An effective resonant wave absorber for long regular water waves

Abstract

A new type of resonant wave absorber is proposed to absorb long regular waves more effectively in physical wave flume based on the mechanism of gap resonance. The wave absorber is designed by placing a fixed box in front of the end of a physical wave flume, thereby forming a gap between the box and the end wall. To achieve optimal performance, both resonant and damping conditions for the wave absorber should be matched. The resonant condition requires that the resonant period of the fluid confined in the wave absorber closely mirrors the incident wave period, and the damping condition requires the introduction of appropriate damping into the absorber. The experimental results show that the present short-length resonant wave absorber performs well within a wide range of wave period T ∈ [1.37 s, 3.63 s], which is difficult to be achieved with traditional passive wave absorbers. The reflection coefficient Cr, ratio of wave heights of reflected to incident, remained smaller than 0.1 for the present wave absorber when encountering long waves with 7.04 m in experiments with a typical water depth h = 0.4 m. The working principle of resonant wave absorber is further clarified by revealing the wave components outside the wave absorber.