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2024 | Book

Fluid Mechanics and Fluid Power, Volume 4

Select Proceedings of FMFP 2022

Editors: Krishna Mohan Singh, Sushanta Dutta, Sudhakar Subudhi, Nikhil Kumar Singh

Publisher: Springer Nature Singapore

Book Series : Lecture Notes in Mechanical Engineering


About this book

This book comprises select peer-reviewed proceedings of the 9th International and 49th National Conference on Fluid Mechanics and Fluid Power (FMFP 2022). This book brings together scientific ideas and engineering solutions put forth by researchers and practitioners from academia and industry in the important and ubiquitous field of fluid mechanics. The contents of this book focus on fundamental issues and perspective in fluid mechanics, measurement techniques in fluid mechanics, computational fluid and gas dynamics, instability, transition and turbulence, fluid-structure interaction, multiphase flows, microfluidics, bio-inspired fluid mechanics, aerodynamics, turbomachinery, propulsion and power and other miscellaneous topics in the broad domain of fluid mechanics. This book is a useful reference to researchers and professionals working in the broad field of mechanics.

Table of Contents



Numerical Analysis on the Effect of Aspect Ratio in a Diesel Injector Using Diesel and Diesel–Ethanol Blend

In direct injection diesel engines, spray optimization greatly enhances efficiency and low emissions combustion. The flow inside an injector impacts the process of spray, combustion, and exhaust. The nozzle shape and spray determine the atomization and the outlet engine emissions. The results were obtained for spray characteristics of diesel and ethanol–diesel blend in a nozzle injector with aspect ratios varying from 1, 1.2, 1.4, and 1.6. Parameters, such as spray penetration length, spray angle, and spray characteristics including the Sauter mean diameter (SMD), the De Brouckere diameter, the mean diameter and volume, and particle velocity, were investigated and revealed a strong dependence on modifications in the aspect ratio of the nozzle orifice. Simulation of atomization model was carried out and compared using discrete phase model (DPM) using computational fluid dynamics (CFD) modeling. Additionally, validation from the experiment finding results is also provided. Elliptical C was observed to have a minimum SMD up to 28.04% and a minimum De Brouckere diameter up to 28.63%. Ethanol–diesel blend showed best spray parameters when considering the macroscopic spray properties and the drop size distribution. Moreover, under non-evaporative conditions, the tested fuel ethanol–diesel Blend exhibited better spray characteristics and better cavitation phenomenon of 12.13% at higher aspect ratios than at lower ones. In addition, elliptical nozzle spray had a higher spray cone angle than circular nozzle spray.

Aiswarya A. Satheesan, Nikhil Prasad, Nevin Nelson, S. Niranjan, Anjan R. Nair
Numerical Simulation of Gasification and Plasma Pyrolysis Process for Lignite Coal: A Comparative Study

Computational fluid dynamics is a special tool for modeling thermochemical processes for process parameter optimization. The present study is a comparative study of the gasification and plasma pyrolysis process of lignite coal. Three temperatures (1023, 1123, 1223 K) are selected for the gasification process and a similar is done for the plasma pyrolysis (1223, 1323, 1423 K). The obtained results are compared with the experiment literature available. The RMSE approach was used for checking the accuracy of the model. The accuracy was observed to be appreciable. The composition of the syngas is compared for all the cases. It was observed that the concentration of hydrogen and carbon monoxide is found to be rich in plasma pyrolysis with an average of 43.4% as compared to 13.5% for gasification. The plasma pyrolysis process offered better results compared to the gasification process as it offered a higher H2/CO ratio and (H2 + CO) factor. The CO/CO2 ratio also increased for the plasma pyrolysis process with an increase in temperature.

Sidhartha Sondh, Darshit S. Upadhyay, Sanjay Patel, Rajesh N. Patel
Availability Analysis of Diesel-Powered CI Engines with Single and Multiple Injection Strategies

Injection timing heavily influences the diesel engine performance and emissions. The present study utilizes a various injection strategies such as single injection, 30° BTDC and 50° pilot injection, paired pilot injection, and split injection on the performance and emissions. There are two conditions for a single pilot injection: the first is a 20% pilot injection at 30° BTDC, and the second is a 20% pilot injection at 50° BTDC. A twin injection approach uses a pilot of 5% at 50° BTDC and another 15% at 30° BTDC. Performance metrics like BTE, BSFC, and IMEP are determined at a compression ratio of 18:1 for 1000 RPM. The split injection condition produces a lower NOx, CO, and UHC emission. The pilot operation at 50° produces more CO and NOx emissions. Applying the second law of thermodynamics analysis to the CI engine, exergetic efficiency is assessed for various injection strategies, with split injection exhibiting the most optimal engine performance along with controlled emissions.

Ketan V. Warghat, Aditya Tiwari, B. Yogesh, G. M. Nayak, B. Saravanan, Pankaj S. Kolhe
Change in Vortex Breakdown Mode and It’s Influence on Flame Shape of a Co/counter Concentric Swirling Streams

The present study experimentally investigates the flow field of co/counter-swirling stream under non-reacting and reacting conditions by varying the momentum ratio (Mratio). We utilized two-dimensional particle image velocimetry (2D-PIV) to examine the flow field. For non-reacting cases, co-swirl shows slender recirculation zone (RZ) at low Mratio. The volume of RZ increases slowly till Mratio = 1.1. However, a drastic change in flow field is observed after Mratio = 1.1. In comparison, the counter-swirl configuration has a small ellipsoidal RZ at low Mratio. Similar to co-swirl, a drastic change in flow topology occurs after Mratio = 1.7. This change in flame topology indicates the change in breakdown mode. PIV images indicate two types of breakdowns: bubble (BVB) and conical (CVB) vortex breakdown. This breakdown modes can be observed in reacting cases also. It is observed that the flame shape strongly depends on breakdown mode. The present study unravels few interesting features of the flow field of co/counter-swirling streams.

Atanu Dolai, Prasad Boggavarapu, R. V. Ravikrishna
Entrained Dust Combustion in Pre-Heated Air

In many practical applications, such as in blast furnaces and boilers, pulverized coal is used as a reducing agent and energy source. This chapter presents the predicted characteristics of naturally entrained coal dust flames in a sudden expansion region. Further, it also investigates the effect of particle size and equivalence ratio on the flame dynamics. Commercially available ANSYS Fluent has been used for the numerical simulations. Discrete phase modelling is used for sub-bituminous coal particles tracking. Variable thermo-physical properties are employed. A skeletal chemical kinetic mechanism for methane consisting of 25 species and 121 reactions are used. A User Defined Function (UDF) is used to include the radiation due to species and soot particles. For a given coal flow rate, mass flow rate of air is varied to maintain the required global equivalence ratio at a constant temperature of 1273 K. Particle size distribution (1–25 and 53–63 µm) and equivalence ratio (0.65–0.95) are varied. Steady-state governing equations are solved till convergence. The flame dynamics is investigated through the contours of temperature, devolatilization zones, velocity vectors, mass fraction distribution of important species soot formation and reduction.

Mohd. Tousif, A. Harish, V. Raghavan
An Experimental Investigation into the GDI Spray Characteristics of Ethanol and Lemon Peel Oil

The fuel injection phenomenon significantly influences engine performance and emissions in a Gasoline Direct Injection (GDI) engine. Before using biofuel in a GDI engine, it is critical to understand its spray structure and combustion quality. The current study seeks to deepen the understanding of the spray behaviour of Lemon Peel Oil (LPO) and ethanol in a controlled environment under different pressure, temperature, and engine-like conditions. The thermophysical properties of the fuels help to comprehend the spray characteristics. The liquid spray morphology of fuels is captured using a standard Mie-scattering technique, and the spray penetration length is compared to the baseline fuel isooctane. The constant volume spray study revealed that the Isooctane has the shortest penetration. The higher boiling point of LPO allows for a longer spray tip penetration. Besides, ethanol has a longer penetration than Isooctane despite its low boiling point. Spray collapsing is observed at 1 bar chamber pressure and 453 K temperature due to flash boiling, which reduced the overall spray cone angle, resulting in greater LPO and ethanol penetration, where Isooctane behaves differently in this chamber condition.

G. M. Nayak, B. Abinash, B. Yogesh, V. W. Ketan, P. S. Kolhe, B. Saravanan
Numerical and Experimental Performance Comparison of a Typical Swirl Co-Axial Injector for a Cryogenic Combustor

A swirl co-axial injector is designed, fabricated and tested for a cryogenic combustor using liquid oxygen and gaseous hydrogen. Performance of this injector arrived at through experimental and numerical studies are compared in terms of chamber pressure. The numerical model developed for this injector and combustor is based on a Eulerian–Eulerian framework. It considers the two-phase flow of liquid oxygen and gaseous hydrogen with the assumption of local mechanical and thermal equilibrium, but with a local finite evaporation rate. Chemical reaction of gaseous oxygen and hydrogen is modelled with a modified eddy dissipation concept combustion model. It is found that the chamber pressures calculated by this model matches reasonably well with the test results. The steady-state chamber pressures obtained are 38 bar and 40 bar for experimental and numerical studies, respectively. Further, the numerical results are analysed to understand the flow field characteristics, such as evaporation and mixing, in the tested injector. It is found that the evaporation of the liquid oxygen is complete well within the first quarter and the combustion is almost complete in the three quarters, respectively, of the injector length.

R. Sujithkumar, K. Chenthil Kumar, K. R. Anil Kumar, T. Jayachandran, Kowsik Bodi
Analytical Modelling of Effect of Steam Dilution on Hydrogen Combustion and Application to a Typical Nuclear Reactor Containment

During postulated accident sequences in water-cooled nuclear reactors, steam and hydrogen may be released from the core and form a flammable mixture in the surrounding containment structure. Combustion of such mixtures and the subsequent pressure rise are an imminent threat for reactor containment integrity. Methods for evaluating combustion pressure rise are important for determining the design safety margins in such scenarios. Typically, combustion calculations are based on NS equations and CFD modelling, which are complex and time-consuming. A simpler and much faster approach is to use thermodynamic analysis to compute the final state after combustion for a given initial state. In the present work, thermodynamic modelling based on free energy minimization is presented. Predictions from the thermodynamic model have first been validated with published experimental data for binary hydrogen–air mixture. Then, parametric studies have been carried to compute combustion pressure rise in ternary mixture of hydrogen–steam–air as it represents more realistic mixture during accident. Finally, the model has been applied to a typical nuclear reactor containment to determine design safety margin as well as margin with respect to functional and structural failure of the containment.

