Near-inertial-wave scattering by random flows
Near-inertial-wave scattering by random flows
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DOI：
10.1103/physrevfluids.1.033701
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发表时间：
2016-01
期刊：
影响因子：
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通讯作者：
Eric Danioux;J. Vanneste
中科院分区：
文献类型：
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作者：
Eric Danioux;J. Vanneste
利用线性浅水混合层模型研究了湍流对风驱动海洋近惯性波的影响。将流动建模为空间尺度与波长相当的均匀和平稳随机过程，我们推导出物理和光谱空间中的波能传输方程。该方程描述了流体对波的散射，其导致具有相同频率（或等效地，具有相同波数）的波之间的能量重新分布，并且对于各向同性流体，导致波场的各向同性。明确获得的散射和各向同性的时间尺度，并发现是典型的海洋参数的顺序为几十天。从输运方程推断的预测证实了一系列的数值模拟。通过专门的非线性浅水模拟，近惯性波的强烈影响，流散射的两种情况进行了研究。在第一，波包传播赤道作为结果从$\beta$-效应被证明是减慢和分散的纬向和纬向散射。在第二，移动的旋风所产生的波被证明是强烈的散射干扰，导致再次增加分散。
The impact of a turbulent flow on wind-driven oceanic near-inertial waves is examined using a linearised shallow-water model of the mixed layer. Modelling the flow as a homogeneous and stationary random process with spatial scales comparable to the wavelengths, we derive a transport (or kinetic) equation governing wave-energy transfers in both physical and spectral spaces. This equation describes the scattering of the waves by the flow which results in a redistribution of energy between waves with the same frequency (or, equivalently, with the same wavenumber) and, for isotropic flows, in the isotropisation of the wave field. The time scales for the scattering and isotropisation are obtained explicitly and found to be of the order of tens of days for typical oceanic parameters. The predictions inferred from the transport equation are confirmed by a series of numerical simulations. Two situations in which near-inertial waves are strongly influenced by flow scattering are investigated through dedicated nonlinear shallow-water simulations. In the first, a wavepacket propagating equatorwards as a result from the $\beta$-effect is shown to be slowed down and dispersed both zonally and meridionally by scattering. In the second, waves generated by moving cyclones are shown to be strongly disturbed by scattering, leading again to an increased dispersion.