恒星对流的Reynolds应力模型及其日震学检验
文献类型：学位论文
| 作者 | 杨家艳 |
| 学位类别 | 博士 |
| 答辩日期 | 2006-12-21 |
| 授予单位 | 中国科学院研究生院（云南天文台） |
| 授予地点 | 北京 |
| 导师 | 李焱 |
| 关键词 | 湍流对流模型 太阳内部结构 太阳对流区 日震学 |
| 其他题名 | Reynolds stress model and its helioseismological testing |
| 学位专业 | 天体物理 |
| 中文摘要 | 如何处理恒星中的对流运动，是恒星结构和演化理论中一个极为重要的问题。在本论文中，我们从流体力学基本方程组出发，建立了一个描述湍流对流运动的Reynolds应力模型，并将它用于太阳模型中，对这一对流模型以及其中的自由参数进行了充分的检验和限制。我们的主要目的是要检验一些在混合长理论中被忽略了的物理过程，例如湍流的耗散、扩散以及各向异性等，对太阳对流区结构的影响；同时，也希望通过与日震观测结果的对比，获得Reynolds应力模型中的自由参数在天体物理条件下的取值情况的有关信息。 研究发现，Reynolds应力模型得到的对流能量流通常比混合长模型的结果更大，并且传能效率敏感地依赖于对流模型中的耗散系数。湍流的扩散效应对太阳对流区的结构有很重要的影响，它使得对流区内各个Reynolds关联量的轮廓明显地被降低和展宽，使得超绝热对流区内的温度梯度明显增大，而在对流区边界附近的温度梯度有所减小。与采用混合长理论的标准太阳模型相比，采用我们的Reynolds应力模型的太阳模型的整体结构如温度、绝热声速等发生了很小的变化，但这种小变化却是非常有意义的。 借助日震学的观测结果，我们在太阳内部测定了Reynolds应力模型中涉及到的自由参数的取值情况。研究发现，如果适当选取自由参数的值，则不论是采用局地还是非局地Reynolds应力模型的太阳模型都可以得到比标准太阳模型更符合观测结果的理论振动频率。减小耗散系数Ct和Ce的值以及增大扩散系数Ct1和Ce1的值可以减小理论计算频率，使之更符合观测值，而参数Ck和Cs的值则对理论计算频率没有明显影响。我们还发现，理论频率发生改变的根本原因在于，湍流的耗散过程和扩散过程改变了对流区内的温度分布。如果将六个自由参数都取较好的值（即较小的耗散系数和较大的扩散系数），采用我们的Reynolds应力模型的太阳模型可以将中、高阶p模式振动的理论频率与观测频率之间的差距减小约30﹪。这一结果对太阳模型的研究有一定的参考价值，它提示我们在太阳模型中考虑湍流对流将有助于得到更符合观测结果的p模式理论振动频率。 |
| 英文摘要 | How to deal with the turbulent convection motion in stars is a very important problem in the theory of stellar structure and evolution. A Reynolds stress model based on hydrodynamic moment equations was established and applied to the solar model. The convection model and the free parameters involved in the model are tested and determined in the solar interior. The aim is to test the effects of some physical processes on the structure of the solar convection zone, such as the dissipation, diffusion, and anisotropy of turbulence that have been ignored in the classical mixing-length theory (MLT). Free parameters introduced by the Reynolds stress model are also tested with the aid of helioseismology in order to find appropriate values for astrophysical applications. It is found that, the Reynolds stress models usually give larger convective heat fluxes than the MLT does, and the heat transport efficiency is sensitively related to the dissipation parameters used in the Reynolds stress models. The turbulent diffusion is found to have important effects on the structure of the solar convection zone. It leads to significantly lowered and expanded profiles for the Reynolds correlations, and a larger temperature gradient in the central part of the super-adiabatic convection region but a small one near the boundaries of the convection zone. Solar models with our Reynolds stress model give small but meaningful differences in the global structure such as temperature and sound speed compared with the standard solar model using the MLT. The free parameters involved in the Reynolds stress model are determined in the solar interior with the aid of helioseismology. It is found that, with appropriate choices of the turbulent parameters, solar model with both local and non-local Reynolds stress model can give the calculated p-mode frequencies in better consistent with the observations than the standard solar model does. Decreasing the values of dissipation parameters Ct and Ce or increasing the values of diffusion parameters Ct1 and Ce1 helps to reduce the calculated frequencies, while the parameters Ck and Cs have no obvious effect on the p-mode frequencies. The temperature in the convection zone is changed due to the dissipation and diffusion of the turbulence. It is just this temperature difference that makes the calculated frequencies changed. Combined better values of the free parameters, solar models with our Reynolds stress model can reduce the frequency differences between the model calculations and observation as much as 30 percent for the modes of middle and high l. This result can give a clue to solar modeling, that is, including turbulence in solar models is helpful to reproduce the observed solar p-mode frequencies. |
| 学科主题 | 天文学 |
| 语种 | 中文 |
| 页码 | 113 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/5319]  |
| 专题 | 云南天文台_恒星物理研究组 |
| 推荐引用方式 GB/T 7714 | 杨家艳. 恒星对流的Reynolds应力模型及其日震学检验[D]. 北京. 中国科学院研究生院（云南天文台）. 2006. |
入库方式： OAI收割
来源：云南天文台
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