Numerical simulation of the hydrodynamics of self-propelled fish swimming

Based on a novel method of force analysis, the thrust and drag forces of self-propelled fish are redefined, and the difficulty in distinguish the thrust and drag in fish swimming is overcome. Then, an adaptive ghost-cell immersed boundary method is used to simulate the 2D self-propelled carangiform swimming. Simulation cases are carried out for Reynolds number in the rang of 309 ≥ Re ≥ 14581 (viscous flow) and Re = ∞ (inviscid flow). The results show that: (1) The Strouhal number decreases with increasing the Reynolds number. If the Reynolds number tends towards infinite, the Strouhal number approaches 0.25; (2) For all Reynolds number, the main part of the thrust is the pressure component. The viscous part of the drag is larger than the pressure part when Re 3000; (3) The thrust efficiency increases with increasing the Reynolds number and the maximum efficiency is about 70%. The result show that the carangiform swimming rule suit the high Reynolds situation.