Fluid Mechanics and Fluid Power, Volume 3

The initial part of the given study involves numerical studies on the automotive underhood aero-thermal phenomena with a simple car model and a heat source fixed to it under the hood. As a further extension of the generic case, the second part involves numerical simulation of the same car model with a diffuser for the cooling improvement of the battery pack for HEVs. For cooling the battery pack surface, it is important to channel the flow of air without increasing the aerodynamic drag. Underbody diffuser is designed for this purpose. Thus, a battery pack build into angled surface of a diffuser is used. The diffuser will serve two purposes of reducing aerodynamic drag as well as underhood cooling. The diffuser surface, which in turn affects the battery surface, has more uniform temperatures and smaller hot spots than when there isn't a diffuser.

Impingement of satellite thruster plume on the adjacent surfaces of the satellite generates disturbance torques and heat loads that are undesirable. It is therefore important to configure the spacecraft such that the impingement effects of the thruster plume are minimized. In the present work, Computational Fluid Dynamics (CFD) study of plume expansion in to low pressure environment is carried out, and the impact pressure and heat flux on the flat plate are determined. The simulations are carried out for the reported experimental conditions of plume impingent on a flat plate for various standoff distances of the plate from the nozzle. The Knudsen number distribution shows that the flow remains in continuum in the vicinity of the nozzle and at the impingement region on the plate. The results of the simulation are compared with the measured test data for model validation. Finally, the effect of incorporating temperature jump condition on the impingement heat flux estimation is presented. The CFD model predicts the peak pressure and heat flux within 1.6 and 11.9% of the measured data.

The confinement effect on two recirculation zones (RZ) observed in the coaxial swirling jets is investigated by employing the numerical unsteady Reynolds-averaged Navier–Stokes (URANS) approach. The RZs are classified based on modified Rossby number ( $${\text{Ro}}_{{\text{m}}}$$ Ro m ). A $${\text{Ro}}_{{\text{m}}}$$ Ro m  > 1 case and a $${\text{Ro}}_{{\text{m}}}$$ Ro m  ≅ 0 are considered. The 3D simulations are carried out in ANSYS Fluent 19.2. In particular $${\text{SST}}\, k - \omega$$ SST k - ω , the turbulent model is employed to capture the turbulent flow field. Two confinement ratios CR = 1.81 and 2.7 are used to study the confinement effect. It is observed that the CR = 1.81 produces a significant wall/confinement effect compared to CR = 2.7 evidenced by the enrichment/enhancement of time-mean vorticity, Reynolds stress, and turbulent kinetic energy contour plots. The CR = 2.7 effect is similar to that of unconfined conditions.

Cryopreservation technology is used for the storage of biological substances. The present work shows the effect of cryogenic temperature (230 °K) on graded PDMS scaffold degradation at the different rates of cooling (− 5, − 2 and − 1 °K/min). Different 2D structures of 5 × 5 PDMS scaffolds had been designed by variation of hole distance and hole diameter. Transient analysis of different structures was evaluated for defined rate of cooling by using of fully coupled heat transfer in solid and fluid along with solid mechanics physics. Five different parameters (temperature, stress, displacement gradient, strain tensor and deformation gradient) associated with scaffold degradation were observed in the presence of water at the different region of interest (ROI). The result shows that significant variation had been found in all parameters affecting the scaffold's degradation.

This paper addresses the development of the meshless local Petrov–Galerkin (MLPG) method. Two major drawbacks of the MLPG method are high computational cost and difficulty in the imposition of essential boundary conditions. Moving least squares schemes (MLS) is mostly used in the MLPG method and has these two major drawbacks. New MLS variants, such as improved interpolating moving least squares, MLS with orthogonal basis functions, and modified weight function in the MLS have been explored in the literature. These MLS variants have been successfully employed in the other meshless methods. Each MLS variant resolves one of the two drawbacks of the traditional MLS scheme. The improved MLPG methods based on these new MLS schemes have been developed for the potential flow problem, and their performance has been analysed in this paper. The improved MLPG method based on MLS with orthogonal basis function and modified weight function is proposed in this paper; it is approximately 8% faster than the traditional MLPG with MLS, and it also enables the Kronecker delta property at the same convergence rate and accuracy level of the traditional MLPG method.

The present study uses a characteristic-based off-lattice Boltzmann method with a conjugate heat transfer model to study natural convection inside a square enclosure with a finite-thickness conducting solid vertical wall. A conjugate heat transfer model based on source term formulation is implemented, which considers the effects of thermal inertia for steady and transient conditions. The Prandtl number, Pr, and the Grashof number, Gr, were set to $$0.7$$ 0.7 and $$10^{5}$$ 10 5 , respectively. Other parameters selected are the non-dimensional solid wall thickness ratio, $$w/L = 0, 0.12, 0.2$$ w / L = 0 , 0.12 , 0.2 , and the solid wall to fluid thermal conductivity ratio, $$\xi = 1, 5$$ ξ = 1 , 5 . The inclusion of the solid wall heat conduction has resulted in lower values of the average Nusselt number, $${\text{Nu}}_{{{\text{avg}}}}$$ Nu avg , which emphasizes the importance of conjugate heat transfer study for practical applications. Due to the presence of temperature gradients in the solid wall, the resulting fluid–solid interface temperature distribution is non-uniform, and the flow circulation pattern becomes asymmetric. As the value of $$w/L$$ w / L increases, a reduction in the value of $${\text{Nu}}_{{{\text{avg}}}}$$ Nu avg is observed. Similarly, for small values of $$\xi$$ ξ , the value of $${\text{Nu}}_{{{\text{avg}}}}$$ Nu avg is lower than the maximum values of $$4.082$$ 4.082 observed in the case of isothermal boundary condition.

