HYDRODYNAMIC SIMULATIONS OF H ENTRAINMENT AT THE TOP OF He-SHELL FLASH CONVECTION
HYDRODYNAMIC SIMULATIONS OF H ENTRAINMENT AT THE TOP OF He-SHELL FLASH CONVECTION
复制标题
氦壳层闪对流顶部 H 夹带的流体力学模拟
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Pei
中科院分区：
文献类型：
--
作者：
P. Woodward;F. Herwig;Pei
本文首次在4π几何结构下对氦壳闪速对流进行了三维完全可压缩气体动力学模拟。这项工作的动机是对后渐近巨星分支（后AGB）恒星（樱井天体）和金属匮乏的AGB恒星中h摄取闪光的观察结果理解不足。我们的研究主要集中在顶部对流边界的夹带过程以及随后富h物质向更深层的平流，因此我们在本研究中忽略了富质子燃料的燃烧。我们发现，在我们的深对流区，近全球尺度的相干对流运动似乎占主导地位。在顶边界处，对流切变流相对于开尔文-亥姆霍兹不稳定性是稳定的。然而，这种剪切不稳定性是由大尺度、反向流动中的边界层分离引起的。这将厚壳对流的全局性质与夹带过程联系起来。我们建立了夹带率对网格分辨率的定量依赖关系。使用我们的数值技术，需要10243个或更多单元的模拟才能达到适合此问题的数值保真度。然而，只有15363模拟的结果清楚地表明，我们在夹带率方面接近收敛。我们的结果表明，我们的方法，详细描述，可以提供定量的结果，有关夹带和对流边界混合在深恒星内部环境非常硬的对流边界。对于我们详细研究的代表性案例，我们发现夹带率为4.38±1.48 × 10−13 M☉s−1。
We present the first three-dimensional, fully compressible gas-dynamics simulations in 4π geometry of He-shell flash convection with proton-rich fuel entrainment at the upper boundary. This work is motivated by the insufficiently understood observed consequences of the H-ingestion flash in post-asymptotic giant branch (post-AGB) stars (Sakurai's object) and metal-poor AGB stars. Our investigation is focused on the entrainment process at the top convection boundary and on the subsequent advection of H-rich material into deeper layers, and we therefore ignore the burning of the proton-rich fuel in this study. We find that for our deep convection zone, coherent convective motions of near global scale appear to dominate the flow. At the top boundary convective shear flows are stable against Kelvin–Helmholtz instabilities. However, such shear instabilities are induced by the boundary-layer separation in large-scale, opposing flows. This links the global nature of thick shell convection with the entrainment process. We establish the quantitative dependence of the entrainment rate on grid resolution. With our numerical technique, simulations with 10243 cells or more are required to reach a numerical fidelity appropriate for this problem. However, only the result from the 15363 simulation provides a clear indication that we approach convergence with regard to the entrainment rate. Our results demonstrate that our method, which is described in detail, can provide quantitative results related to entrainment and convective boundary mixing in deep stellar interior environments with very stiff convective boundaries. For the representative case we study in detail, we find an entrainment rate of 4.38 ± 1.48 × 10−13 M☉ s−1.
影响因子：
3.5
作者：
K. Werner;F. Herwig
通讯作者：
K. Werner;F. Herwig