Faculty Publications
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Item Numerical simulation of flow in a wavy wall microchannel using immersed boundary method(Bentham Science Publishers, 2020) Kanchan, M.; Maniyeri, R.Background: Fluid flow in microchannels is restricted to low Reynolds number regimes and hence inducing chaotic mixing in such devices is a major challenge. Over the years, the Immersed Boundary Method (IBM) has proved its ability in handling complex fluid-structure interaction prob-lems. Objectives: Inspired by recent patents in microchannel mixing devices, we study passive mixing effects by performing two-dimensional numerical simulations of wavy wall in channel flow using IBM. Methods: The continuity and Navier-Stokes equations governing the flow are solved by fractional step based finite volume method on a staggered Cartesian grid system. Fluid variables are described by Eulerian coordinates and solid boundary by Lagrangian coordinates. A four-point Dirac delta function is used to couple both the coordinate variables. A momentum forcing term is added to the governing equation in order to impose the no-slip boundary condition between the wavy wall and fluid interface. Results: Parametric study is carried out to analyze the fluid flow characteristics by varying amplitude and wavelength of wavy wall configurations for different Reynolds number. Conclusion: Configurations of wavy wall microchannels having a higher amplitude and lower wavelengths show optimum results for mixing applications. © 2020 Bentham Science Publishers.Item Comparative computational appraisal of supercritical CO2-based natural circulation loop: effect of heat-exchanger and isothermal wall(Springer Science and Business Media B.V., 2020) Thimmaiah, S.; Wahidi, T.; Yadav, A.; Mahalingam, A.Natural circulation loop (NCL) is a geometrically simple heat transfer device in which fluid flow occurs due to density gradient of loop fluid, induced by the temperature difference between the source and the sink. NCL has an inherent problem of instability caused by the combined effect of buoyancy, friction and inertia forces at varying operating conditions, and hence it requires an elegant solution of instability. The primary objective of the present work is to do a comparative study on the dynamic performance between two different configurations of NCL based on supercritical CO2, i.e. (i) NCL with isothermal heater and a cold heat-exchanger (ISO-CHX), and (ii) NCL with hot and cold heat-exchangers (HHX-CHX). To explore these NCLs, two-dimensional transient computational fluid dynamics studies have been carried out on the stability of supercritical CO2-based natural circulation loop. Results are obtained for different operating pressures and temperatures in the form of mass flow rate and velocity variation with respect to time. Results show the higher instabilities in both side heat-exchanger loop than an isothermal heater with heat-exchanger loop. At a lower rate of heat input at source in the HHX-CHX loop, the mass flow is bidirectional, whereas it is unidirectional in the ISO-CHX loop at all level of heat input. It is also observed that as pressure increases, flow instability also increases. Obtained results are validated with the published experimental and numerical data and found in good agreement. © 2020, Akadémiai Kiadó, Budapest, Hungary.Item A proposal for a correlation to calculate pressure drop in reticulated porous media with the help of numerical investigation of pressure drop in ideal & randomized reticulated structures(Elsevier Ltd, 2021) Rambabu, S.; Kartik Sriram, K.; Chamarthy, S.; Parthasarathy, P.; Velamati, V.This paper presents a numerical investigation to estimate pressure drop in fluid flow through reticulated ideal and randomized porous structures. The 3D open-cell foam geometries are constructed using an in-house code along with the use of visualization tool kit (VTK) libraries. In this study, the ideal and randomized Kelvin structures with different porosities and pore densities are generated. These structures have been used to perform direct pore level simulations (DPLS) with the aid of a commercial CFD software. The simulation results are used to acquire the pressure drop across the structures. The pressure drop variation with respect to pore density, porosity, specific surface area, and randomization are analyzed and a pressure drop correlation for reticulated structures with new values of viscous and inertial coefficients is proposed. The validity of the proposed correlation is compared against the experimental and numerical data of the real structures that are available in the literature. © 2021 Elsevier LtdItem Comparative studies on air, water and nanofluids based Rayleigh–Benard natural convection using lattice Boltzmann method: CFD and exergy analysis(Springer Science and Business Media B.V., 2022) Karki, P.; Arumuga Perumal, D.A.; Yadav, A.K.The present study incorporates laminar natural convection and entropy generation in Rayleigh–Benard (R–B) convection with air, water and alumina–water nanofluid as working fluids. The fluid flow and energy equations are solved using D2Q9 and D2Q5 LBM models, respectively. The effects of Rayleigh numbers (Ra = 5 × 103, 104, 105) and volume fractions (? = 0 to 0.08) of nanoparticles on heat transfer and irreversibility are investigated. Results show that the heat transfer evaluated based on Nusselt number is enhanced due to addition of nanoparticles in the base fluid. The maximum enhancement in Nusselt number is found to be 13.93% at Ra = 105 with 8% of nanoparticle in base fluid. The various irreversibilities considered in this study are thermal, fluid flow and total irreversibility, where fluid flow and total irreversibilities in the study depend on irreversibility ratio. The irreversibility ratios taken into account are 10–2, 10–3, 10–4 and 10–5. One facet of study shows the deviation in onset of critical Rayleigh number for air is 1.58%. The other facet indicates dimensionless heat transfer, fluid flow and total irreversibility decrease with the increase in volume fraction of nanoparticles in the base fluid. The analyzed results of irreversibilities are presented in normalized form. In addition, dimensionless entropy generation maps and Bejan number contours are also plotted. © 2021, Akadémiai Kiadó, Budapest, Hungary.Item Modeling rigid filament interaction under oscillatory flow using immersed boundary method(Elsevier Ltd, 2022) Eldoe, J.B.; Kanchan, M.; Maniyeri, R.The thread-like biological filament structures can enhance many processes such as fluid transport, locomotion, defence against foreign bodies etc. Researchers have tried to mimic these filament movements to improve fluid