不规则波在筑堤珊瑚礁上传播的大水槽实验研究

Experimental study of irregular wave transformation on reefs with seawalls in large wave flume

基于大比尺波浪水槽模型实验,开展了不规则波在建有防浪堤的珊瑚礁陡变地形上传播变形规律的研究。采用弗劳德相似准则,通过1∶20的物理模型实验,模拟了不同水位和波高周期条件下,波浪从深水(d/L_0>1/2)到极浅水(d/L_0> 1/50)的传播-破碎-壅水过程。实验测得了陡坡19 m水深和7 m水深的浅水变形系数,结果表明波浪在陡变地形上的浅水变形系数与缓坡地形差别较大,且在一定范围内随相对水深的减小而减小;随着传播距离的增加,高频能量不断减小,能量会向低频转移,产生10倍以上入射波周期的低频波浪,且越靠近防浪墙,低频能量越大,水位壅高越大;利用低通滤波技术,测得了礁盘上壅水显著,结果表明防浪堤前的平均波浪增水与外海入射波高的平方成正比。

Irregular wave transformation and deformation on reefs with revetments was studied in large wave flume. The physical modeling was constructed with 1 ： 20 scaling by Froude law. The processes including wave transformation, breaking, and setup were reproduced from deep water （d/Lo〉 1/2） to shallow water （d/Lo〉 1/50）. Coefficient of shallow water deformation at 19 m and 7 m was obtained. In contrast to results at shallow slope, coefficient of shallow water deformation decreases as relative water depth decrease. When waves propagate over the reef plaffoml, the distribution of wave energy in the wave speetrum is changed with wave energy dominance shifting to lower frequency, and also waves with more than ten times longer period were observed. The closer it gets to revetments the speetrum peak will become higher. Wave setups over reefs are obtained according to low-pass filtering. The results show that wave setups in front of revetments are linear with square of wave height in deep water and are uneorrelated with wave period in deep water.