In the present work, an attempt is made to map the sensitivity of the existing zero pressure gradient (ZPG) turbulent boundary layer (TBL) wall-pressure spectrum models with different TBL parameters, and eventually, with different Reynolds-Averaged Navier–Stokes (RANS) turbulence models, simulated in OpenFOAM and ANSYS Fluent solvers. This statistical study will help future researchers to choose a particular RANS turbulence model vis-à-vis a particular wall-spectrum model to obtain a reasonably accurate wind tunnel result predicting capability. First, the best predicting pressure spectrum models are selected by comparing them with wind tunnel test data. Next, considering the experimental TBL parameters as benchmarks, errors in RANS-produced data are estimated. Furthermore, wall-pressure spectra are calculated following semi-empirical spectrum models using TBL parameter feed obtained from experiments and computational fluid dynamics (CFD) simulations. Finally, sensitivity mapping is performed between spectrum models and the RANS models, with different normalized wall-normal distances from the flat plate ( $$y^{ + }$$ y + ).

The concept of two-phase natural circulation loops (NCL) finds numerous conventional and non-conventional industrial applications due to its passive nature, less cost, and fewer moving parts. However, the dynamics of these systems are complex due to their regenerative feedbacks. Further, the two-phase flow patterns may change in the transient process. Therefore, the developed models should be valid and predictable in those flow patterns. In this connection, two-phase NCL models based on (Homogeneous Equilibrium Mixture Model (HEM) and Drift Flux Model (DFM) are developed using the finite volume method. Flashing phenomena, fluid and wall conduction, and water property subroutine are considered in the model. The models are validated against experimental NCL loops available in the literature. The start-up dynamics of two-phase NCLs are predicted and compared between HEM and DFM models. The drawbacks of HEM and the advantages of DFM are discussed. The changes in flow regimes during the transients are also captured using the models based on available flow regime maps. It is observed that during the transients, the flow regimes change drastically, and DFM predictions are comparatively better than HEM. In the end, the influence of input power, diameter, and height on two-phase NCL dynamics are elucidated using DFM and HEM models.

The phase field method provides a simple mass conserving method for solving two-phase immiscible-incompressible Navier–Stokes Equations. The relative ease in implementing this method compared to other interface reconstruction methods, coupled with its conservativeness and boundedness makes it an attractive alternative. We implement the method in a parallel structured multi-block generalized coordinate finite volume solver using a collocated grid arrangement within the framework of the fractional step method. The discretization uses a second-order central difference method for both the Navier–Stokes and the phase field equations. A TVD-based averaging technique is used for calculating density at cell faces in the pressure correction step to handle high-density ratios. The simulation framework is verified in standard test cases: Zalesak Disk, a droplet in shear flow, Solitary Wave Run-up, Rayleigh Taylor Instability, and the Dam Break Problem. A second-order rate of convergence and excellent phase volume conservation is observed.

Cooling of sensitive electronic equipment in military and space applications is very effective with the help of pulse tube cryocoolers. Out of the available pulse tube cryocoolers, the inline type Inertance Pulse Tube Cryocooler (IPTC) model is widely implemented. In the present work, the effect of pulse tube tapering is examined against the straight pulse tube model using numerical methods. Property variations for solids and fluid are considered for a 2D axis-symmetric model. A User-Defined Function (UDF) is developed to mimic the compressor action having an operating frequency of 30 Hz and pressure oscillation of 11–21 bar. Out of the 3 models considered inward tapering of the pulse tube is proved to reach a temperature of 45 K.

Subcooled flow boiling is an attractive phenomenon to enhance heat transfer from fuel assemblies in nuclear power reactors. Eulerian-Eulerian Two Fluid (EETF) model in conjunction with Wall Heat Flux Partitioning (WHFP) model is found suitable to simulate the physics of subcooled flow boiling. However, these models depend on a large number of closure relations. For high-pressure applications, development and testing of such correlations are still underway, owing to the complexity of various multi-scale processes involved in this mechanism of heat transfer. The developmental nature of these models makes it an attractive option to use open-source codes like OpenFOAM due to the flexibility of incorporating new models and testing them. In the current study, the EETF and WHFP models available in OpenFOAM are evaluated against the extensive experimental data set (pressure: 15–150 bar, mass flux: 400–2000 kg/m2/s, heat flux: 0.38–2 MW/m2) from literature using generally recommended closure relations. It is observed that the model predictions for the overall trends in the cross-section averaged void fraction profiles are reasonable, while some systematic deviations are discussed. This study is expected to serve as a baseline for further research in improving the high-pressure subcooled boiling models and their testing in OpenFOAM.

The potential flow around the square cylinder with rounded corners is investigated by using complex variable approach. The area outside the square geometry with finite corner radius is mapped to the outer region circular geometry using hypotrochoidal transformation. The superposition of complex potential functions for uniform flow, circulatory flow, and vortex flow is employed along with mapping function to investigate various flow parameters around the square cylinder for different corner radius, angle of incidence, and vortex locations around the cylinder. Some of the results attained using present method are compared with the results extracted from ANSYS FLUENT and existing literature for the same geometrical and input flow parameters.

Stalling conditions have the most significant impact on the aerodynamic performance of vertical axis wind turbines. This paper presents the formation of dynamic stall on NACA0012 airfoil using modern numerical technique. The impact of changing the angle of attack on a single-bladed airfoil at a modest Reynolds number is investigated. For the current case, SST-SAS turbulence model was investigated. Flow attachment and separation of flow across the airfoil in the form of vortex formation, propagation is depicted using velocity vectors. The coefficient of lift and drag performance metrics have been also investigated for critical angles of attack and the findings demonstrate good agreement with the experimental data of the literature. The estimated error was reduced significantly using an advanced numerical technique as compared to the error reported in the literature. A slight modification in the geometry of airfoil is also proposed to improve the performance characteristics.

To maintain the shelf life of horticulture products, the product is pre-cooled by forced air pre-cooling technique before the final storage or transportation. Optimization of the ventilation of the packaging systems is essential to improve cooling uniformity. Optimization of the packaging box design depends on vent size, area, and location. The present study is concerned with the location of the vent holes in the pre-cooling of apples. A 3-D CFD model is developed based on the existing package. Numerical simulations are performed to study the pre-cooling process. The location of the vent holes from the vertical edges of the package is varied from 6 to 8 cm. The obtained results indicated that the location of vent holes on the package significantly affects the cooling performance. It is found that vent holes kept at 8 cm away from the vertical edge of the package show better cooling performance for the other two configurations. It is also observed that temperature inhomogeneity reduces by 25.8% without rise in the energy consumption.