Aditya Karanam, Vishnu Verma, J. Chattopadhyay
Thermal Performance of a Single-Layer Porous Radiant Burner with Biogas as Fuel: A Numerical Study

Raw biogas has the ability to minimise waste and greenhouse gas emissions while also helping to meet the world's insatiable energy needs. In this chapter, a circular Porous Radiant Burner (PRB) consisting of silicon carbide (SiC) foam is examined for its ability to substitute raw biogas. Raw biogas mixtures were examined on PRB using ANSYS 19 at firing rates ranging from 1 to 2 kW, and stable combustion was noted over an equivalence ratio range of 0.7–0.95. The increase in fire rate and equivalence ratio increased surface temperature, whereas radiation efficiency increased primarily as an outcome of the increase in equivalence ratio. Within the range of fire rates of 1–2 kW and equivalency ratio of 0.7–0.95, the PRB functions steadily with radiation efficiency of 12.4–37.5%. Furthermore, the newly developed PRB delivers more radiation efficiency for raw biogas than prior systems used in submerged mode.

Ayush Painuly, Niraj K. Mishra
Numerical Validation and Benchmarking of Hydrogen Flame Propagation in a Vertical Acceleration Tube Experimental Facility

During severe accident in a water-cooled nuclear power plant, hydrogen can be generated, leading to risks of possible hydrogen combustion and may threaten containment integrity. In this context, it is important to know the flame speed in a combustible mixture containing hydrogen. The ENACCEF test setup is a vertical acceleration tube with periodic obstacles and a dome of large volume at the top. It is a uniquely designed setup to study flame propagation under severe accident conditions in containment atmosphere. In this work, numerical validation has been carried out for one of the tests conducted at the ENACCEF facility using experimental data available in the open literature. A mechanistic combustion modelling framework especially suitable to fast flame propagation has been evolved and implemented using OpenFOAM. It has been observed that the numerical simulations are able to accurately capture a gamut of observed combustion phenomena like slow deflagrations, flame–turbulence interaction and fast flame acceleration. Moreover, benchmarking with numerical results obtained from other research groups suggests that the present results are more in line with the experimental data. The combined validation and benchmarking studies thus affirm the high fidelity of the adopted modelling approach and its numerical implementation with OpenFOAM.

Aditya Karanam, Vishnu Verma, J. Chattopadhyay
Detailed Chemical Kinetics Mechanism for Condensed Phase Decomposition of Ammonium Perchlorate

The current study aims to improve the understanding of the complex thermal decomposition mechanism of Ammonium Perchlorate (AP-NH4ClO4). The absence of detailed reaction mechanisms for AP with accurate rate kinetics data in the condensed phase is the main challenge of thermal decomposition and combustion modelling. In the present study, AP-condensed phase elementary reactions were investigated using Ab-initio molecular modelling, in which the polarizable continuum model using integral equation formalism variant (IEFPCM) was used to account for the condensed phase and transition state theory calculations are used for calculating kinetic parameters of the reactions. Gas-phase species evolution profiles were obtained from fast pyrolysis experiments conducted isothermally at three temperatures (420, 440, and 460 °C) at 10 bar gauge pressure. The same are used to validate the reaction mechanism. To simulate the fast pyrolysis experiments, computational model based on mass and species conservation in the condensed phase and gas phase control volumes was developed. The predicted gas phase mole fraction profiles of the decomposition products agree well with the experimental results, indicating that the proposed reaction mechanism captures the liquid phase decomposition of AP.

Jay Patel, Prathamesh Phadke, Rohit Sehrawat, Arvind Kumar, Arindrajit Chowdhury, Neeraj Kumbhakarna
Onset of Thermoacoustic Oscillations in an Annular Combustor with Flames Stabilized by Circular Discs

This chapter examines the onset of thermoacoustic oscillations in an annular combustor. The combustor consists of 12 burners with flames stabilized in the flow path using circular discs. The premixed fuel and air are used in the present investigation to scrutinize the observed thermoacoustic oscillations. The acoustic pressure fluctuations acquired in this combustor exhibit two dominant peaks. These peaks occur at 664 and 331 Hz, associated with the first azimuthal-first longitudinal (1A-1L) and first longitudinal acoustic modes, respectively. The combustor dynamics are examined by keeping the fuel flow rate constant with varying the air flow rate. The combustor exhibits non-monotonic variation in acoustic pressure amplitude, with intermediate air flow rates showing relatively large amplitude acoustic pressure fluctuations. Further, we observed a difference in amplitude envelope between the increasing and decreasing airflow rates, illustrating the occurrence of subcritical bifurcation. In addition, the phase space, first return map and recurrence plots are used to characterize the transition from relatively low amplitude to large amplitude acoustic pressure fluctuations.

Balasundaram Mohan, Sathesh Mariappan
Development of Advanced Fuel Injector Concepts for Compact Lean-Burn Gas-Turbine Combustors

The present work investigates the aerodynamics and atomization characteristics of a lean burn fuel–air mixer assembly using laser flow diagnostic techniques. Two experimental configurations are designed with different pilot fuel injection mechanisms and different swirl configurations. The injector assembly is realized using additive manufacturing methods. Direct laser sheet imaging and particle image velocimetry experiments are conducted to capture the air velocity field and atomization characteristics. The efficacy of the coaxial annular fuel injection mechanism on the atomization characteristics and high swirl number configurations on the external aerodynamics are presented qualitatively.

Ayush Divyansh, Preetam Jamod, K. P. Shanmugadas
Experimental Study on GDI In-Cylinder Combustion Quality of Ethanol and Lemon Peel Oil

A Gasoline Direct Injection (GDI) engine’s performance and emissions are greatly impacted by the fuel injection phenomena. It is critical to understand biofuel’s spray structure and combustion quality before using it in a GDI engine. This study investigates the combustion quality at different Start of Injection (SOI) timings using an optical GDI engine. Lemon Peel Oil (LPO) and ethanol are prepared on a volume basis, and three different SOI timing are selected to study the spray effect on combustion. Two binary blends and one ternary blend are prepared in different volume bases for this purpose: G60L40 (60% gasoline and 40% LPO), G80E20 (80% gasoline and 20% ethanol), and G40E20L40 (40% gasoline, 20% ethanol, and 40% LPO), and the effect of the thermophysical properties of the fuel blends on combustion characteristics are evaluated. In-cylinder combustion imaging revealed that injection timing significantly impacts combustion. The addition of ethanol improves the combustion, but LPO blends showed higher residence of diffusion burning due to poor evaporation characteristics.

B. Abinash, B. Yogesh, G. M. Nayak, V. W. Ketan, P. S. Kolhe, B. Saravanan
Numerical Study on Soot Formation of Methyl Methacrylate Pool Flames with Coflow Air

Polymethyl methacrylate (PMMA) is a polymer, and it finds its application in construction, transportation and domestic sectors. However, it is flammable. The combustion and soot characteristics of this polymer can be better understood by studying its monomer methyl methacrylate (MMA) that forms as a dispersed layer at the PMMA surface when heated to 250–300 °C. MMA is prone to produce soot. The effect coflow air towards mitigation of soot is analysed numerically considering MMA pool combustion. A parametric study is carried out with 30 mm pool diameter and 3 mm ullage for different amounts of coflow air (50, 100 and 150% theoretical air). Mass loss rate is observed to be almost the same for all the cases. However, the soot ratio is more for the reference case without coflow air, and it decreases for 50 and 100% theoretical air cases. The soot ratio increases when the coflow air increases from 100 to 150% theoretical air. The reasons for these trends are explained with the help of temperature, soot volume fraction, soot precursor, soot oxidation rate and OH contours.

Argha Bose, D. Shanmugasundaram, V. Raghavan
Impact of Computational Domain and Cell Type on Large Eddy Simulations in OpenFOAM for a Turbulent Partially Premixed Flame

Large eddy simulations (LES) are becoming state-of-art for industrial combustion applications due to its capability to better capture fluid mixing and flame front by resolving large-scale turbulent eddies. However, this increased sensitivity to the physics can become more demanding on the numerical and meshing methods and boundary condition requirements. This paper highlights some challenges in performing LES of a canonical turbulent partially premixed flame (Sandia flame D) in open-source CFD platform OpenFOAM. Both RANS and LES approaches were evaluated, and it was found that time-averaged flow and combustion properties were captured by RANS with reasonable ease and accuracy. However, LES was not able to capture the flame eddies and turbulent diffusion at the first attempt. LES results were found quite sensitive to the computational mesh and modelling methods. As the flow unsteadiness is captured in LES, the turbulence and acoustic boundary conditions also become important. Explorations on all these aspects are made, and finally, conclusion is made on the importance of using structured mesh over unstructured mesh and avoidance of two-dimensional axisymmetric domains in the OpenFOAM CFD solver, specifically in the LES context.

Sandeep Lamba, Krishna Kant Agrawal
Exergy Analysis of Deflagration Wave Propagating in Autoignitive H2 Mixture for Constant Pressure Boundary Conditions

Exergy analysis has been performed on propagation of deflagration wave in autoignitive H2-air medium. Various one-dimensional (1D) direct numerical simulations (DNS) have been performed with constant pressure boundary conditions. The analysis is performed with multiple initial pressures and equivalence ratios. During autoignition in stratified mixture, flame like structure (deflagration wave) originates from thermal or compositional inhomogeneity inside the domain. In present study, the deflagration wave propagating from the hotspot is allowed to interact with the autoigniting mixture. Three major components are identified for the exergy loss from the system: heat conduction, mass diffusion, and chemical reactions. The results show that the 1D simulation shows larger ignition delays than the homogeneous simulations (0D). The irreversibilities associated with the reactions are found to be major contributors to entropy generated during combustion. During the interaction of deflagration wave and autoignition spot, the contribution of conduction and diffusion irreversibilities is observed to reduce. Whereas the contribution of reaction irreversibilities increases. For low-pressure combustion (10–20 bar), the ratio of exergy loss and heat release rate is observed to reduce during the interaction of deflagration wave and autoignition spot.

