Flow Characteristics in run-up of periodic waves on nonuni form slope

点击翻译按钮获取中文摘要

Swash zone is a portion of the nearshore region in which the beach face is alternately covered by the uprush of the wave swash and exposed by the backwash. Violent fluid motion under the swash flow creates high turbulence and gives rise to a strong sediment movement, which causes constantly beach profile changes in swash zone.Because of the very complex flow, there is fair less information about the mechanical behaviors of wave swash. Many studies of the physical processes occurred under swash have been required if we are better understand beach processes in the swash zone. This is the main purpose of the present study.Comprehensive experiments were made in a wave tank in which model beaches of fixed and movable beds with various slopes were installed. The flow field under swash waves is of high nonlinear and unsteady. In addition, the water depth is extremely shallow. It is, therefore, impossible to measure the flow velocity on a slope. We developed a practical and reasonable procedure for evaluating the flow velocity with the aid of nonlinear long wave theory based on video pictures of the free surface profile.Experiments reveal that mode of incident waves changes from undular bore to swash through the bore collapse process. The bore collapse plays an important role in wave run-up processes. Bottom shear stress contributed to sediment transport is varied temporally and spatially with a time lag between the local fluid velocity.The findings of this research should be taken account of in modeling the swash zone processes.