Water-level controls on macro-tidal rip currents
Water-level controls on macro-tidal rip currents
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DOI：
10.1016/j.csr.2013.12.004
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发表时间：
2014-03-01
影响因子：
2.3
通讯作者：
Russell, Paul E.
中科院分区：
文献类型：
--
作者：
Austin, Martin J.;Masselink, Gerd;Russell, Paul E.
本文采用现场观测和数值模拟的方法，研究了大潮海滩上裂流动力学对水位的控制作用。现场收集的数据超过32个完整的潮汐周期，跨越一系列的波浪和潮汐条件，表明，裂流强度和行为调制在半日频率的潮汐引起的变化，在酒吧/RIP形态的水位。裂颈中的峰值流速（< uv >）对应于低潮前后1.5 h的最大波浪破碎时间。沿补给水道和潮间拦门沙末端周围沿着测量了沿岸水面梯度偏导数eta/偏导数y，水头差为O（0.1 m）。数值模型以良好的技术水平再现偏导数eta/偏导数y，并显示偏导数eta/偏导数y和< uv >随着潮间沙洲上破碎波的比例Q（B）而增加;但< uv >在峰值Q（B）期间最大，当波浪破碎移动到潮下沙洲时，最大偏导数eta/偏导数y出现，Q（B）减小。在低水位附近，沿岸压力驱动的馈线电流对裂流的强迫通过在酒吧和馈线区域Q（B）的减少而减少，但是通过裂水道的离岸流通过在潮间酒吧两端附近局部强化偏导数eta/偏导数y而得以维持。(C)2014作者由爱思唯尔有限公司出版。保留所有权利。
Field measurements and numerical modelling have been used to investigate the water-level control of rip current dynamics on a macro-tidal beach. Field data collected over 32 complete tidal cycles, spanning a range of wave and tide conditions, demonstrate that rip current strength and behaviour is modulated at the semi-diurnal frequency by tide-induced changes in the water-level over bar/rip morphology. Peak flow speeds in the rip neck (< uv >) correspond to the time of maximum wave breaking 1.5 h before and after low water.Alongshore-directed water surface gradients partial derivative eta/partial derivative y were measured along the feeder channel and around the ends of the inter-tidal bar, with head differences O(0.1 m). The numerical model reproduced partial derivative eta/partial derivative y with a good level of skill and showed that partial derivative eta/partial derivative y and < uv > increase with the proportion of breaking waves Q(b) over the inter-tidal bar; but < uv > was maximised during peak Q(b), maximum partial derivative eta/partial derivative y occurred when wave breaking moved offshore to the sub-tidal bar and Q(b) was reduced. Around low water, the forcing of the rip current by the alongshore pressure-driven feeder current was reduced by the decrease in Q(b) over the bar and feeder regions, but an offshore flow through the rip channel was maintained by a localised intensification of partial derivative eta/partial derivative y around the ends of the inter-tidal bar. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.