Steady state, Reynolds-averaged-Navier-Stokes (RANS) simulations of incompressible flow past NACA 0012, 4412 and 8412 airfoils placed above an impermeable wall are conducted. Ground effects on airfoils of different camber are studied. The effects of varying values of wall distance from trailing edge are studied at a fixed chord-based Reynolds number of $$3 \times 10^{5}$$ 3 × 10 5 and two different values of angle of attack, 0° and 10°. At angle of attack of 0°, lift coefficients are observed to increase for 8412 airfoil (with higher camber) and decrease for 0012 and 4412 airfoils with decreasing wall distance from trailing edge. At angle of attack of 10°, lift coefficients are observed to increase for 8412 airfoil as well as 0012 and 4412 airfoils with decreasing wall distance from trailing edge.

The primary goal of this study project is to learn more about the heating, ventilation, and air conditioning (HVAC) in the office space. Considered are three different air-conditioning arrangements. The simulation programme utilized is ANSYS2021 R1. Accordingly, the computational fluid dynamics (CFD) simulation and analysis for the issue involving a person’s thermal comfort is displayed. The person expects to work in a comfortable setting, yet the stifling air conditions in an indoor office room hinders their productivity. Different boundary requirements have thus been given to the office room for this problem. Utilizing the realizable k-epsilon model, which allows for scalable wall functions, the analysis is carried out. The CFD simulations in an office room area are computed in this study. Comfort conditions achieved by using different air flow velocities are evaluated and analyzed.

This paper is concerned with the prevention of expansion shock given by some upwind schemes. Upwind schemes for the Euler equations of gas dynamics, be it flux vector splitting (FVS) or flux difference splitting (FDS), have many attractive shock-capturing properties. However, some of these schemes are known to give expansion shock, thus violating the so-called entropy condition. It is not very easy to say whether a particular upwind scheme violates the entropy condition, as lack of evidence cannot be taken as a rigorous proof for satisfaction of the condition. For some schemes that are known to violate the entropy condition, a number of entropy fixes based on the flux function have been suggested in the literature. Here we propose a more general method of fixing the problem by controlling numerical dissipation of the schemes.

Liquid metal batteries (LMBs) are potentially attractive option for large-scale energy storage devices at grid scale. We present here the results of numerical simulations performed on a cuboidal LMB geometry using OpenFOAM (OF). We have developed a magnetohydrodynamic (MHD)-based multiphase flow solver ‘epotBInterFoam’ which has MHD equations coupled with the volume of fluid (VOF)-based solver in OF. We study the electro-vortex flow (EVF) in the LMB electrode that creates a jet leading to interfacial distortions at the electrode–electrolyte interface of the LMB. Such interface disruptions can create short circuits in practical LMBs. We consider six cases with each case differing in geometry or boundary conditions. We find that the interface becomes more unstable with increasing electric voltage and decreasing width of the negative current collector. A voltage as small as 0.00764 V can lead to short circuit and is sufficient to disrupt the LMB functioning and make it unsafe for use.

In the present study, convective heat transfer, in a laminar two-dimensional flow of a backward-facing geometry is analyzed. The effect of introduction of an appendage at the edge of the step, to provide an obstruction in the flow and thus to enhance the heat transfer, has been numerically studied. The governing equations are solved in the finite volume method. The flow is considered to be laminar. Air with a Prandtl number of 0.7 is considered as the fluid. The effect of variation of Reynolds number (1 ≤ Re ≤ 1000), on various appendages is analyzed. The heat transfer enhancement is studied by primary recirculation length, average Nusselt number, pressure coefficient and performance evaluation criteria (PEC). The effect of orientation of the appendages has also been studied. The best improvement in heat transfer rate over the backward-facing step is generated by an appendage of length and has a value of YA/S = 0.84. However, PEC and pressure coefficient analysis indicate an appendage of YA/S = 0.33 and 0° is more suitable for increasing the heat transfer for a nominal pressure drop.

With the demand for increased computing precision and a large-scale domain in many computational fluid dynamics (CFD) problems, the computational load on the processor is getting heavier than ever. The graphical processing units (GPU) have proven to be an excellent computing platform for carrying out high precision floating-point computational loads. There is no such direct provisioning for parallelizing code across multiple GPUs using OpenACC, a directive-based programming model. Hence, a hybrid type of programming is required to tackle this problem. In this present work, hybrid type of (CPU + GPU) parallelization of the Poisson solver on multi-GPU was demonstrated using directive-based programming models (OpenMP and OpenACC), which reduced the computational time by 61 × on multi-GPU when compared with a single CPU. We have further analyzed a turbulent 3D lid-driven cavity flow using a direct numerical simulation (DNS) using this multi-GPU solver. The numerical computations and experimental results were quite in agreement.

The growing importance and use of greenhouses have led to various advancements in the design as well as other important factors which need to be studied before constructing one. Greenhouse nowadays is not only used for exotic fruits but also for some vegetables. The objective of this paper is to look out for the most optimum designs of greenhouses using velocity as a parameter, their positioning and the modes of their ventilation have been used to analyze the current forms of greenhouses and their correct orientation of them. The main parameter for evaluation is the velocity which is inside the greenhouse environment. The results in the form of contours are then evaluated to choose the best design suitable.

Design and analysis of a catalytic converter is presented in this paper. The catalytic converter is one of the most important elements that are used for the reduction of automobile exhaust emissions. But in the present work, it is observed that the catalytic converter increases exhaust back pressure. Due to this, volumetric efficiency will decrease and fuel consumption will increase. The main aim of this paper is to investigate the effect of back pressure and velocity by increasing and decreasing the diffusion angles. In this study, different geometries were analysed with variable diffusion angles. The numerical analysis shows that with an increase in the diffusion angle by 7°, the pressure drop is increased by 6.03% in the base model. On the other hand, when diffusion angle is decreased by 7°, then pressure drop is reduced by 9.72% in the base model. When the angle increased by 7°, the velocity increased by 25.04%, and when the angle decreased by 7°, the velocity decreased by 19.44%.

