Experimental demonstration of perfect water wave absorption

We report an experimental demonstration of perfect wave absorption applied, for the first time, in the case of surface water waves. We used a Helmholtz-type resonator coupled to a mono-mode waveguide, which generates radiation damping. By tuning the geometry of the resonator, we found the equilibrium between the radiation damping and the intrinsic (viscous) damping of the system, which yields perfect absorption. Additionally, by varying the incident wave amplitude, we tuned the nonlinear resistance and consequently the intrinsic damping. In this case, we also obtained a perfect absorption, now as a function of the nonlinearity. The accuracy of the experimental set-up allowed us to measure absorption around 99%.