Theoretic And Experimental Research On Hydrodynamic Performance Of Biomimetic Pectoral Fin Propulsive System

Mini-bionic Unmanned Underwater Vehicle has many excellent characteristics such as low noise, small resistance, fraudulence, and low cost. In the future, mini-bionic UUV will be used spread in military equipment and ocean developing field. On bionic UUV, the caudal fin is used for propulsion. However, only with the help of pectoral fin, agile maneuver and arbitrary gesture-control can be achieved on bionic UUV. Many fish finish maneuver such as suspension, forward movement and backward movement by motion of pectoral fin. Based on both propulsion mechanism and performance of pectoral fin, the research on maneuverability of bionic UUV is not only theoretically significant but also practically valuable. The investigation on hydrodynamic performance and propulsion mechanism of pectoral fin is done by computational fluid dynamic (short for CFD) method in this thesis.1. The two degree of freedom (short for 2 DoF) motion model is built based on fish pectoral. According to 2 DoF model, flexible deformation mode is proposed. Hydrodynamics are calculated by CFD method. Firstly, propulsion efficiency of pectoral fin is obtained based on rigid body motion principle, which is also used in the study mentioned below. Secondly, the effects of motion parameters on propulsion performance are analyzed, which are optimized later. Then, three dimension flow field is slice to pieces on which vortex contour is drawn. Propulsion mechanics of both rigid and flexible pectoral fins is discussed by the variation of vorticity in one motion period. In the parallel computing, surface grid motion error is eliminated by special node distribution method.2. Three degree of freedom (short for 3 DoF) motion model is built. Then, the parameter about flapping motion is analyzed in order to find the effects on hydrodynamics. Propulsion mechanics is discussed by slices of flow field, which is the same as method used in 2 DoF model. Combining with pressure distribution, the relationship between hydrodynamic curves and wake shedding is analyzed. By separating coupled motions, the contribution of a single degree of freedom motion on hydrodynamic performance is discussed. 3. Both hydrodynamic performance and propulsion mechanics of rigid flapping lift-based wing is researched. The bionic flapping hydrofoil (short for BFH) like a penguin’s is the research model. Hydrodynamic performance of three dimension rigid bionic flapping hydrofoil is analyzed by panel method and CFD method. Effects of motion parameters on hydrodynamic performance are discussed. Then, the vortex variation process is discussed by slices of flow field.4. A bionic pectoral fin experimental propulsion system is developed. A serious of experiments is performed. The experimental results are compared with numerical results. Combining with numerical method, research method on hydrodynamic performance of 2 DoF pectoral fin is improved, which is the basis for development and application of pectoral fin propulsion system in future.The research indicates that CFD method is available to propulsion mechanism investigation and hydrodynamic performance analysis of pectoral fin for various motion models. The theoretical and technical foundation is supplied to design pectoral fin propulsion system and develop highly agile bionic UUV.