The spent fuel reprocessing under PUREX process that separates Pu and U from fission products is widely used to generate additional amount of energy from nuclear reactors. The plutonium nitrate solution obtained from solvent extraction is converted to plutonium oxide powder through reconversion for the deployment of plutonium-based fuels in the reactor. Plutonium is precipitated as plutonium (IV) oxalate from the nitrate solution using oxalic acid in batch or semi-continuous precipitator, followed by filtration and calcination to obtain plutonium oxide powder. The understanding of precipitation behaviour of plutonium oxalate particles in oxalic + nitric acid medium is essential for the design of continuous precipitator/thickener to increase the throughput and minimize human exposure. Cerium as surrogate to plutonium is often used under harmless conditions for equipment design and process development. In this work, Euler-Euler simulations of solid–liquid disengagement were performed to investigate the detailed hydrodynamic inside a continuous precipitator by varying different parameters such as impeller speed, solid concentration and height of overflow outlets. The predictions through computational fluid dynamics (CFD) simulations is utmost important for the design of continuous precipitator/thickener in Pu reconversion. The developed CFD model will be useful to simulate the cases which are experimentally not feasible.

This numerical study investigated fluid flow behaviour in a horizontal channel partially filled with a metal foam block with various foam lengths. The effect of inlet velocities from 6.5 to 12.5 m/s and different pore densities from 5 to 30 PPI is analyzed. Results show that the location of eddy formation, the magnitude of pressure drop, and friction factor vary with the inlet velocity, foam length, and pore density. Pressure gradient increased with inlet velocity, PPI, and $$\frac{{l_{\text{f}} }}{{l_{{\text{f}},{\text{max}}} }}$$ l f l f , max , with the highest value of approximately 1190 Pa/m for the case of 30 PPI, 12.5 m/s, and $$\frac{{l_{\text{f}} }}{{l_{{\text{f}},{\text{max}}} }}$$ l f l f , max  = 1. The friction factor increased with PPI, $$\frac{{l_{\text{f}} }}{{l_{{\text{f}},{\text{max}}} }}$$ l f l f , max and decreased with inlet velocity with a maximum value of 4.2 for the case of 30 PPI, 6.5 m/s, and $$\frac{{l_{\text{f}} }}{{l_{{\text{f}},{\text{max}}} }}$$ l f l f , max  = 1. Low inlet velocity and high PPI result in more deviation of fluid flow from the bulk flow direction, upstream of the block. There is a tendency for early variation of fluid flow for more extended foam blocks.

In the present research work, the results of numerical investigation for combined natural convection and radiation inside a differentially heated square cavity consisting of horizontal partition are studied. The left wall of the cavity is considered as hot, right wall as the cold wall and the top and bottom walls are considered to be adiabatic. Also, the partition is considered to be adiabatic. The study is done for Rayleigh number 103–106. Air is taken as the working fluid having a Prandtl number of 0.71. The governing equations of fluid flow and heat transfer are solved using finite volume-based method. Discrete ordinate is used as the radiation model. The thickness of the partition for the analysis is considered to be one twentieth of the length of the cavity. The temperature and streamline contours along with the values of convective and radiative Nusselt number shows a significant effect of both convection and radiation in the heat transfer phenomenon. It has been observed from the results of present study that as the length of partition is increased, the NuT also increases as can be seen as when l varied from L/4 to L the NuT increases to 75% and 16% for Ra 103 and 105, respectively. It is also established that when the Ra increases from 103 to 106 the NuT increases to 447% for case 1b.

The current work focuses on the migration of three particles in Poiseuille flow through a slit microchannel. The immersed boundary finite volume methodology based on feedback forcing scheme is used to build the computational model for the analysis of particle migration through slit. Three rigid non-neutrally buoyant cylindrical particles are released from same lateral position in a channel of 20 × 1 dimension. It is observed that the particles travel through the slit and attain equilibrium position at the center of the channel. Further, the influence of slit gap and angle on the equilibrium position and residence time is studied. It is interesting to see that the equilibrium position stays unaffected by the changes in both of the above mentioned parameters. However, the residence time increases with the slit gap. It should be also noted that the migration time is the lowest for a slit angle of π/2.

Radioactive material transport casks [type B(U)/B(M)] are generally employed for the transportation of radioactive material of significant activity. These casks generally employ lead as a shielding material from gamma radiation. Further, the casks must comply with strict standards to withstand the series of tests. One of the tests requires the cask to withstand the fully engulfing fire for about half an hour. As the material lead has a low melting point, it could be a concern from the shielding perspective. This paper presents the results of a 30-min fire test of a radioactive transportation cask exposed to various thermal qualification conditions. To this end, CFD simulations have been carried out with an environment temperature equivalent to that of a hydrocarbon fuel–air fire and a constant 800 °C. It is observed that during the hydrocarbon fuel–air fire test, the lead melted even before the completion of the test. Further, the aspects of Rayleigh convection and its influence on the melting process are discussed in this paper. Additionally, the molten lead is estimated for all cases by the end of the 30-min fire test. Finally, the current investigation details are discussed in comparison with the literature.

The mixing of twin jets on any surface has wider importance in the field of aeronautics and mechanical engineering. The present paper presents the numerical study of mean flow characteristics of twin jets flowing over plane, inclined, and convex surfaces. The obtained results are compared with the results obtained for a jet developing over a plane and a convex surface. The mean flow characteristics considered are mean velocity profiles, decay of maximum velocity, point of intersection, and point of transformation where twin jets to a wall jet profile. Unstructured mesh using a commercial CFD tool with the RSM model is used for the analysis with a second-order advection scheme. The results show good agreement with the existing literature, and the similarity profiles are achieved in the downstream side of flow.

The detailed understanding of thermo-fluid flow is necessary for efficient cooling and operation of data center. This understanding can be obtained by performing a CFD analysis of the data center. Data centers are huge in size, and a detailed CFD analysis requires compute resource, time, and expertise in CFD analysis. In this work, we demonstrate use of OpenFOAM for CFD simulation of an industrial-scale data center. We also discuss about an algorithm and a tool that can create geometry from a 2D layout of an industrial data center. The tool creates mesh and carries out simulation without requiring CFD expertise. Thus, eliminating need of a CFD expert for carrying out CFD analysis on a regular basis ensures optimum operation of a data center. We found that CFD simulation of an industrial-scale data center with our algorithm takes about 2 h of time as compared to the manual simulation which takes about a month of man hour. We have also demonstrated that an OpenFOAM results are as good as Ansys Fluent results on a test data center. The CFD analysis of an industrial-scale data center is fast, accurate, cost-effective, and does not require a CFD expertise.

