ANGULAR MOMENTUM TRANSPORT IN CONVECTIVELY UNSTABLE SHEAR FLOWS
ANGULAR MOMENTUM TRANSPORT IN CONVECTIVELY UNSTABLE SHEAR FLOWS
复制标题
对流不稳定剪切流中的角动量输运
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
R. Narayan
中科院分区：
文献类型：
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作者：
P. Käpylä;A. Brandenburg;M. Korpi;J. Snellman;R. Narayan
采用剪切盒近似的局部三维数值模拟方法，研究了流体动力湍流对流的角动量输运问题。我们在剪切参数值的范围内确定了非旋转游程的湍流粘度，并使用一个简单的分析模型来提取包含旋转的游程中对应力的非扩散贡献(Λ效应)。我们的结果表明，湍流粘性在混合长度估计的数量级上，并且受旋转的影响很小。在慢旋区，Λ效应不为零，比湍流粘性小2-4倍。我们证明了对于开普勒切变，当自转周期大于翻转时间，即当科里奥利数小于1时，角动量输运可以变号并向外运动。这一结果似乎相对独立于瑞利数的值。
Angular momentum transport due 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 (Λ-effect) to the stress in runs where rotation is included. Our results suggest that the turbulent viscosity is on the order of the mixing length estimate and weakly affected by rotation. The Λ-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.