Rahul Patil, Sheshadri Sreedhara
Numerical Investigation of Combustion Dynamics in a Multi-element Combustor Using Flamelet Approach

This paper investigates combustion dynamics in a complex multi-injector element combustor using a flamelet approach in a large eddy simulation (LES) framework. The capability of computationally less expensive chemistry tabulation method to capture the interaction between unsteady heat release and acoustics is investigated. A non-adiabatic steady flamelet-based tabulated chemistry closure is invoked to simulate hydrogen–oxygen reactions in mixture fraction space. The model incorporates flow-induced non-equilibrium flame effects through scalar dissipation rate and the turbulence-chemistry interaction using a probability density function (PDF). A multi-element combustor dynamic study captures the first tangential mode close to 4000 Hz and corresponding high-frequency harmonics appropriately. Spectral analysis of the pressure variation displays similar frequency features in chamber and injector sections, suggesting the possibility of injector-chamber coupling. The coupling of the transverse pressure waves in the combustion chamber with the longitudinal pressure oscillations in the oxidizer post was probed as the reason for the pressure dynamics observed in the combustor.

Abhishek Sharma, Ashoke De, Varghese M. Thannickal, T. John Tharakan, S. Sunil Kumar
Experimental Investigations on Emissions and Performance of Spark Ignition Engine Fuelled with Butanol–Pentane–Gasoline Blends

Current energy demand has led to an increase in fossil fuel consumption. Sources of fuels have been depleting over decades. Hence, there is a need to find alternatives to gasoline and diesel in the automotive industry. Alcohols are promising oxygenates and octane boosters for gasoline. The current investigation deals with blending butanol in 20% volume along with 10% pentane to gasoline in spark ignition engine in variation with spark timing from 15°, 18°, 21°, 24°, 27°, 30° bTDC. The performance and emission characteristics of fuel have been compared with base gasoline with 1800 rpm engine speed. Here, the results show a decrease in carbon monoxide emissions and a decrease in oxides of nitrogen emissions due to the addition of butanol, brake-specific fuel consumption increases for a butanol–pentane–gasoline blend. The optimum performance of the engine is at a spark timing of 24° bTDC.

Parag P. Mangave, Vishal V. Patil, Nilesh D. Pawar, Ranjit S. Patil
CFD Analysis of Afterburner with Convergent–Divergent Nozzle for Various Air–Fuel Ratios

Military jet aircraft fitted with afterburner gets additional thrust in extraordinary circumstances like combat. The jet aircraft must work in wide-ranging temperatures with different air–fuel ratios under varying circumstances. However, many researchers observed that jet aircraft operating with the lean air–fuel configuration is associated with instabilities, which is not under the scope of this paper. In the present paper, the afterburner, consisting of a convergent–divergent nozzle and essential components, is simulated for varying air–fuel ratios from 16 to 45 to check the effect of the increase in the fuel supply. Accordingly, the afterburner is modeled with liner, diffuser, V-gutter, fuel manifolds, and casing with a convergent–divergent nozzle. Computational fluid dynamics analysis is carried out with the help of Ansys Fluent® using SIMPLE algorithm, realizable k − ε turbulence model, energy equation, species transport, and discrete phase with finite-rate/eddy-dissipation model for combustion. The simulations were carried out for various air–fuel ratios 16, 19, 23, 30, and 45. Out of these different afterburner models, the afterburner with the minimum air–fuel ratio of 16 is found to attain the maximum velocity and maximum thrust. These results also match the experimental results of Useller et al. (Influence of combustion chamber length on afterburner performance. Lewis Flight Propuslion Laboratory, Cleveland, 1954, [1]).

Gurrala Srinivasa Rao
Computational Analysis of the Thermo Hydrodynamic Characteristics in a Can-Type Gas Turbine Combustor

The present work performs numerical simulations of a can-type gas turbine combustor. The fuel in the present study is taken as methane. The stoichiometric ratios for the correct amount of fuel–air mixture required in the combustor are calculated using a Python program. The number of fuel injector inlets is six, which are symmetric to the center of the combustor. The number of secondary air inlets is kept as four and symmetric to the center. The standard k − ε model is used because of the strong turbulence after the injector nozzle. This is also clearly observed from the findings that as we move along the length of the combustor toward the outlet, the profiles of velocity and static pressure and temperatures become symmetric and more uniform and steadier. Mass fractions of O2 and CH4 increase along the axis, and the overall pressure loss coefficient values reach nearly 5%.

Mohit Bansal, Satyam Dewivedi, Abdur Rahim
Experimental Study of Acoustic Phenomenon in a Closed Combustion Chamber

This study is aimed at obtaining data from pressure waves generated by the flame front and studying their effects on the formation of tulip flame. A closed rectangular chamber made of acrylic sheets is used for the experiment with premixed propane-air mixture for the combustion process. Equivalence ratio of 0.9, 1.0, and 1.1 are tested for the combustion. Microphones are used to measure pressure signals. In order to see the variation of the pressure wave characteristics at different instances of the combustion process, the microphone is placed at different locations. Data acquisition from the microphone is done through an oscilloscope. The signals are then analyzed to see different aspects of the recorded pressure signals.

A. Ananthakrishnan, Siba Prasad Choudhury, S. Syam, Ratan Joarder
The Effect of Lean Premixed Combustion on Thermoacoustic Instability in a Swirl Combustor

Combustion instability is a large amplitude oscillation of one or more natural acoustic modes of the combustion chamber. It is the outcome of advancement in the modern engine to reduce emission and fuel consumption by maintaining the lean equivalence ratio. It creates large amplitude pressure and velocity oscillation which results in thrust oscillation, severe vibrations, enhanced heat transfer, thermal stress, and failure of the system. In this work, a laboratory model swirl combustor with a lean mixture has been simulated to understand the mechanism of combustion instability. A 3D unsteady Reynolds-averaged Navier–Stoke numerical simulations are performed to understand the effect of lean premixed combustion on combustion instability. The results show that flame fluctuation due to lean premixed combustion leads to heat release oscillation. Heat release oscillation leads to pressure and velocity oscillation which results in combustion instabilities. The amplitude of pressure and velocity oscillation increases with time and finally become saturates. The numerical model is validated with experimental results.

Subhash Kumar, Sanjeev Kumar, Sheshadri Sreedhara
Computational Modelling of MMH/NTO Combustion in a Multi-element Triplet Injector Combustor

This paper presents the computational methodology developed to simulate monomethyl hydrazine/nitrogen tetroxide (MMH/NTO) combustion. A three-dimensional rocket scale combustor domain with multi-element triplet injectors is utilized to study hypergolic flow and flame features. A Eulerian–Lagrangian framework is invoked for continuous phase treatment of combustion gas and discrete phase treatment for both MMH and NTO droplets. A discrete particle-based method (DPM) with finite rate chemistry is employed to study droplet injection, evaporation, and combustion. A description of flow and flame characteristics in three-dimensional RANS framework is presented in this paper. The model captures impinging jets from multiple triplet injectors, and MMH film cooling injection appropriately. It presents physical trends on the core combustion process, as well as the global evolution of temperature, pressure, and droplet spray in the combustor. The focus of the study is to develop a hypergolic combustion model which can be used to predict combustion performance under off-nominal operating conditions. The aim is to extend the model to study the combustion instability aspects of MMH/NTO-based combustors.

Abhishek Sharma, Varghese M. Thannickal, T. John Tharakan, S. Sunil Kumar


Novel Tree Branching Microchannel Heat Sink Under Variable and Constant Fluid Volume Approaches

In this work, two designs of radial tree branching microchannel heat sinks (TB-MCHSs) are proposed: (i) TB-MCHS with continuously increasing channel depth from the centre inlet to the radial outlet (TB-MCHS-DIV) and (ii) TB-MCHS with continuously decreasing channel depth (TB-MCHS-CON). Thermo-hydrodynamic performance of TB-MCHS-DIV and TB-MCHS-CON is numerically evaluated and compared with TB-MCHS with constant channel depth (TB-MCHS-ST). The present work is carried out in two scenarios: In the first scenario, the fluid/channel volumes of TB-MCHS-DIV and TB-MCHS-CON are significantly more than TB-MCHS-ST, whereas in the second scenario, the same is nearly equal to that of TB-MCHS-ST. The results reveal that in the second scenario compared to TB-MCHS-ST, the proposed design shows slightly higher (~ 3%) average heat transfer coefficient, whereas it also shows higher (~ 7%) pressure drop. However, in the first scenario, the proposed design shows lower (~ 8%) average heat transfer coefficient than the TB-MCHS-ST, whereas it also shows lower (27%) pressure drop. The substantial reduction in the pressure drop dominated the reduction in heat transfer coefficient resulting in the performance evaluation criteria (PEC) value more than unity for the proposed design based on the variable fluid volume approach.

Sangram Kumar Samal, Sandip Kumar Saha
Two-Dimensional, Magnetic Actuation of Ferrofluid Droplet on an Open-Surface Microfluidic Platform

The role of non-contact manipulation of discrete droplets on surface microfluidic platforms has wide applications in development of low-cost biosensors and biomedical diagnostic systems. Magnetic digital microfluidic platforms utilize magnetic force to actuate ferrofluid droplets on open hydrophobic surface and offer distinctive benefits compared to other digital microfluidic actuation schemes. This allows droplets—containing different type of sample and reagents—to be actuated and controlled independently; this can be leveraged to achieve different bioanalytical protocols for point-of-care diagnosis and other different micro-total analytical systems. Here, investigate, through a physically realistic model, magnetic field-actuated transport of a spherical cap ferrofluid droplet on a surface microfluidic platform. Manipulation of a microliter volume droplet in a sequence of rectilinear paths, leading to a guided transport, is achieved through an array of double-layer, planar, square-shaped electromagnetic micro-coils embedded in the substrate. Appropriate sequence of coil energization for attaining the desired trajectory of the droplet is described. The study paves the foundation of developing more complex digital microfluidic devices for different biomicrofluidic applications.

