| With the construction and development of islands,and the increasing competition for marine resources,wave propagation and deformation near islands and reefs have become a hot issue that needs urgent solution.Coral reefs,characterized by extremely steep pre-reef slopes and a section of long reef flat,are widely distributed in the South China Sea,and are different from those of the ordinary inshore topography.The previous study on island and reef topography mainly focused on linear waves and the wave deformation and breaking of irregular waves at the reef margin and flat,but less was studied on nonlinear waves and wave deformation after climbing on islands and reefs.It was reported that in the construction of Nansha artificial islands,the design water level and wave height of the breakwater were obviously low,causing serious problems.Therefore,it is of great practical significance to study the waves climbing on the breakwater of coral reef topography.Based on FLOW-3D software,using boundary condition method to make waves and sponge layer damping method to eliminate waves,a two-dimensional numerical wave flume and coral reef topography wave climbing model is established to simulate the wave propagation of regular and irregular waves and the climbing process of breakwaters on different coral reef topography.In this thesis,the wave climbing differences between the coral reef breakwater and the flat breakwater,the law of wave climbing on the breakwater at different positions on the coral reef topography,and the relationship between regular wave and irregular wave climbing,are analyzed.The main work and conclusions of this thesis are as follows:1.Based on the established numerical flume,the breaking of nonlinear waves on the coral reef topography is numerically simulated.The comparison with the physical experiments shows that the experimental results are in good agreement with the physical experimental results.The reflected waves and wave heights of the simulated slope in front of the reef are basically consistent with the physical experimental results.2.Through numerical simulation,the wave climbing on the coral reef breakwater is compared with that the flat breakwater.The results show that due to the particularity of coral reef topography,the particle velocity,wave height and breakwater climbing are quite different from those of flat topography,and the wave climbing on coral reef topography cannot be calculated according to the wave climbing method of conventional topographic breakwater.3.Through numerical test of wave climbing on breakwaters of different topography,wave conditions and positions,the wave climbing is evaluated and analyzed.The results show that when the wave height is small,the position of the breakwater does not affect the waveclimbing on the breakwater;when the wave height is large,the wave climbing is very large in the breakwater close to the leading edge of the reef.With the increase of the distance between the breakwater on the reef flat and the leading edge of the reef,the wave height decreases obviously at first,and then tends to be stable.The climbing height of the breakwater at about one deep water wave length from the leading edge of the reef has significantly decreased,and the larger the wave height is,the more obvious the trend is.4.The relationship between regular wave and irregular wave climbing is obtained.In the case of large wave height,the 13% cumulative climbing of irregular wave is obviously smaller than that of regular wave;and the cumulative climbing of 4% of irregular wave is close to that of regular wave,only slightly smaller.The 1% cumulative rate is about 1.1 times higher than the 4% cumulative rate.In summary,a numerical model of wave propagation and breakwater climbing on coral reef topography is established based on FLOW-3D software,and the law of wave climbing on breakwater of coral reef topography is obtained.The results can provide scientific basis for the construction of breakwater on coral reef topography. |
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