Numerical simulation of the hydrodynamics of self-propelled fish swimming

Based on a novel method of force analysis, the thrust anddrag forces of self-propelled fish are redefined, and the difficulty indistinguish the thrust and drag in fish swimming is overcome. Then, anadaptive ghost-cell immersed boundary method is used to simulate the 2Dself-propelled carangiform swimming. Simulation cases are carried out forReynolds number in the rang of 309 \le Re \le 14581 (viscous flow) andRe=\infty (inviscid flow). The results show that: (1) The Strouhal numberdecreases with increasing the Reynolds number. If the Reynolds number tendstowards infinite, the Strouhal number approaches 0.25; (2) For all Reynoldsnumber, the main part of the thrust is the pressure component. The viscouspart of the drag is larger than the pressure part when Re<3000, while therelationship will be reversed when Re>3000; (3) The thrust efficiencyincreases with increasing the Reynolds number and the maximum efficiency isabout 70%. The result show that the carangiform swimming rule suit thehigh Reynolds situation.