Debiprasad Chakrabarty, Niladri Chakraborty, Ranjan Ganguly
Numerical Analysis of Heat Transfer and Fluid Flow in Microchannel Heat Sinks Designed for Uniform Cooling

Liquid convective heat transfer for miniature heat sinks has proved to be efficient in heat dissipation from electronic components of shrunk scales. The current numerical study presents a novel fin topography for microchannel heat sink which has been more efficient than conventional straight channels in uniform cooling. Unlike inlet plenums, the design includes flow to the heat sink (lower plate) entirely through jets with an optimized pattern, which has been designed to account for uniform cooling. The temperature distribution over the heating surface (the surface to be cooled) of the novel design has been compared to that of a straight microchannel with rectangular fins of 0.8 mm height with 1 mm wall height. Comparison between novel design and straight channels has been done using standard deviation for the same heating surface area of 645.16 mm2. A constant heat flux of 50 × 10−2 W/mm2 has been used throughout the numerical analysis. Enhanced uniformity of cooling comes at the expense of increased pressure loss. Steady flow in both laminar and turbulent regimes was analyzed with appropriate models. The results suggested that the novel design would be much more suitable for turbulent flows of liquid-cooled systems than laminar.

Shivayya C. Hiremath, Rohit Kumar, Arman Mohaddin Nadaf, Manmohan Pandey
Numerical Investigation on Hydrodynamics of Lubricant-Infused Hydrophobic Microchannel with Transversely Oriented Cavities

Higher values of pressure drop due to the resistance offered in the microchannel can be dealt with the introduction of fluid within the microgroove surfaces of a microchannel. The non-uniformity in the groove shapes observed calls for an extensive study to determine which geometry contributes to higher drag reduction because of an increase in the volume of entrapped fluid. It is also to be noted that the inherent viscosity of the infused fluid can also govern the effective slip length value. Hence, the present study contributes to the enhancement of drag reduction of a lubricant-infused hydrophobic microchannel for isothermal conditions. In Stokes’s regime, the effect of varying the geometrical parameter of a lubricant-infused cavity showed a significant reduction in the flow resistance inside the microchannel. Present study recorded that the increase in cavity area and high aspect ratio reduces hydrodynamic resistance. Further, low viscosity ratio ribbed channels are suitable for internal fluid applications.

Adarsh R. Nair, K. Nandakumar Chandran, S. Kumar Ranjith
Effect of Microstructures in the Flow Passage on the Flow Dynamics of Microchannel

The microchannels serve as a heat dissipation device in the miniaturized—high performance electronic components. The incorporation of microstructures in the flow passage of microchannel helps to increase the rate of heat dissipation due to the flow interruption, acceleration, increase of heat transfer surface area, boundary layer deformation, etc. However, the flow dynamics is the integrated part of the heat transfer. This manuscript deals with the effect of various arrangements and cross-sections of microstructure in the flow field. The pressure drop increases as the microstructure splits and the space between the split microstructure increases. The cross-section and velocity of fluid flow influence the skin friction coefficient on the surface of the microstructure. The trend of variation of pressure drop and drag coefficient is almost the same.

A. Rajalingam, Shubhankar Chakraborty
Combined Effect of Heterogeneous Zeta Potential on Microchannel Wall and Conductive Link in Induced Charge Electrokinetic Micromixing

In this paper, a variation of induced charge electrokinetic (ICEK) micromixing is investigated numerically. The channel walls are subjected to heterogeneous zeta potentials. Further, conductive links are also employed inside the channel to enhanced mixing. The primary aim is to understand the influence of control parameters (i.e. zeta potential, number of conductive links, their orientation and applied electrical potential) on mixing efficiency. Heterogeneous zeta potential creates recirculation zone in the flow and increases the interferential contact between the fluids layer, hence improving the mixing. Further, the conductive links induce the micro vortices which enhance the mixing. The induced charge on the conductive link is calculated using correction model. Results show that the mixing efficiency increased by two times when conductive link inside the channel and heterogeneous zeta potential patch on wall is mounted. It is also observed that the mixing efficiency increased as the number of links and patches increased.

Anshul Kumar Bansal, Ram Dayal, Manish Kumar
Analysis of Sperm Cell Kinetics in Newtonian and Non-Newtonian Fluid Medium Within a Microfluidic Channel

The success of the internal fertilization process results from the successful migration of sperm through the female reproductive tract. During the course of motion, sperm must overcome the obstacles and chemical changes that occur in their path towards the oocyte. Herein, we conducted an experimental and simulation study of sperm in different fluid medium, whose rheological properties mimic the actual environment of the female reproductive tract. In this work, two surrounding mediums of sperm are prepared by diluting Polyvinylpyrrolidone (PVP) and Methylcellulose (MC) in Phosphate-buffered saline (PBS). They exhibit Newtonian and Non-Newtonian behaviour, respectively. Sperm motility and kinetic parameters such as velocity, beat frequency, forces, power and swimming efficiency are calculated. The results indicate that sperm possesses high straight-line velocity, curvilinear velocity and beat frequency in MC 2% Non-Newtonian fluid. The Drag force, power output, the power required for sperm motion and sperm swimming efficiency are high in Non-Newtonian fluid compared to the Newtonian fluid of the same viscosity range.

Dhiraj B. Puri, Vadiraj Hemadri, Arnab Banerjee, Siddhartha Tripathi
Conjugate Heat Transfer Analysis of U-Bend/Turn Microchannel: A Computational Approach

To examine the fluid flow and heat transfer properties of a U-shaped bend microchannel, a three-dimensional single-phase numerical study involving the conjugate effect of heat transfer is analyzed. The hydraulic diameter of the geometry was constant (0.4 mm) and the radius of curvature was varied from 2 to 4 mm. The constant heat flux boundary condition was applied at the bottom of the substrate and a comparative study with a straight conventional microchannel design is presented in terms of the performance evaluation factor. Different flow rates were considered to evaluate the effect of secondary flow in the form of Dean Vortices. Non-dimensional heat transfer parameter such as the average Nusselt number and frictional losses in terms of pressure drop was evaluated and the contours of temperature and velocity were analyzed to elaborate the effect of heat transfer enhancement in the bend microchannel. Higher radii of curvature improved the overall performance of the bend channel. At a lower radius of curvature, the performance of the bend microchannel can be improved with increased pumping power. Due to unavoidable pressure loss in the case of microchannel, it is advisable to use U-bend microchannel at relatively low flow rates and higher radius of curvature.

Jyoti Ranjan Mohapatra, Manoj Kumar Moharana
Experimental Investigation of Fluid Flow Behaviour in Parallel Microchannel Using Micro-PIV

With the miniaturization of the system, the demand for high heat flux removal technologies increases. Innovative technology is the use of microchannel using water as a coolant which can handle the high rate of heat fluxes. For a given pumping power, the rate of flow through the microchannel is low, therefore, many microchannels operating in parallel are required. In this present work, an experimental study of flow through three rectangular parallel microchannels has been carried out. The experiments are performed using micro-PIV at various flow rates and different concentrations of the seeding particles. The post-processing of raw images captured during the micro-PIV experiment is done by PIV Labs software. The experimental analysis is done for various parameters like the concentration of seeding particles and the effect of flow rates. Experimental results are compared with analytical solutions for the parallel microchannel.

Rohit Kumar, Chandan Nashine, Arman Mohaddin Nadaf, Mohd Sakib Hussain, Manmohan Pandey
Study of Path Selection of a Droplet in a Symmetric Y-Microchannel Using a Uniform Electric Field

The droplet dynamics in a symmetric bifurcating Y-microchannel under the influence of a direct current (DC) electric field imposed across only one daughter channel are investigated. The interface of the droplet has been captured using Cahn–Hilliard equation, while the effect of electric force at the droplet interface has been incorporated by modelling it as a body force term in the momentum equation. Two different sorting behaviours of the droplet have been observed depending on the relative permittivity ratio ( $$\varepsilon_{{\text{r}}}$$ ε r ) of the droplet and carrier fluid and the choice of daughter channel where electric field is imposed. The droplet chooses the path of the channel where the electric field is applied if its permittivity is higher than that of the carrier fluid. The reverse phenomenon is seen to take place when droplet electrical permittivity is lower than that of the carrier. Furthermore, it is also observed that by altering the intensity of the electric field, it is possible to accurately regulate the daughter droplet breakup ratio in a Y junction and reach droplet of any size. We have also identified a critical electric Capillary number (Cae) at which the droplet completely transcends from breakup to no-breakup regime and gets sorted in any one branch channel depending on $$\varepsilon_{{\text{r}}}$$ ε r and the branch channel where the electric field is imposed. The increase in Cae beyond its critical value doesn’t affect the no-breakup regime but increases droplet velocity and facilitates a bit faster sorting than the previous droplet.

Satya P. Pandey, Sandip Sarkar, Debashis Pal
Microfluidic Solute Transport by Interference of Oscillatory Thermal Marangoni Effect and Patterned Wall Slip

For quick sample processing, the reagents’ mixing is crucial in microfluidic devices. However, it is difficult to obtain efficient mixing at such small scales due to low Reynolds number $$\left( {{\text{Re}}} \right)$$ Re flow within the micro-conduits. We study fluidic-transport and mixing phenomenon in a binary-liquid system by the thermocapillary effect, actuated by the periodic wall thermal stimuli. Our study also demonstrates the impact of the interference of thermo-capillarity and wall slip on the behavior of the phenomena mentioned above, by employing patterned wettability at the wall surfaces. We semi-analytically solve the Navier–Stokes and the continuity equations to obtain the hydrodynamic characteristics of the system. We also solve the species transport equation to obtain the solute distribution in the microchannel for given inlet concentration conditions. Our study explores different mechanisms through which the flow pattern can be morphed to enhance the solute particles’ mixing. The present work illustrates the direct relationship between mixing dynamics and wall slip through the qualitative study of the stream function and solute distributions within the microchannel.

