An Experimental Investigation of Acceleration‐Skewed Oscillatory Flow Over Vortex Ripples
An Experimental Investigation of Acceleration‐Skewed Oscillatory Flow Over Vortex Ripples
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DOI：
10.1029/2019jc015487
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发表时间：
2019-12
影响因子：
--
通讯作者：
Jing Yuan;Dongxu Wang
中科院分区：
文献类型：
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作者：
Jing Yuan;Dongxu Wang
经源 1 、王东旭 1 通俗语言概要 在浅海沿岸地区，浅滩波浪产生振荡性底部流，在沙质海底产生沙 3 波纹。振荡流的加速度偏度是上覆水波的非线性特征 4 的结果，它可以区分振荡流的两个半周期 5 ，从而导致净（循环平均）沉积物输送。在这项研究中，我们使用振荡水洞和粒子图像测速技术来研究涡旋波纹上的振荡边界层流，重点关注加速度偏度的影响。 8 我们的测量结果详细描述了 9 个相干涡流的形成-喷射过程，该涡流是由波纹波峰后面的流动分离产生的。还提供了一些关于流动湍流的有用观察结果。结果表明，加速度偏度可以 11 显着地区分两个半周期内产生的两个相干涡旋。 12 离岸侧涡流可以比陆上涡流 13 在波纹波峰上携带更多的湍流，这可能会导致一些净陆上沉积物输送速率。我们还表明，14 波纹平均流量与平板上的流量相当接近，因此平板边界层模型 15 可以通过一些参数化用于波纹床。 16
Jing Yuan 1 , Dongxu Wang 1 Plain Language Summary In shallow coastal regions, shoaling waves produce oscillatory bottom flows, which create sand 3 ripples on a sandy seabed. The acceleration skewness of the oscillatory flow is a result of the 4 nonlinear feature of the overlying water waves, and it can differentiate the two half-cycles of 5 the oscillatory flow and therefore leading to a net (cycle-averaged) sediment transport. In this 6 study, we use an oscillatory water tunnel and particle image velocimetry to investigate the oscil7 latory boundary layer flow over vortex ripples with a focus on the effect of acceleration skewness. 8 Our measurements provide detailed descriptions of the formation-ejection process of coherent 9 vortices, which is produced by the flow separation behind the ripple crest. Some useful observa10 tions on flow turbulence are also provided. The results showed that acceleration skewness can 11 substantially differentiate the two coherent vortices developed within the two half cycles. The 12 offshore-side vortex can carry more turbulence over the ripple crest than the onshore-side vortex, 13 which possibly leads to some net onshore sediment transport rate. We also showed that the 14 ripple-averaged flow is fairly close to that over a flat bed, so flat-bed boundary layer model can 15 be possibly used for rippled bed with some parameterizations. 16