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Nonlinear Evolution of two Gravitational Instabilities and Thermal Conduction Loss at Fractal Interface

分形界面处两种引力不稳定性和热传导损失的非线性演化

基本信息

批准号：
11680486
负责人：
NISHIHARA Katsunobu
金额：
$ 2.37万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

1. We have developed a weakly nonlinear theory of ablative Rayleigh-Taylor (RT) instability with a finite bandwidth Included self-consistently. The theory includes up to third order nonlinearity that results in saturation of linear growth and determines weakly nonlinear growth. It is found that the ablation effects reduce both the saturation amplitude of the linear growth and the weakly nonlinear growth. They are evaluated for plastic and DT targets. The weakly nonlinear growth is shown given by the product pf the linear growth and the saturation amplitude.2. A third order nonlinear theory of Richtmyer-Meshkov (RM) instability has been developed by treating unstable interface as a vortex sheet with density jump. Nonlinear growth rates of spike and bubble are shown to agree well with hydrodynamic simulations. Circulation varies locally with time due to the density jump at the sheet and it introduces stretching and shrinking of the interface locally.3. We have developed a molecular dynamic simulation program to treat RM instability in a cylindrical geometry, that conventional hydrodynamic codes fails to simulate. With the use of the code, we have investigated the stability of converging shocks and the nonlinear growth of RM instability, We have shown the increase of the nonlinear growth due to multiple shocks rebounded at the center and its dependence on mode number.4. We have developed self-similar solutions of laser implosion in which thermal conduction plays an important rote by using Lie group theory. This model has been applied for hydrodynamically equivalent implosions in order to design future experimental facility for ignition and high gain in inertial fusion energy research.

1. 我们提出了一个有限带宽包含自洽的烧蚀瑞利-泰勒（RT）不稳定性的弱非线性理论。该理论包括高达三阶非线性，导致线性增长饱和，并确定弱非线性增长。结果表明，烧蚀作用降低了线性生长和弱非线性生长的饱和幅值。它们被评估为塑料和DT目标。弱非线性增长由线性增长与饱和幅值的乘积表示。将不稳定界面看作具有密度跳变的涡流片，提出了一种三阶非线性richmyer - meshkov （RM）不稳定性理论。峰状和气泡的非线性生长速率与水动力模拟结果吻合较好。由于薄板上的密度跳跃，循环局部随时间变化，并在局部引入了界面的拉伸和收缩。我们开发了一个分子动力学模拟程序来处理圆柱形几何中的RM不稳定性，传统的流体动力学代码无法模拟。利用程序研究了收敛冲击的稳定性和RM不稳定性的非线性增长，证明了在中心反弹多重冲击时非线性增长的增加及其与模态数的依赖关系。利用李群理论，我们得到了热传导起重要作用的激光内爆自相似解。该模型已应用于流体动力等效内爆实验，为今后在惯性聚变能研究中设计点火和高增益实验装置提供了参考。