Direct numerical simulations of temporal compressible mixing layers in a Bethe–Zel'dovich–Thompson dense gas: influence of the convective Mach number
Direct numerical simulations of temporal compressible mixing layers in a Bethe–Zel'dovich–Thompson dense gas: influence of the convective Mach number
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DOI：
10.1017/jfm.2021.511
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发表时间：
2021-07
影响因子：
3.7
通讯作者：
A. Vadrot;A. Giauque;C. Corre
中科院分区：
文献类型：
--
作者：
A. Vadrot;A. Giauque;C. Corre
摘要本文研究了BZT（Bethe-Zel'dovich-Thompson）稠密气体（FC-70）在三种不同对流马赫数$M_c=0.1$、1.1和2.2下对湍流可压缩混合层发展的影响。本研究扩展了以前在M_c=1.1$时进行的分析（Vadrot等人，流体力学杂志，vol. 893，2020）用FC-70和空气分别采用五阶Martin-Hou热力学状态方程（EoS）和理想气体EoS对可压缩混合层进行了三维直接数值模拟（DNS）。经过仔细定义的自相似周期使用的时间演变的综合流向生产项，混合层的增长率作为对流马赫数的函数的演变进行比较之间的完美的气体和致密的气体流动。结果表明，在M_c=2.2时，动量厚度增长率有较大差别.众所周知的压缩性相关的动量厚度增长率的减少是减少在致密气体。波动的热力学量被强烈地修正。特别是，温度变化被抑制，导致几乎等温演变。小尺度动力学也受到稠密气体效应的影响，这要求在使用大涡模拟计算稠密气体流动时使用特定的亚网格尺度模型。在其他三个初始热力学操作点进行额外的稠密气体DNS。在BZT反型区外部和内部进行的DNS没有显示出重大差异。因此，BZT效应本身对混合层生长的影响很小。
Abstract The present article investigates the effects of a BZT (Bethe–Zel'dovich–Thompson) dense gas (FC-70) on the development of turbulent compressible mixing layers at three different convective Mach numbers $M_c=0.1$, 1.1 and 2.2. This study extends a previous analysis conducted at $M_c=1.1$ (Vadrot et al., J. Fluid Mech., vol. 893, 2020) Several three-dimensional direct numerical simulations (DNS) of compressible mixing layers are performed with FC-70 using the fifth-order Martin–Hou thermodynamic equation of state (EoS) and air using the perfect gas EoS. After having carefully defined self-similar periods using the temporal evolution of the integrated streamwise production term, the evolutions of the mixing layer growth rate as a function of the convective Mach number are compared between perfect gas and dense gas flows. Results show major differences for the momentum thickness growth rate at $M_c=2.2$. The well-known compressibility-related decrease of the momentum thickness growth rate is reduced in the dense gas. Fluctuating thermodynamics quantities are strongly modified. In particular, temperature variations are suppressed, leading to an almost isothermal evolution. The small scales dynamics is also influenced by dense gas effects, which calls for a specific sub-grid-scale model when computing dense gas flows using large eddy simulation. Additional dense gas DNS are performed at three other initial thermodynamic operating points. DNS performed outside and inside the BZT inversion region do not show major differences. BZT effects themselves therefore only have a small impact on the mixing layer growth.