Tidal Synchronization of Lee Vortices in Geophysical Wakes
Tidal Synchronization of Lee Vortices in Geophysical Wakes
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DOI：
10.1029/2020gl090905
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发表时间：
2021-01
影响因子：
5.2
通讯作者：
Pranav S. Puthan;S. Sarkar;G. Pawlak
中科院分区：
文献类型：
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作者：
Pranav S. Puthan;S. Sarkar;G. Pawlak
本文用大涡模拟方法研究了分层流体中经过锥形丘的潮汐调制流中的尾涡。涡流脱落频率从其自然稳流值发生变化，导致尾涡与潮汐同步。相对频率（f*），定义为自然脱落频率（fs，c）在当前没有潮汐的潮汐频率（ft）的比率，是不同的，以暴露不同的制度的潮汐同步。当f* 增大并接近0.25时，体部的旋涡脱落从经典的非对称卡门涡街改变。尾流向下游发展以恢复卡门涡街不对称性，但发现与尾流涡相关的离散谱峰与ft和fs，c不同，这是一个新的结果。当0.5 ≤ f* < 1时，谱峰出现在潮汐频率的第一次谐波处;当0.25 ≤ f* < 0.5时，谱峰出现在潮汐频率的第二次谐波处。
Wake vortices in tidally modulated currents past a conical hill in a stratified fluid are investigated using large‐eddy‐simulation. The vortex shedding frequency is altered from its natural steady‐current value leading to synchronization of wake vortices with the tide. The relative frequency (f*), defined as the ratio of natural shedding frequency (fs,c) in a current without tides to the tidal frequency (ft), is varied to expose different regimes of tidal synchronization. When f* increases and approaches 0.25, vortex shedding at the body changes from a classical asymmetric Kármán vortex street. The wake evolves downstream to restore the Kármán vortex‐street asymmetry but the discrete spectral peak, associated with wake vortices, is found to differ from both ft and fs,c, a novel result. The spectral peak occurs at the first subharmonic of the tidal frequency when 0.5 ≤ f* < 1 and at the second subharmonic when 0.25 ≤ f* < 0.5.