Two-dimensional laboratory experiments and numerical simulations were performed to clarify changes that occur in a breaking wave as it passes over a submerged breakwater. Spatial distributions of the flow pattern, velocity, and vorticity were measured using video images and a Particle Tracking Velocimetry (PTV) flow visualization system In the numerical analysis, we used an improved Simplified Maker and Cell (SMAC) method to calculate changes in the breaker as it passed over the submerged breakwater. A comparison of the numerical and experimental results confirmed the validity of the numerical method.
Wave motion, especially wave breaking plays an important role in sediment transport and beach profile change. Impact breaking wave pressures can transform coastal structures. As a result, an important consideration in coastal engineering is understanding the internal characteristics of breaking waves. To date, many theoretical and experimental studies have been carried out to learn more about breaker transformation. In recent years, due to advances in measuring techniques such as Laser-Doppler Velocimetry (LDV) and Video Tape Recording (VTR), new information about the turbulence structure and velocity fields in surf zones has been available (Stive, 1980; Nadaoka and Kondo,1982; Sakai et al.1982,1984; Hattori and Aono, 1985; Okayasu et al., 1986). However, because wave breaking is a violent phenomenon with many entrained air bubbles, the extent to which the breaker transformation can be clarified through experimentation is limited. Therefore, in this paper we attempt to clarify the internal characteristics of the breaking wave over a submerged breakwater through both experimentation and numerical simulation. It is possible to perform flow analysis using the velocity potential theory prior to the impingement of the water mass by the breaker. Possible methods include the Boundary Element Method (BEM, Longuet-Higgins and Cokelet, 1976) and the Finite Element Method (FEM, Takikawa et al., 1983).