The nuclear industry has relied on the Nodal Integral Methods (NIMs) for many years as a workhorse. Despite their significant development, the fluid flow community has only a limited level of acceptance for these methods. One considerable drawback with these approaches for solving fluid flow problems is the absence of reliable and effective nonlinear solvers for the algebraic equations generated during the discretization procedure. Recently, some efforts have been made for fluid flow problems to extend the application of NIM for higher nonlinearity by employing the Jacobian-free Newton–Krylov (JFNK) technique, which is an efficient Newton method implementation. In NIM, there is a slight difference between Picard’s and Newton’s implementations; therefore, knowing the required steps for implementing these approaches with NIM is also essential. Preconditioning is usually necessary for both methods for a computationally efficient solution. In the present work, it is realized that the preconditioner developed earlier for Burgers’ equation is more effective in the case of Picard’s method than in Newton’s method. Therefore, the present study compares the implementation process of the Preconditioned Picard and Preconditioned Newton-based approaches within the framework of the NIM. Additionally, spectral analysis and comparisons of nonlinear iterations for both systems are provided to illustrate the convergence of these methods.

The affinities of a biomaterial with cells and substrate were taken into consideration during its designing and development. Numerous disorders like arthritis, cancer, osteoporosis, and atherosclerosis can all be defined by changes in the way cells adhere to one another. In order to reconstruct the complexes in living bodies, researchers might choose to manipulate some aspects of human health based on the properties of specific cells, molecules, or multicellular aggregates. To examine and comprehend biological details like cellular distributions, there are several applications for channels with diameters in the micro- or nano-range. Changes in surface morphology allow for adjustments in the flow profile and the rate of heat transfer into fluid moving through microchannels. This work uses numerical analysis to examine the impact of heat distributions on fluidic flow patterns and potential changes to entropy scaling in the presence of specific micro-topologies over the surface of microchannels. It is possible to analyse the behaviours of cell distributions in micropatterns by using the heterogeneous entropy variation for fluidic molecules brought on by the transfer of provided heat to the working fluid.

The rear wing of a racing car plays a crucial role in generating down force, a key factor for achieving optimal turning speeds. High-speed vehicles, including Formula cars, incorporate various aerodynamic components such as spoilers, rear wings, splitters, and diffusers to enhance overall performance and top speed. However, these components often introduce significant aerodynamic drag. To mitigate the drag effect on straight sections of the track and enhance speed, the Drag Reduction System (DRS) is employed. The DRS implementation leads to a notable speed increase of 15 to 20%. This research focuses on conducting a Computational Fluid Dynamics (CFD) analysis specifically on NACA 2408, 2412, and 2415 airfoils. The objective is to assess the comprehensive aerodynamic impact on vehicle performance, comparing the three distinct airfoil designs (2408, 2412, and 2415). The study evaluates key parameters, including drag coefficient, lift velocity coefficient, contours, down force, and drag force. The findings reveal that the NACA 2415 airfoil outperforms the other two (2408 and 2412) based on the cl/cd (coefficient of lift to the coefficient of drag) ratio. This highlights the superior aerodynamic efficiency of the NACA 2415 airfoil, emphasizing its potential for enhancing overall vehicle performance compared to its counterparts.

The nozzle is a device used at the end of the rocket so as to provide thrust to the rocket to propel. It provides thrust to give momentum and propel any aerospace vehicle. The nozzle design configuration plays a very crucial role in aerospace vehicles. And, it is configured according to the various applications. In the present work, we have attempted CFD investigation on two different shapes so as to compare the performance by estimating the thrust. The two different nozzles which were studied in the present work are (a) the convergent–divergent nozzle and (b) the bell-shaped nozzle. The CFD analysis is carried out using ANSYS 22.0 software to obtain velocity, pressure, temperature, and the flow pattern.

Airflow management is essential for the efficiency of cooling systems in data centers. Numerical approach is useful in the analysis of proposed body force model of data centers either before construction or with existing infrastructure. Perforated plates are significant in several applications because of their abilities to regulate heat and fluid. It is important to address basic problems about how the shape of holes and the void percentage of plates influence fluid flow. The present paper incorporates comparison of different turbulence models for orifice plate simulation and modifications have been made to the tile flow model to account for the flow dynamics through the perforated tile. This analysis is confined to the zone above the floor, where allowable air flow rates at the tile intake is defined. Mathematical model porous jump model and body force model are used to compare the numerical result. The parametric investigation is also done to obtain the design parameters. To check the effect of porosity of perforated plate with respect to the homogeneity of the flow, different porosity 30%, 40%, and 50% of the perforated plate porosities are analyzed.

Gas turbines are usually operated at higher temperatures to enhance their thermal efficiency. At higher operating temperatures, however, the gas turbine blades may fail due to thermal corrosion and cracking. Thus cooling in gas turbines becomes inevitable. The present investigation deals with study of heat transfer and pressure loss characteristics in a two pass channel with variable rib shapes. Four different rib shaped were studied namely square, arched, wavy, and zig-zag ribs. Reynolds Number was varied from 10,000–40,000 and a rib pitch to rib height ratio of 10 was fixed for the present study. Reynolds Averaged Navier Stokes (RANS) Equations were solved numerically in COMSOL Multi-physics 5.4 using the Conjugate Heat Transfer (CHT) module with κ-ω Turbulence model. Thermal performance index (η) for different rib shapes has been numerically evaluated by calculating the normalized Nusselt number ratios and friction factor ratios. It was found that the heat transfer augmenting capability of the ribs relies hugely on the rib shape and the Reynolds Number of the working fluid. At a Reynolds Number of 10,000, wavy ribs outperformed conventional square ribs by 24.96% in terms of normalized Nusselt number ratios and the thermal performance index (ɳ) of the wavy ribs increased by 26.74% when compared to conventional square ribs. Moreover, the frictional losses were minimum is case of wavy ribs.

