Diffraction waves on large aspect ratio rectangular submerged breakwaters

Abstract

In this paper, hydrodynamic characteristics of two-dimensional submerged breakwaters in water of finite depth and infinite domain interacting with sinusoidal waves are studied from both analytical and numerical approaches. Added mass and damping coefficients are obtained following the determination of radiation potentials in three degrees of freedom (sway, heave and roll). Diffraction problem is then solved according to the linear wave theory and the resulting forces are derived. To verify the results, a comparison of the solution from the analytical method with those obtained by the boundary element method is made and a good agreement is observed. Additionally, high aspect ratio horizontal and vertical flat submerged breakwaters are proposed and their hydrodynamic characteristics are analysed using the numerical and analytical methods. Results show that the horizontal flat submerged breakwater generates low transmitted waves. However, the vertical flat submerged breakwater transmits almost the entire incident wave energy. A parametric study on the effect of submergence depth and the width of the structure on the maximum diffraction wave amplitude, which is responsible for the transmitted wave energy, is carried out and a better understanding of the variation of diffraction wave amplitudes with respect to dominant parameters and wave frequency is achieved.