This study deals with the dynamic absorption of water waves. We focus here our attention on the case of a simple devce, a 2D piston, in order to exploit the well-known expressions of the potential as far as possible in the design of new absorption laws. We consider a semi-infinite two dimensional wave tank closed by a mobile vertical plane. An unsteady wave train generated at infinity impiges on this plate. The problem of the dynamic absorption consists in finding, in real time, the velocity to be given to the plate so that the radiated and the reflected wave trains should cancel each other. We propose here to derive this velocity from the forces measured on the plate. We first derive a frequency dependant transfer function between the optimal velocity of... |