The Study On Wave Motion In Rubble Mound Breakwater

This paper studies the wave motion in rubble mound breakwater by discarding the homogeneous assumption. The blocks in the section of breakwater are generated randomly, and the region outside the breakwater is meshed into grids. By taking the blocks as wall boundaries, the fluid field is calculated using finite element method.The seepage field in the breakwater is calculated with Fluent software. The whole field is air-water two-phase flow, and the free-surface is dealt with Volume Of Fluid method. To verify the validity of Fluent software, corresponding tests are performed. By comparing the results of calculation and tests, we can safely say that Fluent software is accurate enough to solve the wave motion in rubble mound breakwater.A large number of numerical tests are performed on the breakwaters with different porosities and different block radius. The results show that the force on blocks is affected by many factors, such as the porosity of the breakwater, the shape of the breakwater section, the average radius of the blocks, the arrange of blocks, and the wave conditions including wave period, wave height, and wave length etc. The transmission of waves relates to the porosity and the wave length, the larger the porosity and the longer the wave length the larger the transmission. Commonly the transmission is small. The pressure varies greatly in different places. The dynamic pressure is largest in front of the breakwater around the free-surface, and it is also very large in the front foot of the breakwater and in the rear of the breakwater around free-surface. Seeing from the force of single block, it varies greatly in different places at different time. At a fixed time, the forces are very small on most blocks but for the ones being in front of the breakwater around the free-surface. The largest force on the blocks also varies greatly at different time, but the location of blocks are fairly fixed. From the results of numerous models it can be concluded that the largest force on blocks decreases with the increasing of porosity of breakwater and the average radius of blocks.