Shubham Agrawal, Prasanta K. Das, Purbarun Dhar
Analysis of Micro-nozzle Flow Using Navier–Stokes and DSMC Method and Locating the Separation Plane Based on Modified Knudsen Number

The flow through a micro-nozzle was studied using the particle-based DSMC approach and continuum approach using Navier–Stokes. Slip and no-slip boundary conditions are examined for the Navier–Stokes approach. The results are compared with the full DSMC simulation of a micro-nozzle with a 2 µm diameter. Predictions from all three methods are very close in the converging section. However, due to an increase in rarefaction effects, there are variations in the parameters observed at the diverging section of the nozzle. The extent of rarefaction is plotted using the Knudsen number isocurves inside the nozzle. To account for the local variation in characteristics length, Knudsen number is derived based on different properties like pressure, temperature, and density. The Knudsen number isocurves show that the continuum assumption breaks down at the throat, and the effects of rarefaction increase toward the nozzle’s exit.

Ashok Kumar, Manu K. Sukesan, Shine S. R.
Parametric Study on the Primitive Lattice Using the Pore-Scale Simulation to Characterize the Flow and Heat Transfer Performance

In this study, a Primitive lattice based on Triply Periodic Minimal Surfaces (TPMS) is used to build a porous structure for performing a combination of pore-scale numerical simulation along with the porous media flow simulation. On the three-dimensional lattice, numerical analysis is performed for single-phase fluid subjected to uniform heating at the walls. The void subdomain of the lattice is designated as the fluid zone, to perform the pore-scale numerical simulations; whereas, the solid subdomain of the lattice is designated as the microporous zone to perform porous transport simulations. The parametric studies for overall pressure drop and heat transfer coefficient are performed for a range of permeability of microporous zone. It is shown that when the micro-permeability is increased in the range $$10^{ - 10} < {\text{Da}}_{\mu } < 10^{ - 5}$$ 10 - 10 < Da μ < 10 - 5 , there is no significant change in pressure drop as well as the heat transfer coefficients. On the other hand, increase of micro-permeability in the range of $$10^{ - 5} < {\text{Da}}_{\mu } < 10^{ - 1}$$ 10 - 5 < Da μ < 10 - 1 causes a sharp drop in the pressure drop and a marginal drop in the effective heat transfer coefficient. Therefore, replacing the solid zone with porous zone for the solid subdomain of the lattice provides an improved thermo-mechanical performance for the mini-channel even in the low flow rate regime ( $${\text{Re}} = 10$$ Re = 10 ).

Surendra Singh Rathore, Balkrishna Mehta, Pradeep Kumar, Mohammad Asfer
Experimental and Numerical Studies on Liquid Bridge Stretching in Uni-port Lifted Hele-Shaw Cell for Spontaneous Fabrication of Well-Like Structures

The formation of liquid bridge between solid surfaces is of interest to fluid dynamics researchers due to the rich flow physics in the problem, as well as its various applications in engineering and biology. In this work, we propose a technique to spontaneously fabricate well-like structure by stretching the liquid bridge of highly viscous fluid in uni-port lifted Hele-Shaw cell (ULHSC). The numerical simulations are used to characterize optimal set of flow parameters for which wells are formed. Results from the simulations also yield insight into the flow physics governing micro-well formation. In the numerical simulation study, single hole is incorporated in the lower plate and upper plate is lifted with the uniform velocity. Parametric characterization of the system reveals that growth rate of the air bubble through the uni-port depends on the size of the hole diameter on a lower plate. Experiments are carried on ULHSC for two different holes diameters on bottom plate at same capillary number. Overall, the paper develops insights towards shaping of fluid in 3D well-like structures using ULHSC via numerical simulation and experimental studies.

Makrand Rakshe, Sachin Kanhurkar, Amitabh Bhattacharya, Prasanna Gandhi
Numerical Investigation on Inertial Migration of Spherical Rigid Particle in the Entrance Region of a Microchannel

In this work, numerical investigation of inertial migration of neutrally buoyant rigid spherical particles in the entrance region of a microchannel is performed. Typically, inertial migration is examined for particles in a developed flow, in contrast, particles in developing flow are examined here. The entrance region having two-dimensional flow and fully developed region with the uni-directional flow is simulated with Re = 60 and a blockage ratio of 0.25. The particles are released from vertical positions of y/2H = 0.497 (center) and y/2H = 0.106 (near wall). It is observed that the particles released in the entrance region cover a longer longitudinal distance before reaching the equilibrium position. Indeed, the time taken for the particles to arrive at the zero-lift position in the developing flow is 23.8% and 7.8% more than that of a fully developed flow.

K. K. Krishnaram, S. Kumar Ranjith
Dynamics of Electrically Actuated Carreau Fluid Flow in a Surface-Modulated Microchannel

The flow and mass transfer characteristics of an electroosmotic flow of Carreau fluid through a surface-modulated microchannel are presented. Flow is considered to be influenced by the coupling effect of both the externally applied electric field and heterogeneous zeta potential. The constitutive rheological behavior of the Carreau fluid is incorporated with the Nernst–Planck-Navier–Stokes-based flow governing equations to obtain the flow variation and species distribution depending on the behavior of the fluid properties. Moreover, the variation of electric double-layer thickness and the zeta potential provides a complex flow phenomenon, which can be beneficial for mixing enhancement. The results indicate the practical application of electroosmotic flow over heterogeneous patched surfaces observed in the lab-on-a-chip device used in Bio-MEMS and can handle inhomogeneous surface conduction and geometric interfacial disorder.

Subhajyoti Sahoo, Ameeya Kumar Nayak
Heat Transfer Analysis of Peltier-Based Thermocycler for a Microfluidic-PCR Chip

Polymeric chain reaction (PCR) is one of the commonly used technologies for the exponential amplification of a pathogen's DNA or RNA for quick detection. A common PCR procedure includes three major steps: denaturation (90–97 °C), annealing (50–60 °C), and extension (68–72 °C). This process is often repeated in 25–30 cycles, and it may take up to 5–6 h for successful amplification of the target DNA. The implementation of PCR in a microfluidic platform would reduce the reaction time drastically as it may consume only a few microliters of samples and reagents. Also, it increases the sensitivity and capability of point-of-care applications. A thermal analysis of a microfluidic device fabricated using thermoplastic (PMMA) is presented in this paper. The heating and cooling of the sample are done using two thermoelectric modules. The numerical analyses of the system are carried out for comparing the performance of thermoplastic materials during the thermal ramping process.

Nikhil Prasad, B. Indulakshmi, R. Rahul, Ranjith S. Kumar
Effect of Viscosity on the Margination of White Blood Cells in an Inertial Flow Microfluidic Channel

White Blood Cells (WBCs) play a significant role in defending and eliminating infection-causing external elements and are indicators of several diseases, such as inflammatory diseases, cancer, and allergies. Here, microfluidic devices have an upper edge in the accurate and fast processing of the sample, which is needed for speedy disease prediction. In specific, passive microdevices are valuable as they are simple, cheap, and effective compared to the current inefficient conventional methods. Here we have analysed the effect of viscosity on the margination of WBCs in inertial flow in a rectangular channel with a bifurcation. We added known concentrations of viscoelastic fluid to vary the viscosity of the sample. WBC margination was analysed from the values of WBC enrichment with respect to viscosities.

Dhiren Mohapatra, Rahul Purwar, Amit Agrawal
Experimental Investigation of Two-Phase Immiscible Liquid Flow Through a Microchannel

Two-phase flow is getting more and more applicable as component sizes in mechanical systems are miniaturized. The applications of two-phase microfluidic devices include energy conversions, chemical synthesis, and thermal management. Hence, the two-phase flow largely determines the functionality and performance of these devices. Immiscible two-phase liquid flow in microchannels has a wide area of applications such as extraction processes, emulsion production and other biochemical applications. Therefore, modern researchers are trying to study the flow dynamics of two-phase flow and its effect on microscale devices. In this work, experimental studies are done for flow visualization and determining flow patterns of the two immiscible liquids flowing through the microchannel using the inverted microscope, and the images are captured with a high-speed camera. The microchannel has a square cross-section with an area of 100 × 100 µm2 with two inlets and one common outlet. The liquids are passed through the T-shaped microchannel through their respective inlets. De-ionized water and silicone oil are selected as the working fluids for the experiment. Experiments are conducted for the different combinations of the flow rate of the fluids. The images are captured along the flow length at various locations to analyze the flow patterns inside the channel. The background noise of the captured images is removed by the postprocessing method. The processed images are analyzed using the Phantom Camera Application software to obtain the stratified length, bubble length, and bubble velocity of the flow regimes.

Rohit Kumar, Chandan Nashine, Arman Mohaddin Nadaf, Harish Kumar Tomar, Manmohan Pandey
Elastohydrodynamics of Electromagnetically Actuated Deformable Microfluidic Systems

Fluid structure interaction (FSI) resulting out of flow of Newtonian electrolytic fluid through a parallel plate microchannel having elastic walls has been semi-analytically investigated in this article. The fluid is exposed to external electric fields in the axial and transverse direction, and a magnetic field in the transverse direction. Taking in to account all the participating forces, a comprehensive examination of the two-way interrelationship between the flow hydrodynamics and channel deformation is presented in this article. Considering the case of constant flow rate within the channel, the variation of pressure distribution in the channel has been demonstrated for different flow rates and their effect in channel wall deformation. The velocity profile for different flow rates at different channel sections has also been depicted. For the case of constant pressure gradient in the channel, the channel wall deformation along the channel length has been depicted. The effect of magnetic field to bring about flow enhancement has also been explored in our study. The effect of the elasticity of channel walls on flow dynamics has also been investigated in this article.

Apurba Roy, Purbarun Dhar
Experimental and Numerical Analysis of Ferrofluid in Partially Heated Closed Rectangular Microchannel Tube Under Non-uniform Magnetic Field

This manuscript presents experimentally and numerical simulation works about the influence of convective parameters on single-phase, temperature-sensitive kerosene-based ferrofluid (1.36% vol. $${\text{Fe}}_{3} {\text{O}}_{4}$$ Fe 3 O 4 ) under the steady-state free convection in a partially heated thermomagnetic convection closed transparent rectangular tube loop under an external non-uniform magnetic field (created by a permanent magnet B = 1000 G). Several numerical simulations are performed to analyze various critical dimensions and nondimensionless factors such as magnetic field strength, velocity-temperature distribution, heat transfer augmentation, and Nusselt number (Nu) variation with an aspect ratio (L/D), in addition, understanding the two essential mechanisms, thermomagnetic convection and Kelvin body force (KBF) for fluid flow. The simulation results agreed with practical values obtained from the ferrofluid microchannel cooling system experiments. In addition, results validation of simulation and experiment model and grid analysis are discussed in this manuscript. The numerical results revealed that magnetizing force impacts the heat transfer rate, and the outcomes report shows that a magnetic field perpendicular to the temperature gradient can enhance heat transfer. The overall computational works are consistent with experimental results, and numerical results showed that the kerosene-based ferrofluid has good potential for coolant application under a controlled magnetic field and power resource.

