A Study on Fluid-Structure Interaction of Swimming Beam Using Immersed Boundary- Lattice Boltzmann Method

摘要

Fluid-structure interaction (FSI) study is of great importance to understand the hydrodynamic coupling of biological swimmers in surrounding environmental domain. Multiple numerical and experimental studies have taken place to capture the behavioral pattern from the environment, explore the physical phenomena and comprehension of dynamics to make contribution in real life applications. In this study, an immersed boundary-lattice Boltzmann method (IB-LBM) for fluid-structure interaction problems is presented. The impact of solid structure on to the surrounding fluid domain is dealt with by immersed boundary method (IBM), where the structure is assumed to be immersed into surrounding fluid and the effect of the immersed boundary are considered by exertion of Lagrangian force onto the surrounding fluid grid points as body force. The flow dynamics is determined by solving discrete lattice Boltzmann equation of a single relaxation time model. The structural dynamics are solved by the finite difference method. For solving the structural dynamics, inextensibility condition was applied. A staggered grid is used in the Lagrangian coordinate system, where tension force is defined on the interfaces (half-grids) and other variables are defined on the nodes. Tension force is calculated at the intermediate steps and used as inextensibility constraint to obtain filament position at the next time step. In the present study, a detailed derivation and corresponding discretization is done for multiple free-swimming cases for a thin flexible filament. The thin flexible filament is actuated by imposing oscillatory heaving and pitching motion at the leading edge with prescribed control parameters. The flow physics of the system is investigated and pressure on the surfaces of the flexible filament is obtained. The results obtained in this study shows consistency with previous publications. The presented computational modelling may be used in future with multiple obstacles in the domain, to investigate the surface pressure variation of the swimming flexible filament and generated data sets may contribute to optimization of control mechanism of the swimmer.