Faculty Publications
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Item Effects of the Reynolds number on two-dimensional dielectrophoretic motions of a pair of particles under a uniform electric field(Korean Society of Mechanical Engineers, 2016) Kang, S.; Mannoor, M.; Maniyeri, R.This paper presents two-dimensional direct numerical simulations to explore the effect of the Reynolds number on the Dielectrophoretic (DEP) motion of a pair of freely suspended particles in an unbounded viscous fluid under an external uniform electric field. Accordingly, the electric potential is obtained by solving the Maxwell’s equation with a great sudden change in the electric conductivity at the particle-fluid interface and then the Maxwell stress tensor is integrated to determine the DEP force exerted on each particle. The fluid flow and particle movement, on the other hand, are predicted by solving the continuity and Navier-Stokes equations together with the kinetic equations. Numerical simulations are carried out using a finite volume approach, composed of a sharp interface method for the electric potential and a direct-forcing immersed-boundary method for the fluid flow. Through the simulations, it is found that both particles with the same sign of the conductivity revolve and eventually align themselves in a line with the electric field. With different signs, to the contrary, they revolve in the reverse way and eventually become lined up at a right angle with the electric field. The DEP motion also depends significantly on the Reynolds number defined based on the external electric field for all the combinations of the conductivity signs. When the Reynolds number is approximately below Recr ? 0.1, the DEP motion becomes independent of the Reynolds number and thus can be exactly predicted by the no-inertia solver that neglects all the inertial and convective effects. With increasing Reynolds number above the critical number, on the other hand, the particles trace larger trajectories and thus take longer time during their revolution to the eventual in-line alignment. © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.Item Numerical analysis of the buckling and recuperation dynamics of flexible filament using an immersed boundary framework(Elsevier B.V., 2019) Kanchan, M.; Maniyeri, R.The dynamics of flexible filaments in viscous shear flow is of interest to biologists and engineers in a wide variety of applications involving folding and unfolding sequence of long-chain biomolecules like DNA, non-motile sperm and microalgae. It is also helpful in understanding the deformation of natural and synthetic fibers which can be applied in areas such as biotechnology. In the present work, deformation and migration behavior of non-motile unicellular phytoplankton diatoms subjected to viscous shear flow are considered. These unicellular diatoms develop into colonies which are made up of linked chains. The complex fluid-structure interaction is solved by developing a two-dimensional numerical model with an immersed boundary framework. The simulation consists of suspending an elastic filament mimicking a diatom chain in a shear flow at low Reynolds number. The governing continuity and Navier–Stokes equations are solved on a Cartesian grid arranged in a staggered manner. A forcing term is added to the momentum equation that incorporates the presence of flexible filament in the fluid domain. The discretization of the governing equation is based on a finite volume method, and a SIMPLE algorithm is used to compute pressure and velocity. A computer code is developed to perform numerical simulations, and the model is first verified with the deformation study of a tethered flexible filament in uniform fluid flow. Next, the shape deformations for flexible filament placed freely in shear flow are compared with the studies of previous researchers. Further, the present results are validated with Jeffery's equation for particles immersed in shear flow along with classification plot for filament orbit regimes. All of these comparisons provide a reasonable validity for the developed model. The effect of bending rigidity and shear rate on the deformation and migration characteristics is ascertained with the help of parametric studies. A non-dimensional parameter called Viscous Flow Forcing value (VFF) is calculated to quantify the parametric results. An optimum Viscous Flow Forcing value is determined which indicates the transition of filaments exhibiting either a recuperative (regaining original shape past deformation) or non-recuperative (permanently deformed) behavior. The developed model is successful in capturing fluid motion, diatom buckling, shape recurrences and recuperation dynamics of diatom chains subjected to shear flow. Further, the developed computational model can successfully illustrate filament-fluid interaction for a wide variety of similar problems. © 2019 Elsevier Inc.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 Numerical simulation of buckling and asymmetric behavior of flexible filament using temporal second-order immersed boundary method(Emerald Publishing, 2020) Kanchan, M.; Maniyeri, R.Purpose: The purpose of this paper is to perform two-dimensional numerical simulation involving fluid-structure interaction of flexible filament. The filament is tethered to the bottom of a rectangular channel with oscillating fluid flow inlet conditions at low Reynolds number. The simulations are performed using a temporal second-order finite volume-based immersed boundary method (IBM). Further, to understand the relation between different aspect ratios i.e. ratio of filament length to channel height (Len/H) and fixed channel geometry ratio, i.e. ratio of channel height to channel length (H/Lc) on mixing and pumping capabilities. Design/methodology/approach: The discretization of governing continuity and Navier–Stokes equation is done by finite-volume method on a staggered Cartesian grid. SIMPLE algorithm is used to solve fluid velocity and pressure terms. Two cases of oscillatory flow conditions are used with the flexible filament tethered at the center of bottom channel wall. The first case is sinusoidal oscillatory flow with phase shift (SOFPS) and second case is sinusoidal oscillatory flow without phase shift (SOF). The simulation results are validated with filament dynamics studies of previous researchers. Further, parametric analysis is carried to study the effect of filament length (aspect ratio), filament bending rigidity and Reynolds number on the complex deformation and behavior of flexible filament interacting with nearby oscillating fluid motion. Findings: It is found that selection of right filament length and bending rigidity is crucial for fluid mixing scenarios. The phase shift in fluid motion is also found to critically effect filament displacement dynamics, especially for rigid filaments. Aspect ratio, suitable for mixing applications is dependent on channel geometry ratio. Symmetric deformation is observed for filaments subjected to SOFPS condition irrespective of bending