Modeling on Transformation Process of Beach Profiles

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This project has been carried out to obtain fundamental knowledge which describes the mechanism of beach transformation under wave action. Large scale vortices generated by wave breaking play an important role for the sediment movement in the surf zone. To clarify the mechanism, Sakai has performed a numerical analysis with a marker and cell method to simulate a violent motion after an impinging of a jet from a crest of a plunging breaker. Asano has calculated the turbulent energy close to a bottom under wave motion with a k-e model, and investigated the sediment concentration under the calculated turbulent energy by using a stochastic method. Mase has proposed a calculation model of random wave transformation including wave breaking on a uniform slope. The model gives useful information for the sediment movement under random waves. Hirayama has developed a new theory concerning the mass transport velocity due to waves on a uniform slope. The result is important because the mass transport velocity is closely related to the sediment movement. Iwagaki has summarized the above fundamental results and clarified that the transformation of a beach profile can be explained by the spatial variation of the net velocity of a sediment.