人工采掘坑影响下珊瑚礁海岸波浪传播变形试验

Laboratory study on the effect of artificial excavation pit on wave transformation of coral reef coast

基于礁坪上高分辨率的波浪测量,通过波浪水槽试验分析了短波、低频长波、平均水位、波形参数和非线性参数的沿礁变化规律,重点探讨礁坪中部存在人工采掘坑对上述波浪传播变形特征的影响,并与无坑的情况进行对比。研究表明:当人工采掘坑存在时,短波波高在坑前和坑内分别增大和减小,在礁后岸滩附近却无显著变化;低频长波波高在坑附近变化不大,在岸滩附近却略微减小;波浪增水在坑和岸滩附近均无显著变化。采掘坑存在的情况下,波浪的偏度和不对称度在坑附近分别减小和增大,而厄塞尔数在坑附近却几乎不变。相关性分析发现低频长波的产生机理几乎不受采掘坑的影响,采掘坑的存在增加了低频长波的反射,破坏了礁坪的共振模式,从而使低频长波在岸滩附近有所削弱。

Based on the high-resolution wave measurements on the reef flat,wave-flume experiments were conducted to analyze the variations of sea and swell waves,infragravity waves,mean water level,wave shape parameters and nonlinearity parameter along the reef profile.The emphasis is given to the effects of an artificial excavation pit locating in the middle of the reef flat on the wave transformation characteristics mentioned above.Compared to the case in the absence of excavation pit,the results show that the sea and swell wave height increases and decreases in front of and inside the pit,respectively,but there is no notable change of the wave height near the back-reef beach.The infragravity wave height does not vary significantly near the pit,but it decreases slightly near the beach.There is almost no variation of wave setup around both the pit and the beach.The wave skewness and asymmetry decreases and increases,respectively,near the pit,while the Ursell number is almost unvaried.A cross-correlation analysis indicates that the mechanism of infragravity wave generation is unaffected by the excavation pit,whereas the presenceof pit both increases the wave reflection and disrupts the resonant modes on the reef flat,leading to a decline of the infragravity wave height near the beach.