砕波帯内における水面渦度の推定法に関する一考察

抄録

The undertow is one of important factors which causes the disastrous erosion of beach. So far, the problems of this phenomenon have been treated both theoretically and experimentally by many investigators especially for elucidating the mechanics of transport of sediment. In order to establish the theory of undertow, it is essential to estimate quantitatively the vorticity of large-scale vortices induced on the water surface by breaking waves, because it is also one of main boundary conditions for solving the basic equation of undertow. Many theoretical estimation methods of the surface vorticity have been presented. Several ones are chosen for discussions and compared with each other in this paper. As a result, the calculation results of the surface vorticity by Nadaoka et al.'s method and Hirayama et al.'s one have a resemblance, and in comparison of the vertical distribution of undertow calculated by these methods with the experimental ones by Okayasu et al., it is shown that the surface vorticity has great effects on the vertical distribution characteristics of undertow.