Idealized hydrodynamic simulations of turbulent oxygen-burning shell convection in 4π geometry
Idealized hydrodynamic simulations of turbulent oxygen-burning shell convection in 4π geometry
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4π 几何中湍流氧燃烧壳对流的理想流体动力学模拟
DOI：
10.1093/mnras/stw2783
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发表时间：
2016
影响因子：
4.8
通讯作者：
Falk Herwig
中科院分区：
文献类型：
--
作者：
Sam Jones;Sam Jones;R. Andrassy;R. Andrassy;S. Sandalski;S. Sandalski;A. Davis;Paul R. Woodward;Paul R. Woodward;Falk Herwig;Falk Herwig
这项工作研究了恒星对流的性质，特别强调了上对流边界（CB）的夹带。理想化的模拟中的O-燃烧壳层的大质量星星的湍流对流进行在$4\pi$几何上的$768^3$和$1536^3$网格，由一个代表性的加热率驱动。还在$768^3$网格上执行加热系列。1536^3 $模拟结果显示，CB上限处的夹带率为1.33\times10 ^{-6}~M_\odot~\mathrm{s}^{-1}$。768^3 $的模拟与相同的加热率在17%内一致。发现对流上边界的卷吸率与驱动光度和上边界剪切速度的立方成线性比例，而径向RMS流体速度与驱动光度的立方根成比例，正如预期的那样。在一维扩散框架中分析混合，从而得到CB混合的简单模型。分析证实了以前的研究结果，即限制MLT混合长度的距离CB在1D模拟更好地代表球平均径向速度分布从3D模拟，并提供了一个改进的确定的参考扩散系数$D_0$的指数扩散CB混合模型在1D。从3D模拟数据，我们采用的对流边界的水平速度分量中的最大梯度的位置，有$2\sigma$的空间波动$\approx0.17 H_P$。指数衰减扩散CB混合模型与$f = 0.03$再现球平均的三维丰度剖面。
This work investigates the properties of convection in stars with particular emphasis on entrainment across the upper convective boundary (CB). Idealised simulations of turbulent convection in the O-burning shell of a massive star are performed in $4\pi$ geometry on $768^3$ and $1536^3$ grids, driven by a representative heating rate. A heating series is also performed on the $768^3$ grid. The $1536^3$ simulation exhibits an entrainment rate at the upper CB of $1.33\times10^{-6}~M_\odot~\mathrm{s}^{-1}$. The $768^3$ simulation with the same heating rate agrees within 17 per cent. The entrainment rate at the upper convective boundary is found to scale linearly with the driving luminosity and with the cube of the shear velocity at the upper boundary, while the radial RMS fluid velocity scales with the cube root of the driving luminosity, as expected. The mixing is analysed in a 1D diffusion framework, resulting in a simple model for CB mixing. The analysis confirms previous findings that limiting the MLT mixing length to the distance to the CB in 1D simulations better represents the spherically-averaged radial velocity profiles from the 3D simulations and provides an improved determination of the reference diffusion coefficient $D_0$ for the exponential diffusion CB mixing model in 1D. From the 3D simulation data we adopt as the convective boundary the location of the maximum gradient in the horizontal velocity component which has $2\sigma$ spatial fluctuations of $\approx0.17 H_P$ . The exponentially decaying diffusion CB mixing model with $f = 0.03$ reproduces the spherically-averaged 3D abundance profiles.