A theory of non-local mixing-length convection - III. Comparing theory and numerical experiment
A theory of non-local mixing-length convection - III. Comparing theory and numerical experiment
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DOI：
10.1093/mnras/279.2.305
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发表时间：
1995-09
影响因子：
4.8
通讯作者：
S. Grossman
中科院分区：
文献类型：
--
作者：
S. Grossman
我们求解非局部对流方程。四个模型问题的解决方案进行了比较GSPH模拟的结果。在每种情况下，我们测试两个封闭方案：1）其中三阶矩定义的扩散近似;和2）其中使用完整的三阶矩方程和四阶矩定义的准正规近似的修改形式。在过冲模式中，对流通量在稳定边界后不久变为负值。负振幅很小，超调区的温度梯度接近辐射值。湍流速度在$0.5$-$1.5\ell$之后衰减$e$，这取决于模型，其中$\ell$是混合长度。湍流粘性比负浮力在减速过冲液滴方面更重要。这些预测与日震学一致。
We solve the nonlocal convection equations. The solutions for four model problems are compared with results of GSPH simulations. In each case we test two closure schemes: 1) where third moments are defined by the diffusion approximation; and 2) where the full third moment equations are used and fourth moments are defined by a modified form of the quasi-normal approximation. In overshooting models, the convective flux becomes negative shortly after the stability boundary. The negative amplitude remains small, and the temperature gradient in the overshooting zone has nearly the radiative value. Turbulent velocities decay by a factor of $e$ after $0.5$--$1.5\ell$, depending on the model, where $\ell$ is the mixing length. Turbulent viscosity is more important than negative buoyancy in decelerating overshooting fluid blobs. These predictions are consistent with helioseismology.