flow, being consistent with the present experiments. The density ratio of 10.5 across the shock front is similar to the critical curve; therefore, larger one may be an ingredient to make a bow-shock wave unstable.

N. Ohnishi, Y. Inabe, K. Ozawa, K. Ohtani

Experimental Study on Hypersonic Pitch-Up Anomaly in Shock Tunnel

Abnormal pitch-up phenomenon of winged reentry vehicles at hypersonic gliding was experimentally studied in the high-enthalpy free-piston shock tunnel JAXA-HIEST. The novel multicomponent force measurement technique “Free-flight in wind tunnel” was implemented, which involved the test model being completely non-restrained for the duration of the test and thus experiencing free-flight conditions for a period on the order of milliseconds. The test model was a 10%-scaled HYFLEX Japanese lifting body reentry vehicle. Sixteen miniature piezoelectric accelerometers and eight piezo-resistive pressure transducers were instrumented in the model with three onboard miniature data recorders to store measured data. During the test campaign, the model angle of attack was varied from 30° to 50° with elevon (body flap) deflection angle of 0° and 20°. To derive the high-temperature real-gas effect, the comparison was conducted on the aerodynamic coefficients between perfect gas condition and the high-temperature real-gas condition. The following two test conditions were selected: (1) low-enthalpy test flow condition in which no oxygen molecules were dissociated and (2) high-enthalpy test flow condition in which 40% of oxygen molecules were dissociated. The comparison revealed that the lift-drag ratio agreed quite well in both of the above conditions. However, a significant difference of trim angle was detected at a flap deflection of 0°. The high-temperature real-gas effect was believed to be the major cause of the difference.

H. Tanno, T. Komuro, K. Sato, K. Itoh

Pressure Measurements Around an Electric Discharge Produced on a Wedge in a Supersonic Flow

An original mean for the steering of supersonic projectiles is proposed since several years. Now, the deflection of the trajectory of such a projectile by generating electric discharges producing plasma on its surface becomes very realistic facing the experimental results got previously. The present paper deals mainly with academic pressure measurements carried out on a wedge, the transducers being located very near the electrodes of the electric discharge actuator. The experiments are carried out in a shock tunnel at the Mach number of 4.5 under realistic conditions present at 8 km of altitude. The research is motivated by expectations to be confirmed or not about physical effects producing the motion of the projectile under electric discharge actuation. Several series of tests prove that the electric discharge generating plasma produces a local overpressure around the electrodes. This result is in coherence with the motion of a projectile submitted to electric discharges observed in a wind tunnel and a shock tunnel.

P. Gnemmi, C. Rey, B. Sauerwein, M. Bastide

Thermal Spike Conception for Wave Drag Reduction of Blunt Bodies at Different Supersonic Speeds

A computational study of supersonic flow past blunt bodies in the presence of energy deposition localized in very small regions of upstream flow is carried out. The effect of front separation zone formation due to the interaction of a bow shock wave and a shock layer with “thermal spike” (a high-temperature wake downstream of the energy deposition region) is investigated. The universal similarity condition for effective wave drag reduction of bodies due to localized energy deposition and front separation zone formation is determined.

P. Georgievskiy, V. Levin

Experimental Investigations of a Diffuser Start/Unstart Characteristics for Two Stream Supersonic Wind Tunnel

The present paper aims to clarify the starting characteristics of two stream diffusers. Two types of diffusers are examined for a two-stream supersonic wind tunnel: constant area and C-D diffuser. Experiments are conducted at five different secondary Mach numbers (1.8–2.6) by keeping primary at constant Mach number2. High-speed schlieren and pressure measurements are used to understand the performance of the diffuser. This study reveals encouraging results in performance of this tunnel with optimum diffuser geometry. This work also highlights the visualized unsteady complex flow fields with significant boundary layer separation during the transient period for a different Mach number and diffuser conditions. Hysteresis is apparent in a transient process of start/unstart of a tunnel; it is used to decrease the operating starting pressure of the tunnel.

S. Manoj Prabakar, T. M. Muruganandam

Experimental Investigation of Film Cooling Technique over a Blunt Body in Hypersonic Flow

As an alternative to conventional TPS (thermal protection system), film cooling technique has been previously extensively studied. The aim of the current work is to inject new coolants, i.e., mist (atomized water particles) and N2-CO2 mixture, and study the heat transfer variation over the surface of a blunt body in hypersonic flow.

J. L. K. Sindhu, S. Mohammed Ibrahim, K. P. J. Reddy

Wavefront Aberration in a Laser Beam Induced by Supersonic Flow Field Around a Wedge

Aero-optical experiment is conducted in Mach 7 shock tunnel. To investigate the influence of shock wave and boundary layer on the optical wave, 12° wedge model with window on the surface is designed and used. Vibration of the facility is reduced by isolating the test section table from the facility. Also the nozzle shear layer is avoided by installing another wedge structure on the incident laser beam. Diode laser beam with 635 nm wavelength is shot through the flow field, and two-dimensional Shack-Hartmann sensor measured the wavefront of the laser beam. The flow characteristics are acquired by shadowgraph image and pressure measurement. The angle of the laser beam is varied to study the effect of the line of sight. From the measured wavefront, point spread function is calculated to quantify the bore sight error and Strehl ratio. As the line of sight is lowered, bore sight error increased, and Strehl ratio decreased. Thus, lower line of sight is influenced more by the flow.

