抄録
Theoretical and experimental investigations on Salter's absorbing wave maker are presented, which could generate waves under given command signals and could act as an absorber to incoming waves at the same time. The problem is formulated for a semi-infinite channel and solutions are determined with the linear-theory. The equation for the complete absorption of waves is derived. Theoretical transfer function of linear filter is pressented, where the flap of the wave maker is driven by D.C. moter controlled by the signal of hydrodynamic force acting on the flap. In order to verify this theory, the following experiments are carried out in a channel of 6m length: (a) measurements of the reflected waves when the movement of the flap is restrained, (b) measurements of the reflected waves when the wave maker is driven as an absorber, (c) measurements of surface elevations in the channel for two cases in which the wave maker acts as an usual one and an absorbing one at one end of the channel and the rigid wall at the other end. From those experiments, it is confirmed that an absorbing wave maker studied here has excellent property compared with an usual wave maker. The reflected wave coefficient attains to 8% by this wave maker at the optimum frequency. In conclusion, a system of this type would be very useful for the improvement of the experimental accuracy in a short tank.
