Numerous studies have elaborated the dominated roles of Kelvin-Helmholtz instability (KHI) and Rayleigh-Taylor instability (RTI) in the liquid sheet breakup and primary atomization. As for applications in aeronautics, the liquid-gas mixing generally occurs at the challenging conditions of a large density ratio and high Reynolds number. Hence, the evaluation of KHI and RTI under such challenging conditions will have great significance in better understanding the destabilizing mechanism of the liquid layer. To this end, a lattice Boltzmann multiple-relaxation-time (MRT) two-phase model, based on the conservative Allen-Cahn equation, is reconstructed for the present study. Preliminarily, the numerical stability and accuracy of this MRT model are tested by Laplace’s law under a large density ratio and high Reynolds number, including the sensitivity study to the values of mobility. Afterward, KHI and RTI are investigated in wide ranges of the Reynolds number, density ratio, and viscosity ratio. Numerical results indicate that the enhanced viscous force of light fluid with an increasing viscosity ratio notably suppresses the roll-ups of heavy fluid in KHI and RTI. As for the density ratio, it generally shows negative impacts on fluid-mixing in KHI and spike-spiraling in RTI. However, when the density ratio and the Reynolds number both arrive at high levels, the Kelvin-Helmholtz wavelets aroused by a dominated inertia force of heavy fluid trigger severe interface disintegration. The above results once more demonstrate the excellent ability of the present model in dealing with challenging conditions. Besides, the morphological characteristics of KHI and RTI at a high Reynolds number and large density ratio also greatly support the typical interface breakup mechanism observed in primary atomization.

中文翻译：

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在较大的密度比，粘度比和雷诺数范围内对KHI和RTI进行基于相场的LBM分析

许多研究已经详细阐述了Kelvin-Helmholtz不稳定性（KHI）和Rayleigh-Taylor不稳定性（RTI）在液膜破裂和一次雾化中的主导作用。至于在航空中的应用，液-气混合通常发生在高密度比和高雷诺数的挑战性条件下。因此，在这样的挑战性条件下对KHI和RTI的评估对更好地理解液体层的去稳定机理具有重要意义。为此，本研究重建了基于保守Allen-Cahn方程的格子Boltzmann多松弛时间（MRT）两相模型。最初，在大密度比和高雷诺数下，通过拉普拉斯定律测试了此MRT模型的数值稳定性和准确性，包括对流动性值的敏感性研究。之后，在雷诺数，密度比和粘度比的广泛范围内研究了KHI和RTI。数值结果表明，随着粘度比的增加，轻质流体的粘滞力增强，可显着抑制KHI和RTI中重质流体的卷起。至于密度比，它通常对KHI中的流体混合和RTI中的尖峰螺旋显示负面影响。但是，当密度比和雷诺数都达到较高水平时，由重流体主导的惯性力引起的开尔文-亥姆霍兹小波将引发严重的界面崩解。以上结果再次证明了本模型在应对挑战性条件方面的出色能力。除了，