Gravity Wave Interaction With a Composite Pile–Rock Breakwater

Abstract

Surface gravity wave interaction with a novel composite pile–rock breakwater having a stack of porous plates fixed on its top is investigated in the present study. A numerical code based on the dual boundary element method (DBEM) is developed to understand the wave scattering and force coefficients within the framework of linearized potential flow theory. Out of the four different proposed configurations (pile–rock alone, vertical, horizontal, and H-shaped porous plate assembly with pile–rock), it is found that novel H-shaped porous plates with submerged pile–rock are effective in attenuating the wave energy. The parametric study for the H-shaped configuration with several key aspects like permeable plate porosity, horizontal plate's submergence depth, pile–rock relative height, and width of the pile–rock barriers are investigated. It is appropriate to use plate porosity in the range of 10–20% to secure wave transmission of less than 0.5 for a wide range of incident wave periods. By changing the relative submergence of the horizontal porous plate from (h2/h = 0.375–0.125), it is possible to reduce the wave transmission by about 10% but at the expense of increasing the vertical wave force by almost 50–75%. Increasing the pile–rock height (h1/h from 0.75 to 0.25) helps to reduce the wave transmission but significantly increases the horizontal wave force and moment on the perforated H-shaped barrier. The results of the parametric study can be used for optimizing the dimensions of the pile–rock cum porous plate wave barrier for a wide range of field conditions.