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首页> 外文期刊>Journal of the Atmospheric Sciences >Secondary Instabilities in Breaking Inertia-Gravity Waves
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Secondary Instabilities in Breaking Inertia-Gravity Waves

机译：打破惯性-重力波的次要不稳定性

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摘要

The three-dimensionalization of turbulence in the breaking of nearly vertically propagating inertia gravity waves is investigated numerically using singular vector analysis applied to the Boussinesq equations linearized about three two-dimensional time-dependent basic states obtained from nonlinear simulations of breaking waves: a statically unstable wave perturbed by its leading transverse normal mode, the same wave perturbed by its leading parallel normal mode, and a statically stable wave perturbed by a leading transverse singular vector. The secondary instabilities grow through interaction with the buoyancy gradient and velocity shear in the basic state. Which growth mechanism predominates depends on the time-dependent structure of the basic state and the wavelength of the secondary perturbation. The singular vectors are compared to integrations of the linear model using random initial conditions, and the leading few singular vectors are found to be representative of the structures that emerge in the randomly initialized integrations. A main result is that the length scales of the leading secondary instabilities are an order of magnitude smaller than the wavelength of the initial wave, suggesting that the essential dynamics of the breaking might be captured by tractable nonlinear three-dimensional simulations in a relatively small triply periodic domain.
机译：使用奇异矢量分析对在近似垂直传播的惯性重力波破裂中的湍流进行三维化处理，并将其应用到将Boussinesq方程线性化的三个二维随时间变化的基本状态，该二维状态是根据破裂波的非线性模拟获得的：静态不稳定被其前导横向法向模式所扰动的电磁波，被其前导平行法线模式所扰动的同一波以及被前导横向奇异矢量所扰动的静态稳定波。通过在基本状态下与浮力梯度和速度剪切的相互作用，次级不稳定性会增加。哪种生长机制占主导地位取决于基本状态的时间依赖性结构和二次扰动的波长。使用随机初始条件将奇异矢量与线性模型的积分进行比较，并且发现前几个奇异矢量可以代表随机初始化的积分中出现的结构。主要结果是，领先的次级不稳定性的长度尺度比初始波的波长小一个数量级，这表明断裂的基本动力学可能会通过相对较小的三阶可伸缩非线性三维模拟来捕获周期域。

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