Hydrodynamics Analysis Of The Pectoral-Fins In Viscous Flows

The characteristics of fish swimming are fast, efficient, flexible and quiet. So it's important to apply fish swimming mode to the underwater vehicle propelling system instead of the traditional propeller and rudder system. At present, there are many underwater bionic studies focused on body and/or caudal fin (BCF) locomotion. However, many fishes' propulsion systems perform well for both efficient cruising and high maneuverability at low swimming speed by using paired pectoral fins.In this thesis, the pectoral fin is considered as a rigid paddle and the hydrodynamic performance of the rigid paddle is analyzed by the secondly developed FLUENT (CFD code) which is based on Reynolds-Averaged Navier-Stokes equations. Meanwhile, the method of dynamic mesh and post-processing system are also fully used. Firstly, the hydrodynamic performance of the rigid paddle is computed as a two degree of freedom model with a given frequency. Then the result is used to do a comparative analysis with the result of unsteady vortex lattice method and experiment result. Secondly, the parameters are considered such as Reynolds number, wall condition, phase difference and changed amplitude, and it is discussed that the hydrodynamic performance of the rigid paddle moving with two degree of freedom coupling motions. At last, based on the previous calculations, the unsteady hydrodynamic performance of the rigid paddle is calculated and analyzed as a three degree of freedom model. Through the research in this thesis, the conclusion is drawn that the CFD software related RNS solver is feasible to do the hydrodynamic analysis of oscillating-wing propulsion. More detail research should be done on the unique swim mechanism of fish.