Ramesh Kumar, Shivam Raj, S. K. Dhiman
Numerical Investigation on the Effect of Reynolds Number on the Droplet Bypass Through T-Junction Using Lattice Boltzmann Method

An effort has been made using lattice Boltzmann method to study the interfacial dynamics of a lighter liquid droplet (kerosene) in the high density liquid (water) bulk of the fluid flow, inside a T-channel with the variation of the Reynolds number. Droplet is kept in the vertical arm of the T-channel. Diffused interface concept has been used to capture the complex interface structure. Reynolds number of the fluid is varied in both horizontal and vertical arms. It is observed that with the increase of the Reynolds number in the horizontal arm, thickness of the droplet decreases and elongation of the droplet increases after the T-junction. The increase of Reynolds number in the vertical arm leads to an increase in the thickness of the droplet and a decrease in the elongation of the droplet after the T-junction. It is also observed that the tail end of the droplet is more bifurcated and sharper in the vertical arm as it approaches the T-junction.

T. Sudhakar, Arup K. Das, Deepak Kumar

Bio-fluid Mechanics

Blood Flow Modeling in Stenosed Arteries Using CFD Solver

Simulation of blood flow in arteries is an extensive topic of research to study various hemodynamic factors in CFD. This paper studies two different degrees of stenosis (less than 50 and 80% by flow area) that have been extracted from real images. The pulsatile nature of the blood flow has been considered. Changes in velocity flow patterns and wall shear stress for the two cases have been studied. Results show that the peak velocity increases drastically as the stenosis area increases to 80%. Negative velocity near the walls of the artery shows flow separation. This value also increases with the increase in stenosis area. This is seen in almost all regions of the cardiac cycle except in the accelerating flow region. With the increase in stenosis area, wall shear stress (WSS) rises drastically. Negative wall shear stress seen downstream of stenosis also indicates recirculation.

Priyambada Praharaj, Chandrakant Sonawane, Vikas Kumar
Highlighting the Importance of Nasal Air Conditioning in Septoplasty Using Virtual Correction Tools: A Numerical Study

Nasal air conditioning of the inspired air is one of the primary functions of the upper airway. However, it can get significantly altered due to abnormal changes in the nasal anatomy. Understanding the alteration in nasal air conditioning in a non-invasive manner is essential for effective septoplasty planning. Therefore, the current study aims to investigate this alteration due to nasal septum deviation with the help of computational fluid dynamics (CFD). Additionally, its relevance in septoplasty planning has been demonstrated using the virtual septoplasty technique. A patient-specific nasal cavity model having S-shaped deviation has been reconstructed using the CT scan images, which are virtually corrected to mimic septoplasty. The computational model is employed to investigate the alteration in airflow velocity, pressure drop, wall shear stress, relative humidity, and water mass fractions in deviated and virtually corrected cases. The insilico results demonstrate that deviated nasal septum (DNS) leads to asymmetric distribution of airflow velocity and water mass fractions, which becomes symmetric in both the cavities after the virtual septoplasty procedure. Additionally, there is an increase and decrease of relative humidity and pressure drop, respectively, in virtually corrected case that leads to delivery of saturated air to the lungs and ease in breathing.

Kartika Chandra Tripathy, Ajay Bhandari
Thrombosis Modelling in a Stenosed Artery

This chapter presents a discussion on blood clotting in an idealized stenosed artery and its effect on the local flow dynamics. We make use of a simple residence-time-based model to mimic the clot growth. The blood flow is modelled using Ansys Fluent, while the clotting process is supervised using a UDF subroutine. Blood flow is considered to be Newtonian and non-pulsatile. We believe that the model presented in this chapter can be extended to study clotting patterns in geometries much more complex than the one presented here.

Prateek Gupta, Rakesh Kumar, Sibasish Panda, Mohammad Riyan
Gold Nanoparticle-Antibody Bio-Probe Analysis: Synthesis, Conjugation, Characterization and Dot Blot Assay on Paper

Gold Nanoparticle (AuNP) surface functionalized with antibodies is critical for the optimization and development of AuNP-enabled biosensing technologies. The optical properties of AuNPs and the binding specificity of antibody–antigen interactions help in the amplification of the assay signals in point-of-care technologies. Obtaining the stable AuNP–Antibody conjugate poses a major challenge as there is a chance of aggregation of the particles when the pH shifts. In this work, 37.7-nm sized spherical citrate-capped AuNPs are synthesized and are conjugated with Anti-25-OH vitamin D3 antibodies using a direct physical absorption method which requires no chemical functionalization of the AuNP or the antibody surface. The UV–vis spectroscopy and DLS outputs are used to characterize and prove the efficiency of the system. The UV–vis analysis is used to indicate the adsorption of antibodies onto the AuNP surface with the change in the absorbance peak. It was observed that the negatively charged AuNPs binded to the positive charge of the antibodies to form effective bioprobes for further detection of antigen in a short time as well as visible to the naked eye. The AuNP-Ab bioprobe’s stability and efficiency were checked with repeatability under 24 h observation.

Prateechee Padma Behera, Shubham Kumar, Monika Kumari, Pranab Kumar Mondal, Ravi Kumar Arun
A Computational Analysis of the Impact of Blood’s Viscoelastic Properties on the Hemodynamics of a Stenosed Artery

Treatment of atherosclerotic diseases, including stenosis and arterial aneurysms, requires a more accurate prediction of hemodynamic flow features. In addition to the degree of stenosis and the body’s physiological state, blood rheology substantially impacts the haemodynamics of a stenosed artery. The current study shows how the assessment of hemodynamic wall indicators is affected when blood viscoelasticity is taken into account as opposed to when it is ignored. For this, multi-mode Giesekus and Simplified Phan-Thein/Tanner (sPTT) models were used to mimic the rheology of real and whole blood. The finite volume-based solver rheoFOAM, part of the rheoTOOL package, was used to run numerical simulations in a planar 75% stenosed artery. The Newtonian and Carreau-Yasuda model (for purely shear thinning fluid) were also used to carry out numerical simulations, together with the non-linear viscoelastic models. The post-stenotic zone’s temporal streamwise velocity evolution at various planes demonstrates how the flow separation zone’s size and symmetry rely on the blood’s rheology. When the blood’s elasticity is taken into account, there are much fewer reattachment points, which is a sign of the number of recirculation zones along the artery wall during one cardiac cycle. Additionally, non-linear viscoelastic models predict higher values of hemodynamic wall indicators than the Newtonian and Carreau–Yasuda models. The current data demonstrate that the blood’s rheology cannot be discarded when computational fluid dynamics simulations are employed as a tool in the diagnosis, prevention, and treatment of severely stenosed arteries.

Sourabh Dhawan, Pawan Kumar Pandey, Malay Kumar Das, Pradipta Kumar Panigrahi
Effect of Induced Helicity on the Hemodynamics of Carotid Artery Passage

Abrupt narrowing of the carotid artery known as atherosclerosis is a common cardiovascular disease, increasing the risk of stroke which is one of the leading causes of death. Helicity in the arterial passage is found to be one of the effective ways to minimize plaque formation. Using Autodesk Meshmixer, an open-source software, the stenosed portion of the diseased artery is removed to obtain what is referred to in this study as the base case. The helicity and hemodynamic characteristics of a patient-specific geometry with and without stent in repaired instance are examined. The current study found that when novel stent design is placed there is a reduction in recirculation zone size and Relative Residence Time (RRT), but also resulted in increased pressure drop across the artery.

L. Rakesh, Arun Kadali, K. Prakashini, S. Anish
Numerical Simulation of Flow in an Idealized Intracranial Aneurysm Model to Study the Effect of Non-newtonian Blood Flow Rheology

Rupture risk assessment of intracranial aneurysms has gained relevance in the recent years. Serious health issues such as Subarachnoid Haemorrhage (SAH), damage to the brain and death can occur if an aneurysm ruptures. Rupture risk prediction based on size cannot be considered accurate. There is no clinical method to predict rupture risk of aneurysm so far. Computational modelling is highly relevant in the study of aneurysms since the experimental approach is difficult. Thus, the rupture risk can be predicted using Computational Fluid Dynamics (CFD). Although blood has non-Newtonian rheology, most CFD research to date have assumed Newtonian behaviour. Comparative study of various available non-Newtonian models and scope of developing a reliable model for intracranial blood flow simulations still remains. In the present work, numerical simulations have been carried out on idealized 2D half spherical aneurysm geometry to study the basic flow patterns and the impact of blood rheology on wall shear stress (WSS).

Suraj Raj, S. Anil Lal, Anjan R. Nair
On the Replication of Human Skin Texture and Hydration on a PDMS-Based Artificial Human Skin Model

In the current study, we have developed an artificial skin sample and replicated the textures and hydration of the human skin on it. Polydimethylsiloxane (PDMS), Polyvinyl alcohol (PVA), and Glutaraldehyde (GA) are used to fabricate an Epidermal Skin Equivalent (ESE) of human skin. Additionally, a PVA-based hydrogel is synthesized, and its hydration property is examined at varying concentrations of PVA. The values of roughness (6.2–10.8 μm), wettability (72–122°), and hydration (10–40% after 24 h) of artificial skin samples fabricated in the present study are found to be very close to that of human skin. The hydration of PVA hydrogel is observed to increase (17–96%) with an increase in PVA concentration (10–30%). Our results highlight that the fabricated artificial skin model closely resembles the surface and hydration characteristics of human skin.

