A Fundamental Study on the Wave Absorber

Abstract

It has been shown theoretically by Bessho that it is possible to absorb a train of regular waves passed a floating body if its motion is properly controlled. It has also been shown experimentally by J. H. Milgram that in a specified case, the “perfect wave absorption” could be realized.In this paper, the authors rearrange Bessho's theory and show that when an incident wave is diffracted by a fixed body, the height of symmetric wave system and asymmetric wave system which are fundamental components of the reflected and the transmitted waves is exactly one half of the height of the incident wave, and show that this relation is valid independent of the form of the body. They also show that this relation holds in the case when the body is allowed to move provided the body is of symmetric.Making use of these relation, the authors show theoretically and experimentally that it is possible to absorb completely the energy of an incident wave by actively controlling the motion of a floating body.They also show that at the “wave absorption point” at which no reflected and transmitted wave exist, the work done by the mechanism which activated the body is negative and is equal to the energy of the incident wave.