Cross-shore distribution feature of longshore currents over barred beaches
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摘要: 通过对两个坡度沙坝地形沿岸流实验测量和基于能量方程的沿岸流数值模拟,研究了沙坝海岸平均沿岸流速度剖面的双峰剖面特征,重点分析了第二个峰值的特征和两峰值的比值。综合考虑入射波高、入射波类型和坡度对波生沿岸流垂直岸线速度剖面的影响。结果表明,平均沿岸流速度剖面出现双峰剖面特征:第一峰值发生在沙坝向岸侧面的中部,第二个峰值发生在靠近岸线处;同一坡度情况两个峰值的位置和比值,不受入射波类型、入射波高的影响。数值模型中包括了侧混、底摩擦和水滚等因素,其数值模拟结果和实验值拟合较好,并讨论了有无侧混和水滚对速度剖面的影响。Abstract: The experimental study on wave-driven longshore currents on barred beaches and numerical simulations which were based on wave energy conservation equation, were conducted to investigate the cross-shore distribution feature of velocity profiles of mean longshore currents, with emphasis on the second peak of longshore currents. The distribution feature of longshore currents has the velocity profile with bimodal characteristics. The larger one occurs on the middle part of lateral side of barred beaches and the smaller one is close to the shoreline, which corresponds to the first and second wave breaking respectively. The above features have been discussed by considering the effects of wave height, wave type and beach slope. The locations of two peaks and their ratio (i.e., higher one/smaller one) do not depend on wave type and wave height, but the location of barred beaches. Numerical simulations were also performed to compute the measured velocity profile with the emphasis on the effect of several factors such as lateral mixing, bottom friction and surface rollers on numerical results.
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Key words:
- bimodal profiles /
- two peak values /
- wave breaking /
- barred beaches
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