Numerical Estimations of Wave Reflection Coefficient for Irregular Waves Over Submerged Obstacles

Abstract

Numerical simulations of irregular waves propagate over a set of submerged obstacles with various conditions are investigated in this study by means of boundary element method. The algorithm was based on the Lagrangian description with finite difference adopted for the approximation of time derivative. The accuracy of the model was first verified by studying the case of irregular waves propagating the water tank without any obstacle. Moreover, sets of submerged breakwaters are fixed under the water tank for investigation. An artificial absorbing beach represents here as sponge zone is employed at the other end of the flume to minimize the reflection effects. Power spectrum of Brestschneider-Mitsuyasu type defined by significant wave height, H1/3, and significant wave period, T1/3, employed for the condition of incident waves was chosen for the generation of irregular waves. Time histories of water elevations are measured with numerous pseudo wave gages on the free water surface, by comparing the spectra of these gages with the target, also refer to the methods for estimation of irregular incident and reflected waves in random sea presented by Goda & Suzuki, the dissipative efficiency of the breakwaters are therefore investigated. Gauges with different position are tested for their suitability of the estimations of reflection coefficients for irregular wave. In this paper, the results demonstrated the effectiveness of the estimation of reflection coefficient for random waves, which clarify the numerical model a feasible scheme.