Convective overshooting and penetration in a Boussinesq spherical shell
Convective overshooting and penetration in a Boussinesq spherical shell
复制标题
Boussinesq 球壳中的对流过冲和穿透
DOI：
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发表时间：
2018
影响因子：
4.8
通讯作者：
N. Brummell
中科院分区：
文献类型：
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作者：
Lydia Korre;P. Garaud;N. Brummell
作者(S)：Korre，L；Garaud，P；Brummell，NH|摘要：我们研究了湍流对流运动从对流区(CZ)延伸到位于后者下方的稳定区(RZ)的动力学。为此，我们在球壳几何中进行了一系列三维直接数值模拟求解Boussinesq近似下的Navier-Stokes方程。我们观察到，湍流运动进入稳定层结区的超调取决于三个不同的参数：RZ的相对稳定性、两者之间的过渡宽度和湍流的强度。在所研究的情况下，这些运动设法部分改变了热层结并诱导热混合，但不是如此有效地将标称CZ进一步向下延伸到稳定区。我们发现，对流区以下的动能可以用半高斯分布来模拟，其幅度和宽度都可以在所有模拟中预先预测。我们研究了与运动延伸到RZ的深度有关的不同的动力学长度尺度，我们发现它们都非常好地标度了源于一个简单的能量论证的长度尺度。我们讨论了我们的发现对一维恒星演化计算的影响。
Author(s): Korre, L; Garaud, P; Brummell, NH | Abstract: We study the dynamics associated with the extension of turbulent convective motions from a convection zone (CZ) into a stable region (RZ) that lies below the latter. For that purpose, we have run a series of three-dimensional direct numerical simulations solving the Navier-Stokes equations under the Boussinesq approximation in a spherical shell geometry. We observe that the overshooting of the turbulent motions into the stably stratified region depends on three different parameters: the relative stability of the RZ, the transition width between the two, and the intensity of the turbulence. In the cases studied, these motions manage to partially alter the thermal stratification and induce thermal mixing, but not so efficiently as to extend the nominal CZ further down into the stable region. We find that the kinetic energy below the convection zone can be modeled by a half-Gaussian profile whose amplitude and width can be predicted a priori for all of our simulations. We examine different dynamical lengthscales related to the depth of the extension of the motions into the RZ, and we find that they all scale remarkably well with a lengthscale that stems from a simple energetic argument. We discuss the implications of our findings for 1D stellar evolution calculations.