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arXiv 0803.3264physics.ao-phphysics.comp-ph
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声重力波Turbulence的频谱特性

Spectral Properties of Acoustic Gravity Wave Turbulence

Dastgeer Shaikh, Padma K Shukla, Lennart Stenflo

摘要:

采用二维非线性流体模拟方法研究了声重力波之间的非线性湍流相互作用。声重力波由速度扰动和密度扰动组成,在地球大气中沿垂直方向穿过密度梯度传播。我们发现,耦合的两个组件模型显示出沿垂直方向的大规模速度势流的产生,而密度扰动松弛向各向同性的随机分布。与系统相关的特征湍流谱具有Kolmogorov特征,并倾向于向$k^{-5/3}$谱松弛,其中$k$是典型的波数。与速度势相关的交叉场扩散线性增长,并在非线性阶段饱和。

英文摘要:

The nonlinear turbulent interactions between acoustic gravity waves are investigated using two dimensional nonlinear fluid simulations. The acoustic gravity waves consist of velocity and density perturbations and propagate across the density gradients in the vertical direction in the Earth's atmosphere. We find that the coupled two component model exhibits generation of large scale velocity potential flows along the vertical direction, while the density perturbations relax towards an isotropic random distribution. The characteristic turbulent spectrum associated with the system has a Kolmogorov-like feature and tends to relax towards a $k^{-5/3}$ spectrum, where $k$ is a typical wavenumber. The cross field diffusion associated with the velocity potential grows linearly and saturates in the nonlinear phase.

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