珊瑚礁破碎带附近波浪演化和波生流实验研究

Experimental study of wave transformation and wave-driven current around the surf zone over coral reefs

为了研究珊瑚岸礁破碎带附近波浪演化和波生流特性,通过水槽实验对规则波浪作用下珊瑚岸礁上沿礁分布的水位和流速进行了详细的测量。在典型卷破波条件下,测试了礁冠存在与不存在的两种情况。实验结果表明,多重波浪反射作用引起岸礁上形成不完全驻波,而破碎带附近的浅化作用则产生高次谐波,波浪破碎所耗散的波能主要来源于主频波,礁坪上透射波成分中二次谐波与主频波的能量相当;礁冠的存在引起破碎带宽度减小、礁坪上增水变大以及礁坪上各次谐波变小;礁冠不存在时,岸礁上波生流的沿礁分布与平直海岸相似,而礁冠的存在一定程度上阻碍了礁坪上水体向外海的回流。研究成果将丰富和发展珊瑚礁水动力学理论,并为岛礁工程的建设和维护提供一定的理论参考。

To investigate the wave transformation and wave-driven current around the surf zone over fringing reefs,a series of laboratory experiments are performed in a wave flume to measure the cross-reef water lever and flow in details.Experimental results are reported for two reef profiles with and without the reef crest under a typical plunging breaker condition.Data analysis shows that partial standing waves across the reef are formed due to multiple wave reflection,and higher harmonics around the surf zone are generated through wave shoaling.The energy dissipation in the surf zone results primarily from the dissipation of fundamental harmonics,and the resultant second harmonic waves are comparable to the fundamental harmonics on the reef flat.The presence of the reef crest reduces the surf zone width,increases the wave-induced setup,and decreases the harmonic wave amplitudes on the reef flat.The variation of the wave-driven current across the fringing reef without the reef crest is similar to that for the plane beaches.The existence of the reef crest causes the retention of the mean-flow on the leeside of the crest to some extent.