Aditya Ranjan, Vijay S. Duryodhan, Nagesh D. Patil
Simulation of Lateral Migration of Red Blood Cell in Poiseuille Flow Using Smoothed Particle Hydrodynamics

Cell separation is a process of isolating one or more specific cell populations from a heterogeneous mixture of cells. Understanding the dynamics of cells in different flow conditions is necessary to develop and improve the cell separation methods based on mechanical properties of cells. The present work numerically investigates the lateral migration of a deformable red blood cell in Poiseuille flow and the effect of the initial position of the cell on migration time and final shape of RBC. A meshless particle-based method known as smoothed particle hydrodynamics (SPH) is used in the simulations, which has several advantages over conventional grid-based methods in simulating fluid–structure interactions problems involving large deformation. A numerical model has been developed using a modified SPH that implements various improvements reported in the literature. The numerical simulations are parallelized on GPU using CUDA Fortran. The developed numerical model has been validated with existing results in the literature and it captures the deformation and migration of the deformable cell very well. It is observed that the RBC migrates towards the centre and attains similar shape at steady state irrespective of the initial position.

Justin Antony, Ranjith Maniyeri
Effect of Stenosis Severity on the Hemodynamics of an Idealized Straight Arterial Tube

The present study examines the effect of stenosis severity on arterial hemodynamics using the immersed boundary method-based in-house numerical code. A realistic physiological velocity waveform varying in time and parabolic in space is adopted as an inlet boundary condition in a straight arterial tube with single asymmetric stenosis. The flow is considered to be laminar and incompressible, assuming blood as a Newtonian fluid. The degree of stenosis (DS) is defined by the obstructed cross-sectional area. The velocity and vorticity contours demonstrate that increment in DS results in further disturbances in the flow downstream of the stenosis. The areas with low Time-Averaged Wall Shear Stress (TAWSS) and high Oscillatory Shear Index (OSI) are more prone to further plaque deposition, and areas with high TAWSS, such as throat of the stenosis, are potential sites for thrombus formation. The magnitude of the peaks in the cyclic pressure drop across the stenosis rises with its severity. However, in the present study, a greater pressure drop is noted at 45% stenosis (DS45) case as compared to 65% stenosis (DS65) case as some pressure recovery occurs in the latter case.

Pawan Kumar, Somnath Roy, Prasanta Kumar Das
Microdevice for Plasma Separation and in Vitro Quantification of Plasma Proteins

Recent advances in engineering have demonstrated the use of microfluidic devices as a platform for bioanalytical applications. Over the last few decades, microdevices for blood plasma separation are globally recognized due to their numerous benefits as compared to conventional techniques. One of the recently reported work from our research group has successfully demonstrated a simple and efficient passive microfluidic device capable of plasma separation from the whole blood. The design utilized bifurcated microfluidic channel dimensions of hundred microns for separating plasma with almost 100% separation efficiency. In the present research, we report blood plasma separation using this microfluidic chip and in vitro quantification of albumin (plasma protein) using colorimetric techniques. Undiluted blood (hematocrit up to 45%) at a flow rate of 0.3–0.6 ml/min was used for performing experiments. The separated plasma was further utilized for the quantification of albumin. Albumin present in the plasma binds with a reagent Bromocresol green (BCG) to form a blue-green colored complex (Albumin-BCG). The intensity of the resultant color formed after mixing is proportional to the concentration of albumin. The absorbance of the colored complex at 628 nm was measured using a spectrophotometer for quantitative analysis of albumin. The concentration of albumin obtained from microfluidic-separated plasma was compared with that of albumin detected from centrifuged plasma. The comparative study shows that the results are within the reasonable limits of agreement (error of ± 3%). The potential outcomes of this research build confidence toward the design and development of microfluidic plasma separation and detection devices at large.

Tony Thomas, Neha Mishra, Amit Agrawal
White Blood Cell Separation and Blood Typing Using a Spiral Microdevice

Our immune system is shielded from various pathogens by white blood cells (WBCs), which work as soldiers. WBCs reach the infectious site and kill the invading pathogens. The assessment of WBC activity and function is important in various diseases such as cancer, HIV, and autoimmune disorders; hence their separation is essential. The present study describes a method for WBC separation using the inertial microfluidic technique. A simple spiral microfluidic device with one inlet and three outlets is constructed here for WBC separation. The device functions on a diluted blood sample. Only 2 finger-pricked droplets of blood (~20 µl) are required to prepare the minute volume of a diluted blood sample. A syringe pump is used to infuse the sample into the channel reservoir. The microdevice takes less than 22 s for WBC separation. We report WBC separation efficiency of nearly 90% with 92% RBC rejection ratio. In addition to WBC separation, the spiral microdevice is capable of blood group testing.

Sanjay Mane, Vadiraj Hemadri, Sunil Bhand, Siddhartha Tripathi
Effect of Arterial Flow on Heat Transfer During Magnetic Hyperthermia Application

This paper investigates the effects of location arterial flow on heat transfer during hyperthermia applications. A three-dimensional tumor model consisting of a blood vessel (artery) is modeled and simulated for magnetic hyperthermia physics. The location of the blood vessel (artery) with respect to the tumor is altered in the tumor models and it passes through different positions from the tumor center. The size (diameter) of the artery is 4 mm, and the tumor size is 10 mm. The different artery positions x = 3, 6, 9, and 12 mm from the tumor center are considered in the physical models. Results show that the position of the artery plays a crucial role in heat dissipation from the tumor volume during magnetic hyperthermia. The therapeutic temperature in the tumor tissue decreases when an artery is closer to the tumor center. This is due to the higher heat transfer effect induced by arterial blood flow. However, when the artery is located at the periphery or away from the tumor, higher temperature is induced in the tumor volume during magnetic hyperthermia in comparison to the cases when the artery is located deep inside the tumor volume.

Subeg Singh, Neeraj Kumar
Flow Separation and Pressure Drop Analysis for Blood Flow in Symmetric Stenosed Arteries of Various Shapes

The past two decades witnessed that the symmetric/asymmetric stenosed arteries are an active area of research as it causes numerous arterial diseases such as thrombosis and atherosclerosis, which lead to human death; hence, they need therapeutic attention. Much research has been reported concerning the shape of the stenosis as the elliptical one, but several medical data available in the literature suggest that the stenotic form is of no particular kind. Thus, the present work aims to numerically investigate the severity of a symmetric stenotic region for four different stenotic shapes (plug, triangular, trapezoidal, and elliptical) in terms of the leading pressure drop noted in the narrowed artery. The present work has been carried out for a wide range of Reynolds numbers (30–650) and % area stenosis (60.9–93.8) at stenotic length, β = 2. The new extensive results have been reported regarding the flow characteristics, separated flow zones, Euler number, etc. The separated zones, leading to the propagation of the static blood flow region, are a vital function of Reynolds number and % area stenosis for a fixed stenotic length. Based on the pressure drop analysis and separation zones, it has been noted that the plug shape is the most severe compared to other investigated ones. The triangular shape is seen to be the least severe in terms of causing the pronounced separated zones and pressure drop in the vicinity of the stenosis.

Anamika Maurya, Janani Srree Murallidharan, Atul Sharma
Comparative Study of Uniform and Pulsatile Blood Flow Through Single Stenosed Carotid Artery

Symmetric occlusion with the range of 20–70% reduction in diameter of carotid artery is numerically investigated. Computations have been performed for both steady and pulsatile inlet velocities with the average Reynolds number of 400. Comparison has been made between steady and unsteady flow based on the time-averaged quantities like WSS, reattachment point, etc. The effect of pulsatile inlet velocity is observed in terms of WSS transient behaviour. OSI is monitored to look for the regions favourable in the new plaque formation. Study shows that the result outcomes are realistic and superior when the inlet is employed with a pulsatile flow instead of a steady inlet. Flow behaviour found to be very sensitive to inlet pulse, and associated rapid changes in the WSS might rupture plaque and cause blood clots. OSI distribution shows that the region downstream of stenosis is more prone to new plaque formation.

Swapnil Rajmane, Shaligram Tiwari
Image-Based Retinal Haemodynamics Simulation of Healthy and Pathological Retinal Vasculature

The current study aims to develop a comprehensive computational framework for quantitatively investigating haemodynamics in retinal arterial and venous networks. Two different pathological conditions, diabetic retinopathy and hypertension, have been considered, and the retinal haemodynamics change due to these pathologies has been investigated. Further, the comparison has been made with the healthy retinal vasculature. The retinal vascular tree has been extracted from the fundus images. The blood flow through the vasculature has been simulated, keeping into account the Fåhraeus–Lindqvist effect to incorporate the viscosity changes. Simulated results reveal that the blood flow velocity in arteries and veins decreases with the increase in the radial distance for all the cases. Further, higher average blood velocity and wall shear stress (WSS) are observed in the retinal network of diabetic and hypertension cases compared to the healthy ones. The current numerical model will help delineate the effect of structural changes in the retinal vasculature due to different pathological conditions on the retinal haemodynamics, which may be used as a helpful prognosis tool by ophthalmologists.

Shivam Gupta, Ajay Bhandari
Numerical Study on the Effect of Exercise on Various Configurations of Stenosis in Coronary Artery

One of the primary factors in adult fatalities is coronary artery disease. Hence, the study on the effect of stenosis position and number of stenoses becomes necessary to predict the susceptibility of formation of another stenosis and predict atherosclerotic plaque rupture. The probability of plaque rupture increases under exertion; hence, the current study uses two different pulse rates (75 BPM for the rest condition and 120 BPM for the exercise condition). Higher time-averaged wall shear stress (TAWSS) values are observed in case of double stenoses even at rest conditions. A substantial increase in peak TAWSS value is observed under exercise conditions compared to rest conditions. A downstream shift in oscillatory shear index (OSI) region is observed under exercise conditions for all cases, whereas a significant reduction in OSI region is observed in the case of proximal stenosis.

Siddharth D. Sharma, Piru Mohan Khan, Suman Chakraborty, Somnath Roy
Effect of Aging on Passive Drug Diffusion Through Human Skin

In the present work, a comparative study of the passive diffusion of a drug through the intercellular (ICR) and sweat duct (SDR) routes of human skin has been performed. We have tested trans-cinnamic acid and caffeine as drugs, as those are the most commonly available compounds. The effect of aging on transdermal drug diffusion has been considered by performing the above analysis for young age (< 40 years) and old age (> 60 years). A mathematical model based on Fick’s law is adopted to understand drug diffusion through various layers. Each of the routes is described by a compartment model along with the donor and receiver compartments at the top and bottom, respectively. Code is validated by comparing present results with the published experimental findings. For both tested drugs, it is found that the intercellular route provides a faster route of drug delivery as compared to the sweat duct route. It is also found that the amount of drug diffusion increases upon the aging of human skin.