transport, mixing, drug delivery for microfluidic applications. These biological filaments can be modelled as slender rigid filaments which can be either active or passive. Active filaments move on their own thus causing a disruption in the fluid domain in close vicinity while passive filaments undergo motion depending upon the fluid flow past them. The dynamics of both active and passive filaments in low Reynolds number flow has immense research potential. In the case of passive filament, the nature of the incoming flow field is an important factor that affects the flow physics around the filament. This paper studies the flow dynamics of vertical and inclined passive rigid filaments in an oscillatory flow. The effect of change in flow conditions is studied by varying the Reynolds and Strouhal numbers. The simulation involves fluid-structure interaction which is implemented with the help of continuous forcing based immersed boundary (IB) method using finite volume discretization. This is a preliminary work towards modelling active filaments under different fluid flow conditions in channel in the near future. © 2022Item Numerical modeling of straight and helical elastic rods under fluid flow using immersed boundary method(Elsevier Ltd, 2022) Maniyeri, R.This paper presents a three-dimensional computational model built using immersed boundary finite volume method to explore the dynamics of straight and helical elastic rods rotating under an applied fluid flow in a channel. Numerical simulations are done for low and high rotational frequencies of a base motor attached at one fixed end of the rods. Simulations reveal that under low rotational frequency, a straight rod (bend at free end) always performs stable twirling motion and eventually attains straight state (mechanical equilibrium) under an applied fluid flow. But on the other hand, for the same conditions a helical rod always keeps its helical shape during interaction with fluid and never attains stable straight state. For the case of high rotational frequency, the straight rod executes whirling motion in which it attains helical shape during all the time. Whirling motion is also observed for helical rod under high rotational frequency. For similar conditions, the instantaneous shapes obtained by straight and helical rods are different which indicates that the initial configuration of the rod as well as rotational frequency have significant impact in deciding the dynamics of the elastic rod under fluid flow. In the biological realm, these elastic rods represent flagellum of monotrichous bacteria which helps for propulsion in fluid. Hence, the present simulation results will help to develop efficient bacteria inspired artificial microrobot for biomedical applications. © 2022Item Analysis of Fluid Flows in Bounded Domain with Particular Shape of a Cavity using Lattice Boltzmann Method(Bentham Science Publishers, 2023) Shetty, V.V.; Balashanker, K.; Arumuga Perumal, A.P.; Patel, V.U.The present work numerically models the incompressible, continuous phase, viscous flow of Newtonian fluid flow in a bounded domain of two-dimensional cavity that is driven by walls and contains grooves in the shape of squares on the lower wall. With the help of the mesoscopic lattice Boltzmann method (LBM) and D2Q9 square lattice model, simulation results are found stable and reliable. The flow physics of the problem by varying Reynolds number, the height and quantity of lower wall grooves, and other fluid flow characteristics within the bounded domain are studied in detail. It is seen that the effects of the groove heights and wavelengths on the fluid flow are structured within the bounded domain. The study is performed from low Re = 100 to high Re = 3200, with minimum two and maximum four-wavelength grooves evaluated on the bottom surface, each having a height of low 0.25 and high 0.75. Additionally, a thorough discussion of complicated vortex dynamics is provided regarding the input parameters and geometry. Objective: The current study aims to use mesoscopic LBM to analyze incompressible viscous fluid flows on complex geometries other than rectangular shapes. Methods: Mesoscopic approach of kinetic theory-based Lattice Boltzmann method (LBM) is implemented in the current work. The popular Single Relaxation Time Lattice Boltzmann method with D2Q9 square lattice model and second-order accurate boundary condition is adopted for the current study. Results: The numerical approach of LBM is used to simulate fluid flows in a 2D bounded domain with grooved bottom surfaces. The influence of different factors, such as the height of bottom-wall surface grooves, flow Reynolds number, and wavelength of these grooves on flow patterns, is then investigated. Conclusion: The numerical study of the bounded domain is considered, and the Reynolds number is varied from 100 to 3200, with two and four-wavelength grooves evaluated on the bottom surface, each having a height of 0.25 and 0.75. The impacts on the flow pattern both within and slightly above the grooves of the computational findings for different Reynolds numbers, groove heights, and groove wavelengths are evaluated. As the Reynolds number rises, the mixing phenomenon of fluid is shown to flow more quickly in the wall-driven enclosures. © 2023 Bentham Science Publishers.Item Simulation of fluid flow in a lid-driven cavity with different wave lengths corrugated walls using Lattice Boltzmann method(Taiwan Institute of Chemical Engineers, 2023) Fatima, N.; Rajan, I.; Arumuga Perumal, D.A.; Anbalagan, A.; Ahmed, S.A.A.; Gorji, M.R.; Ahmad, Z.Background: The Lid-driven cavity (LDC) flow is an interesting problem in fluid mechanics. The lattice Boltzmann Method (LBM) is used to simulate fluid flow in a LDC with different wave lengths corrugated walls. Methods: The D2Q9 model is used for the 2D bounded domain where the analysis of bottom-bounded wall corrugations on the flow features is analyzed. For validation, a square corrugation along the bottom wall with a driven top wall is considered. A lattice size independence study is performed and the LBM code is substantiated with published results for different values of Reynolds number. The code is then modified by using sinusoidal corrugated walls with different wavelengths along the bottom surface. Significant finding: The streamline patterns, vorticity contours and kinetic energy contours are studied for different Reynolds number. Results shown that the position, number and size of vortices depend on the number of corrugations and value of Reynolds number used. The secondary vortices tend to increase in size as the Reynolds number increase. The kinetic energy contours show maximum energy near the top wall which reduces inside the cavity. © 2023