WAVES ON PERMEABLE LAYERS

Toru Sawaragi, Ichiro Deguchi

Abstract


To analyze a wave attenuation on a permeable layer, we first examined the applicability of Forchheimer type equation to the fluid motion in the permeable layer through permeability tests in steady and unsteady flows. Then, we investigated the effects of a boundary shear on the surface of the permeable layer on the wave attenuation by solving boundary layer equations around the surface of the layer. It is found that the permeability and the turbulent drag coefficient in the Forchheimer type equation in the unsteady flow are different from those in the steady flow. We showed that the Forchheimer type equation could linearlize by using an equivalent linear drag coefficient formulated empirically through the permeability test. The effect of the boundary shear on the wave attenuation on the permeable layer was small compared with the effect of energy loss in the permeable layer if the thickness of the layer was relatively large. It is also found that we can predict the wave attenuation on the permeable layer exactly when the incident wave has a strong linearity.

Keywords


permeable layer; rubble mound

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