对流不稳定剪切流中的Angular momentum输运
Angular momentum transport in convectively unstable shear flows
摘要：
采用剪切盒近似，对流体动力湍流对流引起的角动量输运进行了局部三维数值模拟。我们确定的湍流粘度从非旋转运行的剪切参数的值的范围内，并使用一个简单的分析模型，以提取非扩散的贡献（λ效应）的旋转包括在运行中的应力。我们的研究结果表明，湍流粘度的混合长度估计的顺序和弱旋转的影响。λ效应是非零的，并且比慢旋转状态中的湍流粘度小2-4倍。我们表明，开普勒剪切，角动量输运可以改变符号和向外旋转周期大于周转时间时，即当科里奥利数是低于1。这个结果似乎与瑞利数的值相对无关。
英文摘要：
Angular momentum transport owing to hydrodynamic turbulent convection is studied using local three dimensional numerical simulations employing the shearing box approximation. We determine the turbulent viscosity from non-rotating runs over a range of values of the shear parameter and use a simple analytical model in order to extract the non-diffusive contribution (Lambda-effect) to the stress in runs where rotation is included. Our results suggest that the turbulent viscosity is of the order of the mixing length estimate and weakly affected by rotation. The Lambda-effect is non-zero and a factor of 2-4 smaller than the turbulent viscosity in the slow rotation regime. We demonstrate that for Keplerian shear, the angular momentum transport can change sign and be outward when the rotation period is greater than the turnover time, i.e. when the Coriolis number is below unity. This result seems to be relatively independent of the value of the Rayleigh number.
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