A Locally Disordered Metamaterial for Directing and Trapping Water Waves

Manipulating the flow of water wave energy is crucial for ocean wave energy extraction or coastal protection, and the emergence of metamaterials paves a potential way for controlling water waves. In this work, by introducing a local disorder in a cavity-type metamaterial constructed by split-tube resonators, we show that water waves can be guided in an open channel with multiple energy flow paths formed merely by surrounded disconnected concurrent resonators that can serve as invisible walls without the requirement of a whole array system such as general periodic structures or waveguides. Specifically, we numerically and experimentally validate that a T-shaped metamaterial can achieve free guiding of water waves in a narrow band and a band-edge state along a distinct path. This open-space water waveguiding is found to be dominated by Fano-type interference and Fabry–Pérot resonance. Two distinct propagating modes, a low-frequency “trapping mode” and a high-frequency “following mode”, are identified. By simply rotating two configuration-dependent unit cells at the intersection of the metamaterial, we achieve a variety of water waveguiding paths tuning along rectilinear or bending (splitting or turning) directions, which rely on the two different propagating modes.