Sangyoon Lee, Mancheol Jeong, Minwook Chang, In-Seuck Jeung, Hyoung Jin Lee

Boundary Layer Transition Measurements on Sharp and Blunt Cones in the T4 Stalker Tube

The process via which a hypersonic boundary layer transitions from laminar to turbulent flow is important in determining the length of transitional flow regions which is important information for designers of hypersonic vehicles. The effects of bluntness of the leading edge of the hypersonic body on the unsteady processes in the transitional region have not received much attention in the literature. This paper compares the unsteady processes in the transitional region for a slender cone with both a sharp and a blunted tip at hypersonic flow conditions in the T4 Stalker Tube. Fewer, more isolated turbulent spots were observed for the blunted than for the sharp cone when tested at similar or higher Reynolds number conditions.

David J. Mee, Sreekanth Raghunath

Estimation of the Particle Drag Coefficients for Compressible and Rarefied Flows Using PIV and MTV Data

In the present study, the particle drag coefficients in compressible and rarefied flows are estimated experimentally. In the experiments, the particle and gas velocities in an underexpanded jet are measured using PIV and MTV techniques. The drag coefficients are calculated from the equation of the particle motion using the PIV and MTV data. The resulting coefficient is situated in the region where compressibility and rarefaction effects are believed to be remarkable. The results reveal that the estimated drag coefficients do not agree with those calculated from a well-known empirical relation including the both effects, but the data fit to a relation similar to the form of the Stokes drag law. That is to say, the experimental drag coefficient is inversely proportional to the particle Reynolds number although the coefficient has been believed to obey the empirical relation.

T. Handa, S. Koike, K. Imabayashi

RANS Simulation of Over- and Under-expanded Beveled Nozzle Jets Using OpenFOAM

The present study numerically investigates supersonic jet flows issued at M = 1.45 from a beveled nozzle with 60° inclination. Utilizing rhoCentralFoam solver in OpenFOAM, unsteady Reynolds-averaged Navier-Stokes (RANS) simulations were performed with two nozzle pressure ratios (NPRs) of 2.8 and 4, corresponding to over- and under-expanded exit conditions, respectively. The Mach distributions reveal a more organized near-field shock formation for the over-expanded jet with smaller and periodic shock cells, as compared to those of the under-expanded one. Moreover, the jet flows are deflected in opposite directions for the two different NPRs, indicating a strong dependence of jet vectoring on NPR in addition to the bevel angle. Last but not least, reasonably good agreements can be observed for both qualitative and quantitative comparisons between simulation and experimental results, supporting the notion that the compressible rhoCentralFoam solver in OpenFOAM is suitable to model such supersonic jet flows.

B. Zang, U S Vevek, T. H. New

Exploration of Under-Expanded Free and Impinging Supersonic Jet Flows

The impact of jets on a wall remains one of the most effective means allowing a significant increase in local exchanges of heat. These configurations are therefore particularly used in aerothermal systems. The literature reports several studies on the impact of moderately to strongly under-relaxed jets, both from an aeroacoustics and thermal point of view. Nevertheless, the aerothermal behavior and consequently the effects of exchange with the wall remain little known. Moreover, these flows appear to be difficult to simulate from a numerical point of view. We propose here to describe the first part of an experimental study focused on the description of the topology and dynamics of both free and impinged under-expanded jets with the aim to define an accurate database dedicated to the improvement of numerical flow models.

D. Donjat, F. Nicolas, O. Leon, F. Micheli, G. Le Besnerais, F. Champagnat

PIV Studies on the Effect of the Number of Lobes in a Supersonic ESTS Lobed Nozzle

ESTS lobed nozzle is found to be efficient in supersonic jet mixing applications. In this study, the influence of a number of lobes on the aspects of mixing is probed using the 2D-PIV measurements. From the analysis of the obtained 2D velocity field, the kinematics of the lobed nozzle is reported for the first time experimentally. Centerline velocity decay, turbulence intensity, and mass efflux are calculated to compare the influence of a different number of lobes in the lobed nozzle. The conical nozzle is used as the base nozzle for comparison. It is observed that the three-lobed nozzle is efficient in terms of mixing and jet spread. Especially an increment of 70% in the jet spread is observed for three-lobed nozzle. The primary reason for the observed enhancement is due to the higher penetration of the lobe tip into the core flow (by 30% compared with the six-lobed nozzle) which produces larger-scale streamwise vortices than the other cases under consideration.

S. K. Karthick, V. Albin, Srisha M. V. Rao, Gopalan Jagadeesh

Numerical Study of Heat Transfer on Confined Under-Expanded Impinging Jet from Slot into a Plenum

The aerodynamic thermal loads on under-expanded jet from bleed slot into a plenum are obtained at different conditions. It grossly differs from the unconfined impinging jet due to the appearance of left-confined wall. The numerical results show that at low slot angle, heat flux along impinging wall peaks twice due to the stagnation of high enthalpy flow and the shock wave/boundary layer interactions, whereas only one peak occurs at higher slot angle due to the former mechanism. When impingement angle is larger than 50°, the highest thermal loads change a little. As the impingement height increases, the overall aerodynamic thermal loads decrease at the same freestream conditions. Generally, it is the confined wall that makes the flow behind the plate shock supersonic, which allows the SWBLIs to occur.

Tinglong Huang, Lianjie Yue, Xinyu Chang
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