ABSTRACT:

The Bragg scattering of irregular waves propagating over rippled bed and rectified sinusoidal artificial bars is investigated in the present paper. Numerical simulation based on the EEMSE (Evolution Equation for Mild-Slope Equation) model including the wave-wave interaction and nonlinear shoaling effects is applied to describe the wave transformations on the undulated bottom. By using the numerical results of wave profile, Bragg reflection for irregular waves could be achieved. It is concluded that the distribution of reflection coefficients for irregular waves becomes more flat than that for regular waves. It is also noted that the resonant peak decreases and the bandwidth of resonance increases in the irregular wave cases.

INTRODUCTION

As waves propagate from deep sea to nearshore region, wave transformation takes place during the process owing to the bathymetry. In the surf zone wave energy dissipates and affects the nearshore hydrodynamics. In order to protect the beach, various kinds of coastal structures were established. In recent years hydrophilic structures, i.e. submerged breakwaters, have been introduced instead of traditional works to protect beach erosion when we consider the environmental impact. It reflects much of the incident waves and therefore reduces the energy of transmitted waves, the process thereby decreases the impact of the wave energy on the beach. Over the past decades, the surface waves scattered by the ripple seabed have been extensively studied, experimentally, theoretically, and numerically (e.g., Davies and Heathershaw, 1984; Mei, 1985; Hsu and Wen, 2001). As a practical application, the use of patches of sinusoidal bars often becomes unfeasible in coastal engineering technique due to many difficulties. For this reason, Kirby and Anton (1990) extended the previously existing theories concerning the Bragg reflection of surface waves by introducing artificial bars, which were placed discretely on the seabed.

This content is only available via PDF.
You can access this article if you purchase or spend a download.