有槽沙坝海岸交叉波浪作用下裂流特征

Rip currents by intersecting wave on barred beach with rip channel

研究叠加波浪场作用下的裂流特征,有助于全面深入开展海岸裂流的致灾机理及风险评估。为分析水动力和水底地形共同作用下形成的裂流特征,开展了交叉叠加波浪作用下有槽沙坝海岸的裂流流动特征试验,即同时考虑沿岸地形变化(存在沟槽)和交叉波浪共同作用所形成裂流。通过对裂流槽附近ADV(Acoustic Doppler Velocimetry)流速测量结果,分析叠加波浪场和裂流沟槽同时存在时所产生的裂流分布特征。裂流中心位置和宽度受裂流槽和波浪节点共同控制,裂流长度依赖于波高和海岸坡度。无槽情况裂流的驱动力主要是由波浪沿岸不均匀所产生的平均水面沿岸压力梯度,有槽情况裂流的驱动力由平均水面沿岸压力梯度和辐射应力沿岸梯度共同决定,二者量值相对大小依赖于波浪周期。

The study of rip currents by intersecting waves is helpful to the comprehensive study of disaster mechanisms and risk assessment.To better understand the characteristics of rip currents controlled by hydrodynamic forcing and longshore topographical variability,an experimental study on rip currents by intersecting waves over barred beaches with rip channels is conducted.The investigation focuses on the distribution characteristics of rip currents resulting from intersecting waves and longshore topographical variability.Analytical results of velocity distribution measurements by acoustic Doppler velocimeters are presented for the distribution characteristics of rip currents on barred beaches with rip channel.The location and width of rip currents are controlled by rip channel and wave nodes,and the length of the rip currents depends on the wave height and coastal slope.The driving force of rip currents without rip channel is primarily determined by the alongshore pressure gradient of the wave setup caused by intersecting waves.By contrast,the driving force of rip currents with rip channel is determined by both the alongshore pressure gradient of the wave set-up and the radial stress gradient,and the relative magnitude of the two values depends on the wave period.