Collaborative Research: Multidimensional hydrodynamic studies of convection and mixing in stars, novae, and supernovae

该项目建立在最近的突破，在完全三维可压缩，多流体，湍流对流模拟。对流几乎是绝热的（高佩克莱特数），这是恒星中几乎所有对流的典型特征（除了靠近恒星表面的部分），并且一直计算到它进入准静态湍流稳定状态。这使得理论分析，表明如何改善传统的方法来模拟对流（混合长度理论）。这也说明了混合长度理论是如何运作得足够好，能够存活半个世纪的。这些新结果适用于恒星演化的几乎所有阶段。一个新的特征是湍流夹带，这在气象学，海洋学和地球实验中是众所周知的，但以前没有应用于恒星的演化。三维模拟指向一个更简单的恒星对流物理学，这是被纳入恒星演化代码制定。在这里，三个具体的项目将由阿内特博士和斯塔尔菲尔德进行：（1）重新计算恒星演化，从恒星诞生到死亡，形成超新星或白色矮星，包括夹带和旋转，（2）扩展3D模拟，以在不同的物理条件下测试这些新想法，包括旋转的影响，（3）利用经典新星的大量观测资料作为对流和剪切混合的理论试验台。扩展到经典新星，既包括热核逃逸之前的混合，也包括逃逸过程中的混合。几个突出的问题将使用新的方法，包括太阳丰度问题和日震学，混合在经典新星，从大质量恒星的同位素产量，混合在第一个恒星及其对产量的影响，在超新星祖先的非球形行为，和太阳模拟的成分梯度的影响。这里开发的恒星演化软件和输入数据将在一个网站上免费提供，供高级学生、教师和其他科学家使用，还有一套用于模拟核心坍缩和热核超新星爆炸以及新星的多维祖先模型。此外，样品演化序列（从0.7到200太阳质量）和同位素产量将可用于银河系演化建模和陨石研究。太阳能对流区的底部的模拟建议，这应该有助于扩展的滞弹性方法来处理非均匀流体。国家点火装置的激光实验目标设计将使用该项目的模拟来测试超新星1987 A的混合模型。

This project builds upon a recent breakthrough in the simulation of fully three-dimensional compressible, multifluid, turbulent convection. The convection is nearly adiabatic (high Peclet number), typical of almost all convection in stars (except near the stellar surface), and is calculated until it settles into a quasi-static turbulent steady state. This allows theoretical analysis which shows how to improve the conventional approach to modeling convection (mixing-length theory). It also shows how mixing-length theory could have worked well enough to survive for a half-century. The new results are applicable to almost all stages of stellar evolution. A new feature is turbulent entrainment, which is well known in meteorology, oceanography, and terrestrial experiments, but has not been previously applied to the evolution of stars. The three-dimensional simulations point to a simpler formulation of the stellar convection physics which is being incorporated into stellar evolutionary codes. Here, three specific projects will be undertaken by Drs. Arnett and Starrfield: (1) a recalculation of stellar evolution, from stellar birth to death with the formation of a supernova or a white dwarf, including entrainment and rotation, (2) an extension of the 3D simulations to test these new ideas in different physical conditions, including the effect of rotation, and (3) use of the extensive observational data on classical novae as a theoretical test bed for convective and shear mixing. Extension to classical novae involves both the mixing prior to the thermonuclear runaway and the mixing during the runaway itself. Several outstanding problems will be addressed using the new methods, including the solar abundance problem and helioseismology, mixing in classical novae, isotopic yields from massive stars, mixing in the first stars and its effect on yields, nonspherical behavior in supernova progenitors, and the effect of compositional gradients on solar simulations. The software for stellar evolution developed here and the input data, will be freely available on a website for use by advanced students, teachers, and other scientists, as will a set of multidimensional progenitor models for simulation of core collapse and thermonuclear supernova explosions, and novae. In addition, sample evolutionary sequences (from 0.7 to 200 Solar masses) and isotopic yields will be available for use in galactic evolutionary modeling and for meteoritic studies. Simulations of the bottom of the solar convection zone are proposed which should aid the extension of anelastic methods to deal with nonhomogeneous fluids. Target design for laser experiments at the National Ignition Facility will use simulations from this project to test mixing models for Supernova 1987A.