Most places are prone to fire disasters; in particular, they are a common occurrence in public buildings like hospitals and malls. Modeling the movement of building occupants during such mishaps is a great challenge. The problem is complex as it involves several parameters like smoke movement, time lag for the fire alarms to go off, age and condition of each occupant, number of passages or doors on each floor, the movement of other occupants in the close vicinity, etc. This study tries to analyze the AMRI hospital fire accident reported in 2011 using numerical tools. All the required data for simulations for this event are taken from the reported newspapers and from the reports available on this accident. The building is successfully modeled in a fire evacuation tool, FDS + EVAC. The ability of the model to predict the evacuation of occupants is tested with an assumption of two different stair width sizes. The predicted fractional effective dose (FED) and visibility on each floor with time are reported.

The current study numerically investigates the effect of double fin shape on the constrained melting of PCM in a spherical capsule. The fins are symmetrically spaced from the centre. To ensure that the results are comparable, the base and area of each fin are kept constant across all cases. Straight, trapezoidal converging, stepped, and triangular fin shapes are considered for the analysis. Current numerical results for liquid fraction are being compared with the experimental findings of Fan et al. (Appl Therm Eng 100:1063–1075, 2016) and showed good agreement. Melt fraction, average velocity, and fin effectiveness is being compared for all the cases. Melting time of PCM decreases significantly with the presence of fin. Total time for melting of PCM is nearly the same for stepped and trapezoidal converging fin cases because the surface area to volume ratio (S/V) is similar for both. The triangular fin case has the shortest PCM melting time of 95 min, while the rectangular fin case has the longest melting time of 116 min. The present work could be used for the optimization of LHTES unit integrated with fins in industries.

A three-dimensional numerical study is performed on uniform shear flow past a sphere using Open Source Field Operation and Manipulation (OpenFOAM) at Re = 300. Shear intensity (K) is varied from 0 to 0.125 in such a way that the Re remains fixed equal to 300. Iso-Q surfaces have been plotted to determine the effect of shear intensity on the wake structures. It is found that the flow maintains a plane of symmetry for all values of K. Symmetric plane coincides with the X–Y plane for non-zero values of K. Strength of hairpin shape vortices increases as the value of K varies from 0 to 0.125. Qualitative analysis of the wake oscillations has been carried out with the help of the Hilbert spectrum of a transverse velocity signal in the wake. Marginal Hilbert spectrum has been plotted of a transverse velocity signal to determine the effect of K on vortex shedding frequency.

During a severe accident, the molten nuclear fuel jet breakup in a liquid sodium pool received considerable attention from the Sodium-cooled Fast Reactor (SFR) community. The jet breakup phenomenon assumes importance in the in-vessel cooling of core debris on the core catcher after the accident. The Volume-of-Fluid (VoF)-based solver available in Ansys Fluent with appropriate initial and boundary conditions is used to simulate the jet breakup behavior. To capture the interface accurately and with less computational effort adaptive mesh refinement technique is employed. In the present study molten fuel jet of diameter (D) varying from 1 to 25 mm and with an inlet velocity of 5 m/s is allowed to fall into a column of liquid sodium, the width and height of the sodium column are chosen such that the wall effects are negligible. For cases under investigation, dimensionless breakup length (Lbrk/D) lies between 20 and 35 in the Atomization regime and is close to 35 in the sinuous regime.

Pressure pulsation is inherently present in all centrifugal pumps because of the rotor–stator interaction of impeller and volute. But its higher value may cause trouble in the performance and operation of the centrifugal pump. The experimental method traditionally investigates pressure pulsation, but the advancements in numerical and CFD methods allow us to explore this effect easily. The Tetra/Mixed grid method was used for meshing in ICEM CFD to investigate the transient variation of pressure pulsation. The analysis involves a parametric study in which parameters related to the impact of the cutwater gap (Gap-B) and variable frequency drives on pressure pulsation. The four Gap-B% and four pump speeds were used for analysis of pressure pulsation. Total 8 monitor points were placed in discharge pipes including point at half and quarter wavelength to measure pulsation on the discharge side. From analysis it was observed that Gap-B% had a greater impact on pressure pulsation and an increase in speed also results in significant pulsation. A non-dimensional number was used to compare the results with the experimental method and the results were found to be comparable. Gap-B of 9% and above was found to be optimal since pressure pulsation was less.

Every automotive manufacturer wants to achieve IC engines with maximum efficiency in today's world. To achieve maximum efficiency, engineers try to tweak various components. One such component is the intake manifold. The function of the intake manifold is to provide air to the combustion chamber. The intake manifold is primarily made up of a plenum inlet duct which connects the plenum and runner based on a number of engine cylinders. Researchers have investigated the effect of changing plenum length and runner length, however, there is a lack of literature about the effect of changing runner angle. This paper investigates the effect of changing the runner angle and inlet position on pressure and flow distribution. Six iterations of intake manifold design are investigated using CFD methodology. Parameters such as pressure drop, pressure gradient, and flow distribution are evaluated. The results obtained in CFD analysis show that out of the six designs, the optimal intake manifold design has a runner angle of 120º, and an inlet located offset from the center.

This research focuses on the performance of the 3D unsteady cavitating flow over NACA4412 hydrofoil at angle of attack 40 in the range of super cavitation to non-cavitation zone. The range of cavitation numbers considered from 0.3 to 1.1. The simulation has been carried out in commercial software ANSYS Fluent. Zwart–Gerber–Belamri (ZGB) cavitation model along with Realizable κ–ϵ turbulence model has been utilized for the computation. To analyze the hydrodynamic performance, the lift coefficient, drag coefficient, coefficient of pressure, Strouhal number is computed at various cavitation numbers. It has been found that hydrodynamic performance parameters of hydrofoil are associated with cavitating conditions. For angle of attack 40 moving from super cavitation zone (σ = 0.3) to non-cavitation zone (σ = 1.1), the lift coefficient nonlinearly grows (from 0.2 to 0.8), and cavitation length reduces.

Egypt’s Suez Canal was blocked by a massive cargo ship, which brought global trade to a near-standstill for nearly a week. As a result, a 9% loss in trade value occurred. For six days, one billion USD per day. So, a transport system essential to transport goods through narrow waterways are important. Our study aimed to investigate the NACA0012, and NACA4412 hydrofoils at different values considering attack angles under various velocities and explore the impact of the lift and drag coefficient on the profiles of the hydrofoils hence opting for a more self-propelling model for goods movement.