rigidity, whereas medium and low rigidity filaments placed in SOF condition show severe asymmetric behavior. Two key findings of this study are: symmetric filament conformity without appreciable bending produces sweeping motion in fluid flow, which is highly suited for mixing application; and asymmetric behavior shown by the filament depicts antiplectic metachronism commonly found in beating cilia. As a result, it is possible to pin point the type of fluid motion governing fluid mixing and fluid pumping. The developed computational model can, thus, successfully demonstrate filament-fluid interaction for a wide variety of similar problems. Originality/value: The present study uses a temporal second-order finite volume-based IBM to examine flexible filament dynamics for various applications such as fluid mixing. Also, it highlights the relationship between channel geometry ratio and filament aspect ratio and its effect on filament sweep patterns. The study further reports the effect of filament displacement dynamics with or without phase shift for inlet oscillating fluid flow condition. © 2019, Emerald Publishing Limited.Item Fluid-Structure Interaction Study and Flowrate Prediction Past a Flexible Membrane Using Immersed Boundary Method and Artificial Neural Network Techniques(American Society of Mechanical Engineers (ASME), 2020) Kanchan, M.; Maniyeri, R.Many microfluidics-based applications involve fluid-structure interaction (FSI) of flexible membranes. Thin flexible membranes are now being widely used for mixing enhancement, particle segregation, flowrate control, drug delivery, etc. The FSI simulations related to these applications are challenging to numerically implement. In this direction, techniques like immersed boundary method (IBM) have been successful. In this study, two-dimensional numerical simulation of flexible membrane fixed at two end points in a rectangular channel subjected to uniform fluid flow is carried out at low Reynolds number using a finite volume based IBM. A staggered Cartesian grid system is used and SIMPLE algorithm is used to solve the governing continuity and Navier-Stokes equations. The developed model is validated using the previous research work and numerical simulations are carried out for different parametric test cases. Different membrane mode shapes are observed due to the complex interplay between the hydrodynamics and structural elastic forces. Since the membrane undergoes deformation with respect to inlet fluid conditions, a variation in flowrate past the flexible structure is confirmed. It is found that, by changing the membrane length, bending rigidity, and its initial position in the channel, flowrate can be controlled. Also, for membranes that are placed at the channel midplane undergoing self-excited oscillations, there exists a critical dimensionless membrane length condition L ? 1.0 that governs this behavior. Finally, an artificial neural network (ANN) model is developed that successfully predicts flowrate in the channel for different membrane parameters. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.Item Numerical simulation and prediction model development of multiple flexible filaments in viscous shear flow using immersed boundary method and artificial neural network techniques(IOP Publishing Ltd custserv@iop.org, 2020) Kanchan, M.; Maniyeri, R.Many chemical and biological systems have applications involving fluid-structure interaction (FSI) of flexible filaments in viscous fluid. The dynamics of single- and multiple-filament interaction are of interest to engineers and biologists working in the area of DNA fragmentation, protein synthesis, polymer segmentation, folding-unfolding analysis of natural and synthetic fibers, etc. To perform numerical simulation of the above-mentioned FSI applications is challenging. In this direction, methods like the immersed boundary method (IBM) have been quite successful. We simulate the dynamics of multiple flexible filaments subjected to planar shear flow at low Reynolds number using the finite volume method-based IBM. The governing continuity and Navier-Stokes equations are solved by the SIMPLE algorithm on a staggered Cartesian grid system. The validation of the developed model is done using previous works. The length of the filament, its bending rigidity and fluid shear rate are taken as parametric variables and numerical simulations are carried out. Viscous flow forcing and fractional contraction terms are incorporated so as to effectively categorize filament motion into various deformation regimes. The effects of tumbling motion on the filament migration and recuperative aspects are studied. The mutual interaction of two filaments placed side by side is thus observed. Finally, an artificial neural network model is developed from the IBM simulation results to predict tumbling counts for different filament parameters. © 2020 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.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 Control force and inertial migration in Poiseuille flow: a computational study(Taylor and Francis Ltd., 2023) Neeraj, M.P.; Maniyeri, R.The present work deals with the development of a numerical model to analyze the effect of control force on a single rigid massive cylindrical particle’s lateral migration in a straight channel. The finite volume immersed boundary method (feedback forcing-based), along with semi-implicit strategy, is incorporated to create a computational model. The control force is applied in the direction against the fluid flow, to control the equilibrium position and drive it to the channel center. The effect of the Reynolds number, particle diameter and density ratio on the control force is studied. From parametric studies, a prediction model is developed for the control force with the Reynolds number, particle diameter and density ratio as inputs. The linear regression methodology in machine learning is utilized to create the prediction model. The predicted values of control force are observed to match those of the simulation results. © 2023 Taylor & Francis Group, LLC.Item Lateral Migration of Variously Shaped Particles: A Computational Study(John Wiley and Sons Inc, 2023) Neeraj, M.P.; Maniyeri, R.The current work deals with the simulation of lateral migration of differently shaped particles in a straight channel through which fluid flows with a Poiseuille pattern of flow. The immersed boundary method based on feedback force is adopted for the current work. The equilibrium positions and migration times for circular, elliptical, rectangular, square, and biconcave particles are studied and presented. The cases of neutral and massive (high ratio of particle density to fluid density) particles are presented, and in both scenarios the biconcave particle attains its equilibrium position closest to the bottom wall and the elliptical particle acquires its equilibrium position closest to the channel center. Also, the migration time is highest for the biconcave particle, whereas it is lowest for the rectangular particle. © 2023 Wiley-VCH GmbH.