Investigation Of Interaction Between Breaking Wave And Vertical Breakwater

Vertical breakwater is commonly used in port and coastal engineering. Wave force is one of the major forces the vertical breakwater endures. Breaking wave may cause great damage to the vertical breakwater. Since the mechanism of wave breaking is so complex with aeration and intense turbulent motion, the mechanism of breaking wave acting on the vertical breakwater haven't been fully understand so far.The work of this paper is supported by the National Natural Science Foundation of China titled: "Investigation of Wave Breaking Mechanism and Its Action on a Vertical-wall Architecture" (No.50679008). Physical model test and numerical simulation are both adopted to study the characteristics of wave pressure and the relation between the pressure and flow field in regular waves. The major work of the paper are about breaking standing wave and breaking wave. The particle image velocimetry (PIV) technique is adopted to work synchronously with pressure measurement sensor in physical model test. The flow vectors and pressures are obtained synchronously. A two-dimensional numerical wave flume is established based on finite element method (FEM) and volume of fluid (VOF) technique in numerical simulation.The pressure distributions, wave forces, pressure time series, and flow fields computed by numerical simulation are compared with that obtained by physical model test. It indicates that using this numerical model can calculate the pressure of breaking wave well and simulate the process of wave propagating, deformation, and breaking before the vertical breakwater.The breaking standing wave's flow field is similar to that of standing wave. According to standing wave theory, the saddle-like pressure time series are caused by nonlinearity, the wave breaking makes the saddle shape more apparent. The wave forces of breaking standing wave calculated by method proposed by Design Code are much larger, which indicates adopting the code method to calculate wave force of breaking standing wave may be too conservative.When the breaking wave impacts the vertical breakwater, the pressure induced by wave impacting plays an important role, which leads to the first pressure crest. When the wave surface climbs along the breakwater, the pressure begins to decrease as the impacting disappears and the wave breaking. When the wave surface begins to come down, the upper water impacts the lower water, which induces the second pressure crest. The wave breaking type differs as the elevation of the breakwater foundation crest goes up. Under moderate-crest foundation condition, the wave crest is collapsing; under high-crest foundation condition, the wave crest is wrapping. The different breaking types result in different types of pressure time series. In the case of moderate-crest foundation, the pressure time series is saddle-like, which means there are two pressure crests and the height of them are close to each other. In the case of high-crest foundation, there are still two crests, and the first one is much larger then the second one, as the first one is induced by wave impacting.