WAVE REFLECTION BY A NUMBER OF THIN POROUS PLATES FIXED IN A SEMI-INFINITELY LONG FLUME

S.W. Twu, D.T. Lin

Abstract


The reflection of small-amplitude surface waves by a number of vertical porous plates is investigated . The plates are fixed in a semi-infinitely long channel of constant depth.Analytic solutions in dimensionless closed from are presented for the surface wave profiles in the several regions separated by these plates . And from them the reflection coefficient is obtained . Three cases , one to three porous plates, are evaluated. The results show that for incident waves in the range of 1/20 < water depth/wave length < 1/2 , it is appropriate to maintain the spacing between every two adjoining plates,and between the end wall and its nearst plate at a value of 0.88 times the water depth. As two or three porous plates are used for damping wave , an arrangement would be more effective if the front porous plate has a larger porosity and the back one has a smaller porosity. Several experimental tests for these porous-plate wave absorbers are conducted and the reflection coefficients are measured by using Goda's method. It is found that the theoretical solutions agree fairly well with the experimental results.

Keywords


wave reflection; porous plate; flume; semi-infinite flume

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