| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 99 === In this paper, numerical simulation was presented to investigate the characteristics of waves on a seawall. The numerical method is based on three dimensional RANS equation and RNG turbulence model, then finite difference method, FAVOR grid obstacle processing technique and volume of fluid method are used for finding the solution. In this paper, the wave flow field chart experimented by Tsai et al. (1998) was used for numerical simulation verification, and the results showed that the simulation result and the experimental result had good match. In this article, different slope angle of dike, three types of dike toe water depths d (0.4m, 1.2m, 2.0m) of slope sea dike and stepwise sea dike, different dike toe speed, different run-up height, different turbulence energy and different turbulent dissipation characteristics will be investigated.
From the simulation results, it can be seen that under the slow-down of the slope of the dike surface, the down-rush water flow will tend to have weaker action on the dike toe. When the slope is slowed down and when the wave acts on the dike surface, the broken wave form will be plunging type broken wave. In the run-up process of stepwise sea dike, it will generate clockwise vortex, and during the down-flow process of the water, it will generate counter clockwise vortex. The run-up height and down-rush speed will be affected by non-continuous effect of the stair, hence, the run-up height will be reduced, and the down-rush water flow speed will be slowed down too. Therefore, it can be seen that the stepwise dike can produce good effect. For slope dike, larger turbulent dissipation will be generated only when the wave collide with the dike surface, but for stepwise sea dike, when the wave acts on the dike surface, during the process when water runs up or brushes down along the dike surface, vortex will be formed in the triangular area within the stair, in the mean time, when the water flows down, pretty good energy dissipation effect can be generated due to the vortex.
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