Wave Motion through Porous Structures

Abstract

Linear potential theory is applied to the analysis of wave motion through a two‐layer porous structure. For special cases, the characteristics of waves in nondissipative, weakly, as well as strongly, dissipative media and their relations with the inertial and resistive properties of the media are explored. It is noted that in a nondissipative medium, the wave components are either nonpropagative or nondecaying. In a dissipative medium, however, they are always propagative and decaying as well. The reflection, transmission, and dissipation of monochromatic incident waves by a rectangular block, with typical dissipative characteristics and various thickness as well as submergence of its crest, are studied by the method of matched velocity potentials. It is found that there is an optimum thickness for a porous structure beyond which any further increase of the thickness may not lead to an appreciable improvement of its functional performance in reducing the transmission and reflection. It is also discovered that a medium of moderate permeability may be favorable in the design of a wide‐crested breakwater if the wave heights on both front and lee sides of the structure are required to be controlled.