Broadband omnidirectional absorption for linear liquid surface wave

•Design of a broadband omnidirectional absorber for linear liquid surface wave.•Study of absorption for non-dispersive linear liquid surface wave.•Study of absorption for dispersive linear liquid surface wave.

We investigate the propagation of linear liquid surface wave (LLSW) over an omnidirectional absorber (OA), which has uneven bottom with appropriate gradient depth distribution. The OA consists of a guiding shell with gradient bottom topography and a central absorptive cavity. The non-dispersive shallow-water wave equation model and the dispersive mild-slope equation model are employed to investigate the absorption properties of the OA. The results show that almost omnidirectional incident LLSW can be spirally deflected from the interface to the center in the guiding shell and finally absorbed by the central cavity. The introducing of guiding shell enlarges the absorption cross section of the bare absorptive cavity from the inner diameter to the outer diameter of the OA, resulting in high absorption efficiency. Furthermore, the proposal can be constructed by simple modulation of the liquid bottom, which may significantly facilitate the engineering applications.