The Theoretical Prediction And Experimental Research On The Hydrodynamic Performance Of Biomimetic Propulsion

In recent years, fish and ocean mammal have drawn people's attention for their nicer propulsion and maneuvering performance. They have abilities of navigating in high speed with long distance, agilely maneuvering in limited space, and accelerating or decelerating rapidly. The work is to find some mechanics which make some creatures have excellent swimming skill. From the hard work we have known the mechanics of high speed of some fish. The fish can use their characteristics of tails to get the high thrust force. Also they can control their wake to produce the anti-Karman vortex street which is the reason of optimal propulsion.Simulating the tail swing manner of Tunny, a robotic fish model is made. Speed, resistance and thrust at mooring condition of the robotic fish are tested by experiment. the mechanics of highly active propulsion is also known which gives the theoretical basis of fin and its mathematical model.Numerical model of robotic fish propulsion's tail-fin locomotion is established, and tail-fin's mean thrust performance curve and mean efficiency curve is calculated with boundary method when the tail-fin and tail-handle swing with different phase angle, and the correlative curve between swing frequency and amplitude of and tail-fin thrust when the tail-fin and tail-handle swing with the same phase angle. The results of calculation are used as the basis of research of new propulsion. To avoid the swing of fore body of robotic fish with single tail-fin, a kind of robotic fish with double tail-fin is designed and is used in SWATH. The experimental platform of double tail-fin propulsion is produced and the experimental research of the double tail-fin propulsion is made in a pond. As a result, the double tail-fin propulsion as a new type propulsion not only can solve the shakable problem of the single tail-fin robotic fish when it's swimming, but also has excellent propulsive efficiency and maneuverability. The CFD software FLUENT was used to calculate the unsteady flow characteristic of the swinging tail-fin. According to the different flow characteristic between the single tail-fin and the double tail-fin, the writer analyzes the mutual interferential problem during the swing process of the double tail-fin and the calculated result is coincident with the experimental research.