Numerical simulation for two-dimensional unsteady moving boundary problems based on IBVCM

The current study mainly focuses on some fundamental parameters that affect the unsteady moving boundary problems. The relationships between the propulsion force and these parameters are analyzed. To numerically simulate fish swimming in this work, the Lattice Boltzmann Method (LBM) is applied to obtain the information of flow field. At the same time, the velocity near the body is corrected via the Immersed Boundary Velocity Correction Method (IBVCM). Here, a twodimensional oscillating fish is studied and the factors affecting the fish swimming, which are investigated in current study, are the shape, frequency, wavelength, and Reynolds number as well. After a series of simulations with different parameters, the correspondly effects on the propulsion force are obtained. Five kinds of shapes are selected for the fish body, and its motion mode is that the centerline of fish oscillates transversally in the form of traveling wave. Moreover, from the perspective of vortex, the vortex distribution is analyzed with a set of locations on the fish tail tip, and therefore the relationship between the dynamics of vortex and fish motion is achieved. The investigation indicates that the propulsion force is different as fish shape changes, and higher frequency, wavelength, or Reynolds number produces higher propulsion force.