Scattering of gravity waves by a pontoon type breakwater with a series of pervious and impervious skirt walls

Abstract

The scattering of surface gravity waves by a skirt wall breakwater is analysed in two dimensions under the assumption of small-amplitude wave theory. The oscillatory wave past the porous skirt walls is assumed to follow Darcy’s law. The boundary value problem is solved using multi-domain boundary element method to obtain the numerical results for the different number of porous skirt walls, relative pontoon width, relative submergence and different porosity of the skirt walls. The study reveals that an increase in the number of skirt walls from one to four can reduce the wave transmission by 61% but at the expense of an increase in horizontal wave force by 90% and decrease in the vertical force by 31%. A minimum of two-skirt walls is needed for reducing wave transmission. Skirt wall porosity of 0.40 is recommended for field applications considering the trade-off between the wave transmission and wave forces.