不规则波在孔隙介质礁坪上传播过程的波高和增水变化数值研究

采用$sigma $坐标系统下以体积平均的雷诺时间平均方程作为控制方程的三维非静压模型，对随机波浪在带有孔隙介质的岛礁地形上的传播过程进行了模拟，重点分析了礁坪上方波高和增水的变化。通过与多个组次工况的物理模型实验数据进行对比，结果显示，本文模型能很好地模拟波浪在孔隙介质上传播演化的过程，与实验结果吻合程度很高。分析结果表明，相比于光滑底床，孔隙介质的存在造成破碎点附近波高平均下降12%，礁坪上方波高平均下降28%。对于平均水位，孔隙底床条件下的最大减水幅值减小了43%，同时礁坪上方增水幅值上升6%。另外，孔隙率在0.47～0.87范围内变化时，对礁坪上方平均水位的变化基本无影响。

A numerical investigation on wave height and wave setup of irregular wave propagation at the reef flat with porous media

A three-dimensional non-hydrostatic model based on volumed-averaged, Reynolds-averaged Navier-Stokes (VARANS) equations in sigma coordinate, is applied to simulate the propagation process of irregular wave over a typical fringing coral reef profile, with emphasis on the changes of wave height and wave setup on the reef flat. Compared with the laboratory measured data of several groups of wave and water level parameters, the model is shown to be capable of simulating well the wave transformation over the reef profile with and without porous media. Across all cases, the porous cases decrease the wave height by 12% around the breaking point, and by 28% on the reef flat than the smooth cases. As for the mean water level, the results show that the maximum setdown decreases by 43% on average for the porous cases than the smooth cases, while the wave setup on the reef flat for corresponding porous and smooth simulations is found to agree with an average difference of only 6%. In addition, the variation of porosity in the range 0.47−0.87 auses little effect on the wave setup.