Wani Rauoof, Mir Ajaz, Batool Farida, Tiwari Sanat
Department of Physics, Indian Institute of Technology Jammu, Jammu, 181221, India.
Sci Rep. 2022 Jul 7;12(1):11557. doi: 10.1038/s41598-022-15725-2.
Rayleigh-Taylor instability (RTI) is the prominent energy mixing mechanism when heavy fluid lies on top of light fluid under the gravity. In this work, the RTI is studied in strongly coupled plasmas using two-dimensional molecular dynamics simulations. The motivation is to understand the evolution of the instability with the increasing correlation (Coulomb coupling) that happens when the average Coulombic potential energy becomes comparable to the average thermal energy. We report the suppression of the RTI due to a decrease in growth rate with increasing coupling strength. The caging effect is expected a physical mechanism for the growth suppression observed in both the exponential and the quadratic growth regimes. We also report that the increase in shielding due to background charges increases the growth rate of the instability. Moreover, the increase in the Atwood number, an entity to quantify the density gradient, shows the enhancement of the growth of the instability. The dispersion relation obtained from the molecular dynamics simulation of strongly coupled plasma shows a slight growth enhancement compared to the hydrodynamic viscous fluid. The RTI and its eventual impact on turbulent mixing can be significant in energy dumping mechanisms in inertial confinement fusion where, during the compressed phases, the coupling strength approaches unity.
瑞利 - 泰勒不稳定性（RTI）是在重力作用下重流体位于轻流体之上时的主要能量混合机制。在这项工作中，使用二维分子动力学模拟在强耦合等离子体中研究了RTI。其动机是了解随着平均库仑势能变得与平均热能相当而发生的相关性（库仑耦合）增加时不稳定性的演化。我们报告了由于随着耦合强度增加增长率降低而导致的RTI抑制。笼效应被认为是在指数增长和二次增长区域中观察到的增长抑制的一种物理机制。我们还报告了由于背景电荷导致的屏蔽增加会提高不稳定性的增长率。此外，阿特伍德数（一个用于量化密度梯度的量）的增加表明不稳定性增长的增强。从强耦合等离子体的分子动力学模拟获得的色散关系显示，与流体动力学粘性流体相比，有轻微的增长增强。在惯性约束聚变的能量沉积机制中，RTI及其最终对湍流混合的影响可能很显著，在压缩阶段，耦合强度接近1。
