Faculty Publications
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Item Numerical study on the dynamics of organism motion under background flow(Association for Computing Machinery acmhelp@acm.org, 2017) Maniyeri, R.; Kang, S.We propose a two-dimensional numerical model to investigate the dynamic behaviour of an organism swimming in a background flow in a channel. In this work, the organism is modeled as a neutrally buoyant one-dimensional elastic filament based on an immersed boundary finite volume method. Further, the organism is modeled using discrete number of immersed boundary points and the Navier-Stokes equations governing the flow are solved on a staggered Cartesian grid system. A driving function is applied which results in a wave travelling along the length of the organism from left to right. It is found that under no background flow, the organism swim in the forward direction (right to left) when the wave travel over the organism is in the opposite direction. It is observed that, under a uniform background flow, a non-motile organism is simply dragged by the flow whereas a motile organism swims backward along the direction of flow. Further, it is seen that a propulsion enhancement is found in the case of organism swimming along the flow direction when the wave travel is in the opposite direction as that of the flow. © 2017 Association for Computing Machinery.Item Numerical Study on the Behavior of an Elastic Capsule in Channel Flow Using Immersed Boundary Method(Springer Science and Business Media Deutschland GmbH, 2020) Maniyeri, R.; Kang, S.The study of motion and dynamic behavior of elastic capsules in Poiseuille flow in a channel has become an interesting topic of research because of the wide range of applications in the field of biomedical engineering. The behavior of an elastic capsule in an externally applied flow is challenging because of the large displacement fluid–elastic structure interaction involved. In this work, we develop a computational model to capture the physics of the motion and behavior of an elastic capsule in Poiseuille flow in a channel using an immersed boundary finite volume method. The circular-shaped capsule is divided into a number of immersed boundary (IB) points. We create elastic links structure between IB points to incorporate tension/compression and bending. The flow is governed by continuity and Navier–Stokes equations which are discretized using staggered grid-based finite volume method. Dirac delta function is used to interpolate between solid (capsule) and fluid grids. Simulations are first carried out to describe the instantaneous position and shape of the capsule at a fixed Reynolds number flow in the channel. It is observed that the initial location has a significant influence in determining the final shape and position of the capsule. Further, through numerical simulations, the position and shapes of circular capsule in center-line motion with different stiffness constants for links are obtained and compared. It is found that lower elastic spring constant together with lower bending stiffness constant leads to larger deformation of the capsule because of less resistance to the flow. Also, the outcome of different Reynolds numbers (Re) on the behavior of the capsule is investigated for the center-line motion. It is noticed that the motion of the capsule retards with the increase in Reynolds number. Also, for higher value of Re, the capsule deforms less. For lower value of Re, the capsule deforms to a large extent. © 2020, Springer Nature Singapore Pte Ltd.Item Dynamics of bacterial flagellum in a channel flow for design of artificial microrobot(American Institute of Physics Inc. subs@aip.org, 2020) Maniyeri, R.; Kang, S.Design of artificial microrobot based on the propulsion behavior of flagellated bacteria has got immense interest in the recent times due its potential in the field of biomedical applications. Such design will depend not only the structural features of the bacterial helical flagellum but also the fluid flow dynamics. Further, the size of the channel and the initial position of the flagellum in the channel under pressure driven fluid flow will also affect the swimming strategy of the flagellum based robot design. With this perspective, numerical study is carried out in this paper by constructing a computational model to investigate the dynamics of helical flagellum of a bacterium under fluid flow in a channel. The problem involves fluid-structure interaction with the structure being highly flexible and the fluid is flowing from inlet to outlet of the channel making the study complex and challenging. Accordingly, an immersed boundary method based numerical model is created in which flagellum is constructed using elastic link network and the flow is modeled using Stokes equations. Numerical simulations are done mainly to see the effect of channel size and the initial location of the flagellum in the channel on the propulsive dynamics of the flagellum. Forward and mean forward swimming speeds of the helical flagellum are computed to present a comparison for each case using the built model. © 2020 Author(s).Item Inertial Migration of Cylindrical Particle in Stepped Channel—A Numerical Study(Springer Science and Business Media Deutschland GmbH, 2022) Neeraj, M.P.; Maniyeri, R.; Kang, S.Inertial migration of solid rigid particle in fluid flow occurs by the virtue of pure mechanical forces and it can play a pivotal role in separation techniques. The present computational study tries to capture the inertial migration dynamics of single rigid neutrally buoyant cylindrical particle in fluid flow which is residing in a stepped (sudden contraction) channel by determining the equilibrium position and migration time. The immersed boundary method based on feedback forcing scheme is used to develop the numerical model. The particle performs both translation and rotation motion according to the fluid flow condition and is modelled as rigid immersed boundary and the governing fluid momentum, and continuity equations are discretized using finite volume method in a staggered grid system and solved using semi-implicit fractional step algorithm. The study is mainly performed for centre and off-centre initial positions and its influence on the equilibrium position and migration time. It is observed that the equilibrium position is dependent on the initial position of release of particle. As initial position shifts from centre of channel, the particle equilibrium position also shifts accordingly. Further, the effect of height and length of step (contraction portion) on lateral migration is explored. The equilibrium position is found to be shifting towards the upper wall with decrease in height of step. However, the change in height of step does not have any significant effect on migration time of particle. It is identified that the increase in length of step reduces the migration time of particle although the equilibrium position remains same. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.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.