Investigation of strong isothermal stratification effects on multi-mode compressible Rayleigh–Taylor instability
Investigation of strong isothermal stratification effects on multi-mode compressible Rayleigh–Taylor instability
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DOI：
10.1063/5.0164504
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发表时间：
2023-08
影响因子：
4.6
通讯作者：
Denis Aslangil;Man Long Wong
中科院分区：
文献类型：
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作者：
Denis Aslangil;Man Long Wong
当密度梯度和加速度方向相反时，瑞利-泰勒不稳定性 (RTI) 发生在分离两种承受加速度的流体的界面处。先前的科学研究主要在不可压缩假设下考虑RTI，这在许多高能量密度工程应用和天体物理现象中可能并不成立。在这项研究中，使用完全可压缩的多物种直接数值模拟探讨了背景等温分层强度对多模式二维 RTI 的可压缩性影响。研究了三种不同等温马赫数（Ma=0.15、0.3 和 0.45）下的情况，以分别探索阿特伍德数为 0.04 时的弱、中和强分层可压缩 RTI。与不可压缩的 RTI 不同，通过背景分层的强度增加流动压缩性可以抑制 RTI 的生长，并可以导致 RTI 混合层生长终止于高分子混合状态。我们的研究结果表明，即使在选择相对较低的阿特伍德数时，由于可压缩 RTI 的背景分层增加，可变密度效应也可以显着增强，因为对于强分层情况，不同的空间分布在混合层上变得明显不对称。此外，本研究通过研究湍流动能的传输以及涡动力学来比较案例的混沌行为。还使用三种不同的雷诺数检查了结果的雷诺数依赖性，并且对于感兴趣的大规模混合和流动量的发现被证明在所研究的雷诺数范围内是普遍的。
Rayleigh–Taylor instability, RTI, occurs at the interface separating two fluids subjected to acceleration when the density gradient and the acceleration are in opposite directions. Previous scientific research primarily considered RTI under the incompressible assumption, which may not be valid in many high-energy-density engineering applications and astrophysical phenomena. In this study, the compressibility effects of the background isothermal stratification strength on multi-mode two-dimensional RTI are explored using fully compressible multi-species direct numerical simulations. Cases under three different isothermal Mach numbers – Ma=0.15, 0.3, and 0.45 – are investigated to explore weakly, moderately, and strongly stratified compressible RTI, respectively, at an Atwood number of 0.04. Unlike incompressible RTI, an increase in the flow compressibility through the strength of the background stratification can suppress the RTI growth and can lead to a termination of the RTI mixing layer growth with a highly molecularly mixed state. Our findings suggest that even at the chosen relatively low Atwood number, the variable-density effects can be significantly enhanced due to an increase in the background stratification for the compressible RTI as different spatial profiles become noticeably asymmetric across the mixing layer for the strongly stratified case. In addition, this study compares the chaotic behavior of the cases by studying the transport of the turbulent kinetic energy as well as the vortex dynamics. The Reynolds number dependence of the results is also examined with three different Reynolds numbers, and the findings for the large-scale mixing and flow quantities of interest are shown to be universal in the range of the Reynolds numbers studied.