Geometry-resolved simulations of flow over rough walls are highly expensive due to the associated disparity of geometric scales. Effective or homogenised models are often employed to circumvent this problem. However, existing effective models are aimed mainly at predicting the interface slip velocity on flat interfaces aligned along one of the Cartesian coordinate directions. In a recent work, Sahaj and Sudhakar (Phys Fluids 29, 2017) proposed an effective model in the polar coordinate system and presented results for laminar flows over a rough circular cylinder. Moreover, they introduced two constitutive parameters, named as stress correction factors, for the computation of pressure- and viscous-drag components on rough surfaces. This paper provides additional results of this model and discusses its limitation.

Due to several limitations, it appears that not everyone is now receiving the electricity produced around the world. Furthermore, one of the main ways to generate electricity, fossil fuels, is depleting rapidly. Hence, renewable energy sources are the only alternative solution. One of the best renewable energy sources for producing electricity is hydro energy. Due to their lower payback times and cost economics as independent or isolated energy sources, micro hydropower plants (MHPs) have surged in popularity in recent years. The most often utilized turbines in an MHP are those with low to medium head and medium flow rates. In certain MHPs, pumps are operated in reverse mode, or turbine mode, to lower the overall plant cost. Pumps, however, are not designed to function as turbines. Therefore, there is still potential to enhance the pump in turbine mode with simple, affordable changes. This work aims to numerically evaluate the performance characteristics of a medium-specific speed centrifugal pump operating in turbine mode for one of the minor performance-enhancing back cavity filling modifications. Performance analysis is done for various flow rates at a 1000 rpm shaft speed.

In the present study, the flow physics within an oscillating lid-driven cavity in the presence of a concentric square obstacle is simulated using the in-house developed Lattice Boltzmann Method (LBM) code. The effects of Reynolds number (Re), oscillating frequency of the moving top lid (ω), and size of the square obstacle (Ls*) on the fluid mixing in the enclosed cavity space are discussed. It is noticed that the number of vortices and flow recirculation and mixing inside the cavity rises with an increase of Re and Ls*. However, an increase of ω significantly suppresses the unsteadiness in the cavity region and thereby reduces the fluid mixing.

The muffler plays a crucial role in the automotive transmission system, positioned after the catalytic converter to diminish noise levels. The primary objective is to enhance sound attenuation by effectively combining and nullifying sound waves. Various techniques are employed for this purpose, with thermal acoustics standing out among them. In this method, reducing temperature leads to a corresponding decrease in noise levels. In our current investigation, computational fluid dynamics (CFD) is employed to assess mufflers made of both aluminium and steel. The results demonstrate noteworthy differences, particularly at a specific point (X = 50 mm, representing the inlet tube distance inside the shell). At this juncture, the temperature distribution for aluminium registers at 320 K, whereas steel shows 329 K. This highlights aluminium’s superior heat transfer capabilities compared to steel, especially when varying the inlet tube length of the muffler. Drawing upon published research, it has been established that a decline in temperature contributes to enhanced sound attenuation and a reduction in muffler noise levels. Our study underscores the significance of minimizing noise levels and improving overall noise attenuation in muffler design.

In order to investigate the vortex shedding characteristics of subcritical air flow over a variety of two-dimensional bluff body models, CFD analysis was conducted. In the subcritical regime, flow was simulated for four distinct Reynolds numbers: 45, 250, 800, and 1435 on a circle and a square model both having a hydraulic diameter of 5 mm. In order to examine the flow pattern, shedding nature, and acoustic properties, simulations of both the steady state and transient circumstances were performed. For the Reynolds number of 45, the maximum drag coefficient was demonstrated by both models. Up to a Reynolds number of 250, the drag coefficient drops monotonically, after that it practically stays constant throughout the remaining Reynolds number range. When the Reynolds number is lower (Re = 45), there is no vortex shedding at all for the given two models. Additionally, given the same Reynolds number, the circular geometry with a Strouhal number of 0.175 exhibits the highest shedding frequency. However, for the square model, the Strouhal number reaches its maximum at a slightly higher Reynolds number (Re = 250). The Strouhal number then decreases while Reynolds number continues to rise. The outcome demonstrates that early flow separation induces multiple flow separation sites over the models, which forces a decline in the shedding frequency magnitude.

We present results from numerical simulation of two-dimensional tube convection: natural convection in a vertical tube with an imposed unstable density gradient. Simulations are performed in OpenFOAM, an open-source Finite Volume-based toolbox. The flow is characterized by gradient Rayleigh number $${\text{Ra}}_{g}$$ Ra g which is varied approximately from the onset of convection $${\text{Ra}}_{g} \sim 10^{3}$$ Ra g ∼ 10 3 across four decades to $${\text{Ra}}_{g} \sim 10^{7}$$ Ra g ∼ 10 7 , for a fixed Prandtl number $${\text{Pr}} = 1$$ Pr = 1 . We see that the flowfield is characterized by vertically stacked, counter-rotating eddies or rolls that scale with the diameter of the tube. We show that the average temperature profile in the tube is linear with modulations due to the rolls and that the mixing length model gives a good estimate for fluctuations of the velocities. Evidences for existence of at least three regimes were observed for the scaling relations for Nusselt number, and at high enough Rayleigh numbers, $${\text{Nu}}$$ Nu scaling in 2D tube convection shows trend similar to the $$1/2$$ 1 / 2 power scaling observed in 3D DNS and experiments.

The vortex tube is a device which bifurcates the compressed gas into the cold and hot stream and is used as a flow separator. The shape of the hot outlet throttle influences the quality of cold outlet fluid in terms of temperature. This investigation focuses on the optimization of vortex tubes with three different models for throttle valves, namely conical, square, and truncated. ANSYS FLUENT software has been used to simulate flow, considering air as a working fluid for a steady-state, three-dimensional, axisymmetric, counter flow vortex tube. The standard k-ε turbulent model has been considered for the flow simulation. The effect of the shape of the control valve, intake pressure on temperature, and velocity flow has been studied. The truncated shape control valve shows a promising result for thermal performance enhancement among all the geometries considered. The coefficient of performance (COP) of a truncated control valve is highest compared to other models. The computational result of the present study has been validated with experimental data.

