防浪建筑物影响下珊瑚礁海岸波浪传播变形试验

Laboratory study of wave transformation around reef coasts under effects of breakwaters

通过测试一系列不规则波工况研究了防浪建筑物存在下珊瑚礁海岸附近短波、低频长波和增水的变化规律,并对比了防浪建筑物的不同位置情况。分析结果表明:波浪在沿礁传播过程中,短波波高沿礁坪持续衰减,低频长波波高沿礁坪逐渐增大,波浪增水则沿礁坪基本保持不变;海岸附近短波随着防浪建筑物与礁缘距离的变大而减小,低频长波则在防浪建筑物处于礁坪后部时达到最大,防浪建筑物位置的变化对于礁坪波浪增水的影响可以忽略。通过理论分析证明了珊瑚礁地形上低频长波是由于群波破碎造成的破碎点移动而产生的;当特定波况作用于特定位置的防浪建筑物时,低频长波在礁坪上会发生一阶共振效应导致其能量在海岸附近达到最大值。

The swell waves,the infragravity waves and the wave setup around the reef coasts under the effect of breakwaters were investigated,and different positions of breakwaters were examined under a series of irregular wave conditions.The result analyses show that swell wave height continuously decays,infragravity wave height gradually increases,and wave setup keeps unaltered along the reef flat as waves propagate across the reef.Shoreline swell wave height decreases with the increasing distance between the breakwater and the reef edge,while shoreline infragravity wave height reaches its maximum when the breakwater is located at the rear part of the reef flat.The breakwater location seems to have insignificant effect on shoreline wave setup.Theoretic analyses show that the infragravity waves are generated by the breaking point shift during the group wave breaking.For the breakwater located at a specific position subjected to certain incident waves,the first-order resonance occurs on the reef flat associated with the infragravity waves,resulting in a peak energy level within the low-frequency band near the shoreline.