Research On Propulsive Characteristics For Three-dimensional Caudal Fin And Pectoral Fin

In nowadays, the research of the small underwater vehicle is a hotspot along with exploring and utilizing of the deep sea resources. The swimming modes of fish have many characters which are high speed, more efficiency, maneuverability, low noise and so on. It is very important to be guide for the small underwater vehicle.The swimming modes of fish can be divided into two types: body or caudal fin locomotion and median or paired fin locomotion, which are numerically simulated by the CFD software in this paper. The hydrodynamic performance and flow field of different conditions are presented. Firstly, the unsteady flow field of three-dimensional caudal fin with chordwise flexibility is conducted. The effects of various parameters which are chordwise flexibility coefficient, power exponent, and chordwise flexibility length on the hydrodynamics performance are studied. In addition the effect of chordwise and spanwise which are both flexible on the hydrodynamics performance are focused. The hydrodynamic performance of the phase angle between chordwise and spanwise, spanwise flexibility coefficient and spanwise flexibility length when phase angle is 90 degree and 0 degree are computed. Secondly, three-dimensional pectoral fin model is established. And then the rigid pectoral fin with single-degree-of-freedom motion and two-degree-of freedom motion, also flexible pectoral fin with flapping motion are computed, respectively. The varied hydrodynamic coefficients are discussed. At last, the whole fish model including fish body, caudal fin and pectoral fin which prototype is a blue fin tunny is established the whole model. The structure of flow field owing to the motions of caudal fin and pectoral fin are discussed.Through the research in this paper, the propulsive performances of the flexible caudal fin which chordwise and spanwise are both flexible are better than caudal fin which only chordwise are flexible. In addition, when the phase angle between chorwise and spanwise is 90 degree, can achieve the best the propulsive performance.Three-dimensional pectoral fin computational model is established, which can discuss hydrodynamics characteristics with different motions based on. Subsequently, the model of fish body, caudal fin and pectoral fin is established which is can be the guide for the design of small underwater vehicle.