Developments in space technology have demanded high-performance altitude compensating nozzles for long interplanetary missions and reusable launch vehicles. An improved rocket nozzle that can be used as an altitude compensating nozzle is the Conical Plug Aerospike Nozzle. In this study, a coolant is injected in the nozzle’s throat region by altering the shape of the conical plug nozzle. On a two-dimensional axisymmetric model of a Conical Plug Aerospike Nozzle with secondary fluid injection at the throat area, hot flow is numerically simulated. The shear stress transport k-ω turbulence model is used to solve Reynolds-averaged Navier–Stokes equations. With different secondary fluid mass flow rates, it is possible to calculate the temperature distribution on the nozzle wall and the cooling efficiency of the coolant on the nozzle wall. According to the study, utilizing LH2 film cooling in a Conical Plug Aerospike Nozzle is significant and crucial. The study also shows a reduction of specific impulse with increasing coolant flow rate.

When an object passes through a stationary fluid or fluid passes around an object, a resistive force acts on the object called drag. In most of the situations, this drag force is undesirable and needs to be decreased even if it is not possible to eliminate it entirely. Drag forces predominantly occur on bluff bodies. It has been found that the interaction of vortices leads to an increase in pressure drag, which is the largest contributor of drag acting on a bluff body like cylinder. This problem is commonly encountered in engineering applications like windmill towers, underwater bridge columns, offshore oil rig structures, transmission towers. Therefore, the objective of this research is to study the variation of drag force acting on a cylinder. This is possible by attaching splitter plates of varying lengths both upstream and downstream to the flow and parallel to the cylinder. It is found that attaching a splitter plate upstream and downstream reduces the drag by 19.03%

A computational study is performed for laminar 2D simple harmonic cross-flow behind a circular cylinder with cylinder oscillating at an angle α = 90°.The Navier–Stokes equation was used to perform the simulation, and the findings were analyzed for Reynolds no = 500 and 1000 with a constant oscillation amplitude of A/D = 0.02. Research focused on a region of frequencies of oscillation close to a stationary cylinder’s natural shedding frequency. The investigation was done into how the cylinder vibration affected the parameters like wake patterns, phase planes, lift and drag forces, etc. The current computational modeling further establishes the “lock-in” bounds or the synchronization regime. The predicted lock-on range, force amplifications, and vortex-shedding modes exhibit great consistency with earlier experimental and numerical analyses.

Artificial compressibility method (ACM) in its various forms is widely used in numerical simulations of incompressible flows. Unlike the conventional methods, solving a pressure Poisson equation is not required in ACMs, making them computationally less expensive. The classical ACM is confined only to steady-state problems, and the extension to unsteady problems requires dual time-stepping. Apart from marching in actual time, additional inner iteration in pseudo-time is necessary for the dual time-stepping ACM, reducing their computational speed. Recent developments in artificial compressibility methods point towards single time-stepping versions such as entropically damped artificial compressibility (EDAC), general pressure equation (GPE). These algorithms neither involve numerically solving the pressure Poisson equation nor dual time-stepping and hence are computationally efficient. In this work, we developed an incompressible flow solver based on GPE and performed simulations with a few test cases. The unsteady test case of laminar Taylor–Green vortex problem indicates second-order convergence in both velocity and pressure, and the maximum error obtained is of the order of 10−4 for a grid of 64 × 64 at t = 1.0 s. The steady-state cases of laminar flow over flat plate and flow over backward facing step also show excellent agreement with the results reported in the literature.

As the computational fluid mechanics community is advancing rapidly, the need to assimilate and compress the high-fidelity data is increasing simultaneously. Modal decomposition techniques like proper orthogonal decomposition and dynamic mode decomposition are widely used to capture important features (modes) of the flow field to facilitate reduced-order modeling. The frequency-domain equivalent of POD known as spectral proper orthogonal decomposition (SPOD) is currently emerging as a competitive alternative to these techniques. The present work analyzes the efficacy of SPOD compared to POD and DMD in obtaining effective latent space representations that enable accurate low-rank flow field reconstructions of unsteady flows. Suitability and shortcomings of the methods are highlighted for a canonical case of unsteady flow across a stationary cylinder at a Reynolds number of 100, based on the error metrics for low-rank reconstructions. It was observed that first two SPOD modes alone have constituted more than 90% of the energy in the flow. With just four SPOD modes, the flow field was reconstructed with less than 1% error, while it took six modes of POD and DMD to achieve the same accuracy.

A serpentine nozzle directs the jet engine exhaust through bends, to improve flow characteristics and reduce thermal signature, incurring a slight thrust penalty. This property of serpentine nozzles is beneficial for military aircraft operating in hostile airspace, as it improves stealth characteristics. The present work aims to develop a serpentine nozzle model and simulate the flow characteristics using a computational tool. The computational model has been validated against literature data. Four different inlet and outlet geometries have been investigated at Mach 0.9 at 2000 m AMSL. The effect of changing these geometrical parameters on pressure contours and velocities has been analyzed. Based on this study, a cambered rectangular inlet serpentine nozzle is optimal for the target application. Computational results indicate that, for serpentine nozzles, increasing the exhaust velocity after a certain threshold, based on nozzle geometry, leads to unfavorable pressure characteristics. Furthermore, reducing the exit area 0.5 times when compared to the inlet area allows for the best possible expansion characteristics.

Predominant solvers for fluid dynamics simulations rely on second-order discretization using finite volume or finite difference schemes. These methods are robust and reliable for steady flows but suffer in simulating turbulent, unsteady flows for which second-order discretization is insufficient. There is growing interest in higher-order schemes for simulating such flows. One such novel high-order scheme is the Direct Flux Reconstruction (DFR). DFR predicates solving the strong form of the governing equation. Using the in-house solver developed using the DFR approach, validated using Sod’s shock tube case, we solve problems involving complex flow structures. These include shock–vortex interaction, Rayleigh–Taylor instability, and Kelvin–Helmholtz instability.