叠加波浪场作用下裂流三维分布特征研究

Three⁃dimensional Distribution Characteristics of Rip Currents Generated by Intersecting Waves

明晰叠加波浪场作用下裂流三维分布特征,有助于全面深入开展海岸裂流的演化规律和致灾机理研究.为分析丁坝、沙坝和沟槽对裂流三维特征的影响,通过对沟槽内和槽外沙坝上两个不同节点位置ADV流速测量,实验研究了有槽沙坝海岸交叉叠加波浪的裂流垂向分布.结果表明:对沟槽内和沙坝上节点断面,裂流头区域表现为靠近水表面具有较大速度的表面流特征.而对于裂流颈位置则有不同,沙坝上的裂流垂向结构变化较大,沟槽内的裂流垂向数值较为均匀.沟槽内断面的裂流垂向分布符合对数分布规律.裂流沿岸速度分量表现为上大下小的规律,但对于不同周期略有不同.丁坝通过控制近岸环流系统而影响裂流沿岸速度分量的波动特征,导致沟槽内裂流的沿岸速度分量指向丁坝方向,对距离丁坝较远的沙坝上裂流的沿岸速度分量影响减弱.

The study of three⁃dimensional distribution of rip currents by intersecting waves is helpful to the comprehensive study of evolution laws and disaster mechanisms.To better analyze the influence of groin,sandbar and rip channel on the three⁃dimensional distribution of rip currents,an experimental study on vertical structure of rip currents generated by intersecting waves over barred beaches with rip channels was conducted at two different nodes in rip channel and on the sandbar.The results show that offshore from the sandbar the rip current velocities were much stronger at the surface than near the bottom.The vertical structure of rip currents was found to vary from depth⁃uniform in rip channel and strongly depth⁃varying on the sandbar.The results show that the vertical structure of rip currents is in accordance with the logarithmic distribution law.The nearshore circulation system and the fluctuation characteristics of the longshore velocity component of the rip currents by the groin,which results in that the longshore velocity component of rip currents in the rip channel points to the direction of the groin,and weakens the influence on longshore velocity component of rip currents on the sand bar far away from the groin.