Aditya Ranjan, Vijay S. Duryodhan, Nagesh D. Patil
Computational Investigation on the Empirical Relation of Murray’s Law

The human circulatory system is complex, and about one-sixth of the resting metabolic rate is consumed for keeping the blood flowing through the system. It consists of geometrical complications such as tapering, branching, channel bifurcations and curvatures. For minimizing the biological work accounting for the blood flow at the bifurcations, Murray’s law was formulated by Cecil D. Murray. The work done in overcoming the viscous drag and the maintenance of the vessel is considered for deriving the empirical relation of Murray’s law. The empirical relation states that the volumetric flow rate is proportional to the cube of the vessel radius. Here, in this study, we have computationally investigated the above stated empirical relation.

Mudrika Singhal, Raghvendra Gupta
Investigation of Impulse Jet Dispersion Mechanism of Needle-Free Drug Delivery Device

Impulse jet injector creates a high-speed liquid microjet through a small orifice that is used for drug injection into the skin. A requisite amount of dosage is administered at a disseminable depth into the skin sample. One of the key aspects of dispersion investigations is to study the flow mechanics of jet propagation inside the target. The injection of the drug into soft materials like polyacrylamide gel slabs is examined in order to understand the process for drug dispersion and uptake. High-speed imaging is used to capture the rapid dynamics of the fluorescent liquid injected into the ballistic polyacrylamide gel slab. A 2D numerical simulation is performed to confirm the jet impact pressure and velocity, and it is found to be in good agreement with experimental results. Understanding physics of jet penetration through polyacrylamide gels allows one to deduce jet injection into skin targets. The findings demonstrate that drug distribution into the target was effective.

Priyanka Hankare, Sanjeev Manjhi, Viren Menezes
Analysis of 2D Human Airway in Laminar and Turbulent Flow Model

In this article, an airflow study of a two-dimensional human airway model is performed using computational fluid dynamics (CFD). The human respiratory system is one of the important parts of the human body where CFD is used to understand the physics of flow, diagnosis, prognosis, and treatment of respiratory diseases. The function of the human respiratory system is to deliver oxygen between the atmosphere and the lungs and remove carbon dioxide. Airflow and particle deposition in the human respiratory tract provide important information for clinical purposes (regional ventilation) and inhalation treatment. In this article, a sixth-generation two-dimensional airflow characteristic of the human respiratory tract is simulated using commercial CFD software. Three different inspiratory flow rates of 10 L/min (normal respiration), 45 L/min (moderately rapid respiration), and 60 L/min (rapid respiration) are considered to see the effects of flow rates. Velocity and pressure contours are calculated to understand the flow physics of the human respiratory system.

Vivek Kumar Srivastava, Aman Raj Anand
Effects of Stenosis Profile on Hemodynamic and Mass Transport in Axisymmetric Geometries: A Numerical Study

In this study, irregular stenosis profile is considered, with its throat area being varied into three different configurations. Ideal geometries are viable for numerically analyzing hemodynamics under various stenosis severities. Numerical work has been carried out on these stenosis profiles under pulsatile flow conditions using open-source software OpenFOAM. The irregular stenosis profile highly influences wall shear stress and its variations. Significant variations in the amplitude of the WSS profile are observed. These stenosis profiles are liable for higher chances of rupture. Mild stenosis further promotes the aggregation of plaque deposits, which the magnitude of WSS fluctuations can predict. The severity of the stenosis has strongly affected mass transfer near the arterial wall by dominating concentration transport by convection into the lumen region. Convection dominated region is strongly limited to upstream of throat section, predominantly for severe stenosis configurations. Hence, actual representation of the stenosis profile with surface irregularity elucidates hemodynamic and mass transfer phenomenon for a better understanding of diseased condition.

Ankani Sunil Varma, K. Arul Prakash
Experimental and Numerical Study of Flow Through Ventilator Splitter

Mechanical ventilation is a technique in which the air and oxygen mixture is pumped into the lungs of patients who have low levels of oxygen and are unable to breathe on their own. During emergencies such as an outbreak like COVID-19, hospitals run short of ventilator devices to meet the growing number of patients who require ventilator support. In such cases, a single ventilator device shall be used to ventilate multiple patients using a flow splitter. This study aims to analyse the hydrodynamics of flow through various splitters for two patients having the same compliance and requiring equal flow rates. For the analysis a 3D Y-Splitter having split angle over a range of 30–180° is designed with an inlet diameter of 21.8 mm splitting into two exit arms each of 19 mm based on the ventilator dimensions available at Meenakshi Hospital, Thanjavur. A transient 3D models are simulated for a range of inlet mass flow rates in ANSYS 2019 R1, and the best splitter with equal outlet mass flow rate is identified. The results are validated experimentally under similar flow conditions.

Aniruddh Mukunth, Raj Shree Rajagopalan, Naren Rajan Parlikkad
Bioconvective MHD Flow of Micropolar Nanofluid Over a Stretching Sheet Due to Gyrotactic Microorganisms with Internal Heat Generation/Absorption and Chemical Reaction

The present work deals with the study of bioconvective MHD flow of micropolar nanofluid containing gyrotactic microorganisms along with chemical reaction over a stretching sheet. Nonuniform heat source/sink and viscous dissipation effects are also considered. The chemical reaction phenomenon reduces the nanoparticle concentration and enhances the mass diffusion rate on the sheet. The nonlinear coupled system of PDEs is converted into nonlinear system of ODEs by using a similarity transformation, and the transformed equations are solved by using MATLAB bvp4c solver. The skin friction coefficient, the microrotation parameter, the Nusselt number, the Sherwood number, and the motile density number are numerically computed and presented. The effects of the pertinent physical parameters on the velocity, angular velocity, temperature, nanoparticle concentration, and motile density of microorganisms are inspected. The present results are relevant in improving the performance of microbial fuel cells and heat transfer devices.

P. Vimala, R. Dhivyalakshmi

Machine Learning in Fluid Mechanics

Application of Machine Learning for Forced Plume in Linearly Stratified Medium

Direct numerical simulation (DNS) is very accurate; however, the computational cost increases significantly with the increase in Reynolds number. On the other hand, we have the Reynolds-averaged Navier–Stokes (RANS) method for simulating turbulent flows, which needs less computational power. Turbulence models based on linear eddy viscosity models (LEVM) in the RANS method, which use a linear stress–strain rate relationship for modeling the Reynolds stress tensor, do not perform well for complex flows (Shih et al. in Comput Methods Appl Mech Eng 125:287–302, 1995). In this work, we intend to study the performance of nonlinear eddy viscosity model (NLEVM) hypothesis for turbulent forced plumes in a linearly stratified environment and modify the standard RANS model coefficients obtained from machine learning. The general eddy viscosity hypothesis supported by the closure coefficients generated from the tensor basis neural network (TBNN) is used to develop TBNN-based K-ϵ model. The aforementioned model is used to evaluate the plume’s mean velocity profile, and maximum height reached. The comparison between standard LEVM, NLEVM, and the experimental results indicates a significant improvement in the maximum height achieved, and a good improvement in the mean velocity profile.

Manthan Mahajan, Nitin Kumar, Deep Shikha, Vamsi K. Chalamalla, Sawan S. Sinha
Comparative Study of Future State Predictions of Unsteady Multiphase Flows Using DMD and Deep Learning

Flow across an array of solid obstructions is a common phenomenon observed in many applications such as multiphase flows, heat exchangers, and environmental flows. In this work, we aim to train deep learning models and to predict the time evolution of unsteady flow fields in a domain of randomly arranged 2D cylinders at Reynolds number 50. Two different approaches are used and compared in this paper, dynamic mode decomposition (DMD) which is a dimensionality-reduction algorithm based on singular value decomposition (SVD) and long short-term memory (LSTM) neural networks. In both cases, the model is trained on the first 165 time steps and then is tested on predicting the next 300 time steps. Two flow fields with different spectral characteristics are used to compare the performance of the two techniques. The LSTM architecture owing to its ability to learn nonlinear dynamics performs better than the DMD algorithm in the case with more temporal time scales present.

Neil Ashwin Raj, Danesh Tafti, Nikhil Muralidhar, Anuj Karpatne
Deep Learning Approach to Predict Remaining Useful Life of Axial Piston Pump

In the hydraulic machines like hydraulic pump, while in use, many faults start to appear in these machines resulting in the undesirable output. One of such parameters is the leakage fault, which is very common in pumps and motors. In pumps, it has been observed that over a period of time with increase in wear, leakage also increases. This relationship between the wear and leakage value is utilized here using the NARX NN to estimate the RUL of the pump. In this work, the different training algorithm has been used in order to train the NARX NN, and the models that has been trained are used to estimate the remaining useful life (RUL) of an axial pump that is being used to control the hydraulic system of sheet metal casting process. Results of the model are promising.

Md Adil, Pratik Punj
Machine Learning-Assisted Modeling of Pressure Hessian Tensor

Velocity gradient dynamics play a pivotal role in understanding various nonlinear phenomena in turbulent flows. In the evolution of velocity gradient dynamics, the pressure Hessian and the viscous Laplacian are two mathematically unclosed terms which need separate modeling. The current study models the pressure Hessian term using the tensor basis neural network (TBNN). The network is trained on direct numerical simulation (DNS) data of stationary incompressible turbulence conditioned on local flow topologies. We compare the topology-based TBNN model performance with the DNS results as well as with the unconditioned (raw) TBNN model. The model results are evaluated in terms of the strain rate and the pressure Hessian eigenvector alignments. The model captures some of the essential alignment features of the DNS results.

Deep Shikha, Sawan S. Sinha
Fluid Mechanics and Fluid Power, Volume 4
Krishna Mohan Singh
Sushanta Dutta
Sudhakar Subudhi
Nikhil Kumar Singh
Copyright Year
Springer Nature Singapore
Electronic ISBN
Print ISBN

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