Experimental Investigation on The Hydrodynamic Properties of the Two-Dimensional Wave Absorber

Abstract

In order to extract the wave power by a floating type wave absorber, an external mechanical system is necessary. In this study, a small DC-generator and a coil spring are used to control the motion of floating body. By changing the electric resistance and the spring constant of coil, arbitrary external forces can be added to the body. The sectional form of the floating body is determined by the theoretical calculation which satisfies the condition of being wave-free on one side under heave mode oscillation. To investigate the hydrodynamic properties of 2-dimensional models of wave absorber with external forces or without them, the following experiments are carried out at the small water tank which was newly built in Osaka University. (1) Measurements of added mass and damping coefficients and radiated waves by forced heave oscillation tests in still water without external forces. (2) Measurements of wave exciting forces, transmitted waves and drifting forces with restrained models in regular waves. (3) Measurements of heave motions, transmitted waves and drifting forces with heave free models in regular waves without external forces. (4) The same measurements as (3) with external forces. The results of experiments are compared with the theoretical calculations by the method of singularity distribution.