Kinetic interpretation of the classical Rayleigh-Taylor instability
Kinetic interpretation of the classical Rayleigh-Taylor instability
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经典瑞利-泰勒不稳定性的动力学解释
DOI：
10.1103/physreve.105.065209
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发表时间：
2022
影响因子：
2.4
通讯作者：
Srinivasan, Bhuvana
中科院分区：
文献类型：
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作者：
Rodman, John;Cagas, Petr;Hakim, Ammar;Srinivasan, Bhuvana
瑞利-泰勒（RT）不稳定性普遍存在于从天体物理到实验室等离子体的许多物理状态中，主要使用流体模型进行研究，其中大多数是理想流体模型。本文采用连续动力学模型进行了五维（两个空间维度，三个速度空间维度）模拟，研究了碰撞平均自由程和输运对不稳定性增长的影响。连续动力学模型提供了对完整粒子分布函数的无噪声访问，允许对动力学物理在流体动力学现象（如RT不稳定性）中的作用进行详细研究。对于长平均自由程，没有RT不稳定性增长，但随着碰撞的增加，粒子向麦克斯韦速度分布松弛，动力学模拟再现了流体模拟结果。这项工作的一个重要的和新颖的贡献是在中间碰撞的情况下，不能与传统的流体模型和需要动力学建模。中等碰撞情况的模拟表明，与高度碰撞的流体情况相比，RT不稳定演化有显著改变。具体而言，中碰撞RT不稳定性的增长速度低于高碰撞情况，同时也产生了明显更扩散的界面。在RT不稳定界面的演化过程中，相对于惯性项，分布函数的高矩对中间碰撞的作用更大。粒子能量通量由分布的矩计算得到，表明输运在中间碰撞情况下发生了显著变化，并且更偏离流体状态的高碰撞极限。
Rayleigh-Taylor (RT) instabilities are prevalent in many physical regimes ranging from astrophysical to laboratory plasmas and have primarily been studied using fluid models, the majority of which have been ideal fluid models. This work presents a five-dimensional (two spatial dimensions, three velocity space dimensions) simulation using the continuum-kinetic model to study the effect of the collisional mean free path and transport on the instability growth. The continuum-kinetic model provides noise-free access to the full particle distribution function permitting a detailed investigation of the role of kinetic physics in hydrodynamic phenomena such as the RT instability. For long mean free path, there is no RT instability growth, but as collisionality increases, particles relax towards the Maxwellian velocity distribution, and the kinetic simulations reproduce the fluid simulation results. An important and novel contribution of this work is in the intermediate collisional cases that are not accessible with traditional fluid models and require kinetic modeling. Simulations of intermediate collisional cases show that the RT instability evolution is significantly altered compared to the highly collisional fluidlike cases. Specifically, the growth rate of the intermediate collisionality RT instability is lower than the high collisionality case while also producing a significantly more diffused interface. The higher moments of the distribution function play a more significant role relative to inertial terms for intermediate collisionality during the evolution of the RT instability interface. Particle energy flux is calculated from moments of the distribution and shows that transport is significantly altered in the intermediate collisional case and deviates much more so from the high collisionality limit of the fluid regime.