Wave-driven currents and vortex dynamics on barred beaches
Wave-driven currents and vortex dynamics on barred beaches
复制标题
禁止海滩上的波浪驱动的水流和涡流动力学
DOI：
10.1017/s0022112001006322
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发表时间：
2001
影响因子：
3.7
通讯作者：
T. Jacobson
中科院分区：
文献类型：
--
作者：
O. Bühler;T. Jacobson
我们提出了一个理论和数值研究沿岸流破碎波驱动的海滩，特别是禁止海滩。这里考虑的新功能是，波的包络线被允许在沿岸方向上变化，这导致产生强偶极涡结构的波浪破碎。这些涡结构的非线性演化进行了详细研究，使用一个简单的分析理论模型的倾斜海滩的影响。我们的研究结果之一是，涡的演变提供了一个强大的机制，通过该机制，沿岸流的首选位置可以从波浪破碎的位置向岸边移动。在真实的拦岸滩上，这种水流错位是一种经常观察到的（但难以理解的）现象。为了支持我们的研究结果，我们提出了一个全面的理论描述相关的波平均相互作用理论的背景下，浅水模型的海滩。在这里，我们联系的辐射应力理论的Longuet-Higgins和斯图尔特最近建立的结果有关的平均涡产生由于破碎波。这导致详细的结果，平均流涡演变的整个生命周期，从它的初始生成波破碎，直到其最终耗散衰减由于底部摩擦。为了检验和说明我们的理论，我们还提出了理想化的非线性数值模拟的波浪和涡使用全浅水方程与底部地形。在这些模拟中，波浪破碎通过浅水波的冲击形成而发生。我们注意到，因为浅水方程也描述了二维流动的同熵理想气体，我们的理论和数值结果也可以应用到非线性声学和声涡相互作用。
We present a theoretical and numerical investigation of longshore currents driven by breaking waves on beaches, especially barred beaches. The novel feature considered here is that the wave envelope is allowed to vary in the alongshore direction, which leads to the generation of strong dipolar vortex structures where the waves are breaking. The nonlinear evolution of these vortex structures is studied in detail using a simple analytical theory to model the effect of a sloping beach. One of our findings is that the vortex evolution provides a robust mechanism through which the preferred location of the longshore current can move shorewards from the location of wave breaking. Such current dislocation is an often-observed (but ill-understood) phenomenon on real barred beaches. To underpin our results, we present a comprehensive theoretical description of the relevant wave–mean interaction theory in the context of a shallow-water model for the beach. Therein we link the radiation-stress theory of Longuet-Higgins & Stewart to recently established results concerning the mean vorticity generation due to breaking waves. This leads to detailed results for the entire life-cycle of the mean-flow vortex evolution, from its initial generation by wave breaking until its eventual dissipative decay due to bottom friction. In order to test and illustrate our theory we also present idealized nonlinear numerical simulations of both waves and vortices using the full shallow-water equations with bottom topography. In these simulations wave breaking occurs through shock formation of the shallow-water waves. We note that because the shallow-water equations also describe the two-dimensional flow of a homentropic perfect gas, our theoretical and numerical results can also be applied to nonlinear acoustics and sound–vortex interactions.