引力不稳引起角动量传输的不同模型对原行星盘结构的影响

发布时间：2018-01-11 20:38

本文关键词：引力不稳引起角动量传输的不同模型对原行星盘结构的影响　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：环绕恒星的盘子的形成是从分子云核塌缩开始的。塌缩持续过程中，由压力支撑的恒星在向内流动的中心处形成，同时拥有更高角动量的下落物质在恒星周围形成环绕恒星的盘状结构。原恒星就是由中央恒星和盘子系统所构成的。大质量的盘子很容易产生引力不稳定性，引力力矩引起盘子角动量由内向外传递的效果与粘滞力传递角动量机制很相似，所以LinPringle (1987,1990)提出了“引力不稳粘滞”的概念。引力不稳粘滞模型在原行星盘的形成与演化模拟中非常适用。但它只是一种方便处理，本质上并不是一种粘滞力。引力不稳粘滞在恒星形成中起重要作用，天体物理工作者对于它的研究也不断深入。他们提出了多种引力不稳粘滞模型，这些模型基于不同的原理而有不同的形式。我们的目的就是将不同粘滞形式放在一起进行模拟，然后对模拟结果进行比较和分析。这对天体研究有重要的意义。本论文第一章对研究背景作简单描述，第二章按时间顺序给出不同引力不稳粘滞模型的原理、粘滞表达式、应用和产生的结果等详细处理过程，第三章中我们选择最典型的四种引力不稳模型，，代入初始条件相同的同一个恒星形成与演化模型中，对得到的结果进行详细分析和比较，来讨论不同引力不稳模型对原行星盘结构的影响。最后在第四章对我们的工作做总结和展望。根据四种不同引力不稳粘滞模型产生的数据结果，我们画出了对应的不稳定性参量Q、粘滞系数和面密度在盘子中的径向分布，并对它们进行分析和对比。我们对比四种模型在盘子形成和演化不同时刻结构的变化，也对比了同一时刻这三种不同参量的相互关联，以及同一时刻同一参量不同模型之间的差别，并给出相应的分析和解释。我们发现三种不同函数形式的引力不稳粘滞模型（Kratter模型，LinPringle模型和Zhu的指数模型）对原行星盘结构的影响是一致的，盘子中面密度径向分布曲线几乎重合。而引力不稳定时（Q1），对整个盘子取常数引力不稳粘滞值为0.02的模型(JinLi模型)，与另外三种模型产生的结果会有不同。直到盘子演化中晚期，四种模型对应盘子面密度分布曲线及粘滞分布曲线才逐渐趋于重合。因此我们得到结论，对引力不稳粘滞在盘子中进行分段（局部）取函数值，会产生平滑、连续的面密度和粘滞分布曲线。这些引力不稳粘滞模型在盘子形成和演化不同时间和半径位置产生的面密度分布曲线基本重合，对原行星盘结构的影响比较接近。而引力不稳定时对整个盘子取常数粘滞值的模型，盘子中粘滞分布曲线断层明显，没有一个缓和的连接。因而引起面密度分布曲线不够平滑。这此结论在原行星盘形成和演化模拟研究中，对于引力不稳定粘滞模型的选取和处理有很大的参考价值。
[Abstract]:The plate forming around the star begins with the collapse of the molecular cloud nucleus. During the process of collapse, the pressurized star forms at the center of the inward flow. At the same time falling matter with higher angular momentum forms a disk structure around the star. The protostar is made up of the central star and the plate system. It is easy to produce gravitational instability in a plate with large mass. The effect of gravitational moment on angular momentum transfer from inside to out is similar to that of viscous force transfer. So LinPringle 1987. In 1990, the concept of "gravitational instability viscosity" was put forward. The gravitational instability viscosity model is very suitable for the formation and evolution of the original planetary disk, but it is only a convenient way to deal with it. Essentially, it is not a viscous force. Gravitational instability viscosity plays an important role in star formation and has been studied deeply by astrophysicists. They have proposed a variety of gravitational instability viscosity models. These models have different forms based on different principles. Our aim is to simulate different viscous forms together. Then the simulation results are compared and analyzed, which is of great significance to the study of celestial bodies. The first chapter of this paper gives a brief description of the research background. The second chapter gives the principle of different gravitational instability viscosity model, viscous expression, application and the results of the detailed processing process according to the time order. In the third chapter, we choose the most typical four kinds of gravitational instability model, and substitute the same star formation and evolution model with the same initial conditions, and analyze and compare the obtained results in detail. The effects of different gravitational instability models on the structure of the original planetary disk are discussed. Finally, our work is summarized and prospected in Chapter 4th. Based on the data obtained from four different gravitational instability models, the radial distributions of the corresponding instability parameters Q, viscosity coefficient and surface density in the plate are drawn. We compare the structural changes of the four models at different times of plate formation and evolution, and also compare the correlation of these three different parameters at the same time. And the differences between different models of the same parameter at the same time, and the corresponding analysis and explanation are given. We find three different forms of gravitational instability viscosity model and Kratter model. The influence of LinPringle model and Zhu's exponential model on the structure of the original planetary disk is consistent. The radial distribution curve of the surface density of the plate almost coincides with that of the plate. The JinLi model with a constant gravitational instability of 0.02 for the whole plate will produce different results from the other three models until the middle and late stage of plate evolution. The four models correspond to the plate surface density distribution curve and the viscous distribution curve. Therefore, we conclude that the piecewise (local) function of the gravitational instability in the plate will produce smoothness. Continuous surface density and viscosity distribution curves. The surface density distribution curves generated by these gravitational instability viscosity models at different time and radius positions of plate formation and evolution are basically coincident with each other. The influence on the structure of the original planetary disk is close, but the viscous curve fault of the plate is obvious when the gravitational instability takes the constant viscosity value for the whole plate. There is no moderate connection, which results in the surface density distribution curve being not smooth enough. This conclusion has been studied in the study of the formation and evolution of the original planetary disk. It has great reference value for the selection and treatment of gravitational instability viscosity model.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P144

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