Deformable camber-line foil and its applications

Abstract

Foils play important roles in fluid dynamics. Fish uses fins for propulsion and direction control, and these fins are foils. Also the body of the fish itself is a foil to produce strong propulsion force. These foils deform themselves in order to get the best efficiency for propulsion and control. However, foils on the present bio-mimetic underwater fish-like robots are rigid flat plates in most cases, and the body of the bio-mimetic fish is usually a rigid body with a movable tail fin. The author has developed a deformable camber-line foil with a very simple link mechanism without any special actuators such as motors. This mechanism can grasp the flow well and can get the stronger thrust force than the flat plate or rigid foil. This mechanism shows another link mechanism which can deform a straight line into sinusoidal cyclic curve like a snake. However, sinusoidal cyclic curve with time delay is not possible because of the link mechanism. This deformable camber-line foil can not only be applied on bio-mimetic underwater robots, but also have very wide applications such as sail of yacht or rudder of ship. Controllable pitch propeller (CPP) including ship's propeller and wind/current power generator's rotor may be candidates of this application by keeping the pitch (=moving distance per revolution) the same at any radius. The details of the mechanism will be shown in this paper.