Numercial Simulations Of Self-propelled Anguilliform Swimming Based On The Local DFD

Self-propelled anguilliform swimming in the viscous fluid has been investigated by using the local domain-free-discretization (DFD) method. Given the deformation of the fish body in its own reference frame, the translational and rotational motions of the body governed by Newton's law are solved together with the surrounding flow field governed by the incompressible Navier-Stokes equations. In the local DFD method, the discrete form of partial differential equations at an interior point may involve some points outside the solution domain. The flow variables'values at the exterior dependent points are updated at each time-step by proper extrapolation along the normal direction to wall in conjunction with boundary conditions and the simplified momentum equation in the vicinity of wall. Using the local DFD method, flow equations can be solved on a fixed grid for moving boundary problems, and there is no need to update the grid at each time-step. Some critical issues associated with grid updating can be removed. Compared to the classical methods, this method allows the simulation of flows around multi-bodies undergoing large deformations and arbitrary movements in a straightforward manner.The numerical experiments consist of three parts: (1) Vortex-induced vibration of a circular cylinder with virtual damp. This verifies the reliability of the local DFD method for fluid-solid interaction problems; (2) Self-propelled anguilliform swimming of a fish-like body. The kinematics and dynamics of the fish-like body and characteristics of the surrounding flow field have been obtained. Comparisons between the computed results and the referenced data further conform the reliability of local DFD for simulating complex fluid-solid interactions (3) Self-propelled anguilliform swimming of multiple fish-like bodies. A reasonable analysis is given for the obtained results.The applications to self-propelled swimming simulations underline the potential of the local DFD method as a powerful simulation tool for bio-fluid problems.