Based on the velocity invariability of the shallow water wave and using the shoaling effect, a unique active wave absorber for numerical wave tank is set up. This absorber’s absorption parameter is constant, thereby make its mechanism very simple. When coupled with damping zone, it can achieve a perfect wave absorption effect. By setting different absorption parameters and coupling with a damping zone, 4 ISOPE wave absorption benchmark experiments are performed using this absorber. The results indicate that, by setting shoaling bottom, this absorber has excellent absorbency on deep water waves and limit depth waves, and when coupled with damping zone, it not only can absorb the wide spectrum nonlinear random waves but also shorten the length of the damping zone effectively.
