Hydrodynamic Analysis Of Submersible Robofish Propulsion

People have developed many Underwater Unmanned Vehicle in order to detect and empolder resources in ocean or get the thalassocracy. Their maneuvering and control systems are made up of several propellers. This system has many disadvantages such as big volume, high consuming of energy, low total efficiency , high noise and vortex. On the other hand , fish have drawn people' s attention because they have abilities of navigating in high speed with long distance, agilely maneuvering in limited space and accelerating or decelerating rapidly. So people have paid their attention on robofish propulsion system which has more advantages than propellers.The study object in this paper is a lunate caudal fin imitating tuna-tail with the mode combined swaying and yawing in uniform flow which is incompressible and inviscid. First, we calculate the hydrodynamic performance of the caudal fin which is considered as a rigid body using surface panel method. Then a detailed analysis is given. In order to imitate tune tail fin better, a flexible fin only in chordwise is considered. Results shows that flexibility can increase the propulsive efficiency and cause small decreases in the average thrust compared with a rigid caudal fin with similar motion. Next , a comparison between the rectangle fin and the lunate fin is given. From this compare , we can know that the lunate fin has higher efficiency than the rectangle fin. It shows the choice of nature.Of course it is almost impossible trying to get the performance only by imitating the shape of fish. Nowadays, this aim is so difficult considering our abilities. But I believe this kind of UUV with robofish propulsion system will swim like fish sooner or later.