波浪在珊瑚岸礁礁坪上传播变形的数值研究

Numerical study of wave transformation over fringing reef flat

波浪的传播变形对珊瑚岛礁附近的营养物质输送以及近岸珊瑚沙运动都起着关键的作用,同时也是礁盘顶部建筑物在设计和施工过程中需要重点考虑的因素,因此,对波浪在礁坪上的传播变形进行研究具有重要意义。利用FUNWAVE 2.0数值模型模拟了不规则波浪在不同形状岸礁上的传播变形过程,讨论了礁前斜坡坡度以及珊瑚底面粗糙程度对波浪在礁坪上传播变形的影响。结果显示,随着礁坡斜率增大,不对称度参数绝对值的增长趋势逐渐变缓,波浪在光滑礁坪上的不对称度绝对值要略大于粗糙底面上的值,而不同地形下计算得到的波浪偏度参数则基本相同。说明礁坡坡度对波浪的不对称度特征具有显著影响,礁坪粗糙度的影响则相对较小,而上述因素对波浪偏度的影响则完全可以忽略。给出了考虑这两个影响因素的礁坪区域内波浪偏度和不对称度经验公式。

The evolution of wave shapes on fringing reefs is closely related to nearshore nutrient delivery and sediment transport of coral sand. It also plays a crucial role in determining the design and construction of the structure on the reef flat. Therefore,investigating the evolutions of wave shapes on the reef flat is necessary. In this paper,the FUNWAVE 2. 0 numerical model was employed to simulate irregular waves,which propagate over different types of fringing reefs,and the influence of forereef bottom slope and reef roughness on the evolution of wave shapes was discussed. Results showed that an increase in the absolute value of wave asymmetry is moderated by the slope of the forereef bottom becoming steeper. Moreover,the absolute value of asymmetry for the smooth bed condition is slightly larger than that for the rough bed condition. However,the wave skewness on different fringing reefs is almost the same. This indicates that the forereef bottom slope significantly influences wave asymmetry variation and the effect of reef roughness is relatively small. However,the abovementioned factors have a negligible effect on the wave skewness. In conclusion,the empirical formulae for wave skewness and wave asymmetry on the reef flat by combining the influence of forereef bottom slope and reef roughness are recommended.