Numerical Simulation of Moving Boundary Problems with Application to Fish Swimming

Abstract

This thesis focuses on the development of a hybrid meshfree-Cartesian grid scheme based on generalized finite difference (GFD) method for simulation of fluid flows involving moving boundary. Results show that the present singular-value decomposition (SVD)-based GFD method is more robust and accurate than the conventional least square (LS)-based GFD scheme. To overcome the problem of numerical instability that comes from clustering of computational nodes, a nodal selection scheme is introduced and applied to flow problems involving close interactions of moving bodies. The present scheme is further developed for problems involving deforming boundaries and coupled fluid-structure interaction (FSI). The latter is accomplished by an implicit iterative scheme. The FSI procedure is validated on a series of sedimentation problems and the migration of a cylinder in shear flow. The full methodology is applied to problems in undulatory-body self propulsion. Simulations of the fish undergoing cyclic/steady swimming and sharp turning manoeuvre at Reynolds number of up to 5000 are performed. Swimming towards a designated target is simulated with the help of a feedback control algorithm.