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Simultaneous velocity and density measurements of fully developed Rayleigh-Taylor mixing
Physical Review Fluids ( IF 2.7 ) Pub Date : 2021-07-19 , DOI: 10.1103/physrevfluids.6.073902 Mark Mikhaeil , Prasoon Suchandra , Devesh Ranjan , Gokul Pathikonda
Physical Review Fluids ( IF 2.7 ) Pub Date : 2021-07-19 , DOI: 10.1103/physrevfluids.6.073902 Mark Mikhaeil , Prasoon Suchandra , Devesh Ranjan , Gokul Pathikonda
The dynamics of molecular mixing and the energy transfer process in the Rayleigh-Taylor instability (RTI) are studied through the collection of simultaneous density-velocity measurements. These experiments provide simultaneous density-velocity field measurements, in contrast to previous point measurements. Statistically stationary experiments are performed in a “convective-type” gas tunnel facility, with density contrast achieved through the injection of helium into the bottom stream. Three experiments at Atwood number are captured at three outer scale Reynolds numbers , and 4050. Particle image velocimetry and laser induced fluorescence are employed simultaneously. Statistics of the density and velocity show self-similar collapse of RTI profiles at large Reynolds number . Flat velocity profiles indicate homogeneous turbulence characteristics in the core of the mixing region. Significant anisotropy develops in the flow, with horizontal velocity fluctuations being only 60% of the vertical velocity fluctuations. The turbulent mass flux is found to be asymmetric about the centerline, with increased peak towards the spike. Measurements of the molecular mixing show that mixing is maximized at the core of the flow and increases with increased Reynolds number. The transport equation of density-specific-volume correlation shows that it is mostly produced in the core of the mixing region, and that the spatial evolution of its profile is the result of transport by bulk motion of the bubble and spike. Energy transfer from gravitational potential energy to turbulent kinetic energy and viscous dissipation is observed to occur in the experiment with a ratio of dissipated energy to potential energy released of 38%. The analysis of the turbulent kinetic energy transport equation budget reveals that production is the primary mechanism towards the growth of turbulent kinetic energy in the core of the flow, and is asymmetrically slightly skewed towards the spike. However, it is through the transport that the strong advection at the edges of the mixing region is maintained.
中文翻译:
完全发展的瑞利-泰勒混合的同时速度和密度测量
通过同时收集密度-速度测量值,研究了瑞利-泰勒不稳定性 (RTI) 中分子混合的动力学和能量转移过程。与以前的点测量相比,这些实验提供了同步的密度-速度场测量。统计平稳实验在“对流型”气体隧道设施中进行,通过向底部流中注入氦气来实现密度对比。阿特伍德数的三个实验 以三个外部尺度雷诺数捕获 , 和 4050。同时采用粒子图像测速和激光诱导荧光。密度和速度的统计数据显示了在大雷诺数下 RTI 剖面的自相似坍塌. 平坦的速度分布表明混合区域核心的均匀湍流特性。流动中产生了显着的各向异性,水平速度波动仅为垂直速度波动的 60%。发现湍流质量通量关于中心线不对称,峰值朝向尖峰增加。分子混合的测量表明混合在流动的核心处最大化并且随着雷诺数的增加而增加。密度-比体积相关的输运方程表明它主要产生于混合区的核心,其剖面的空间演化是气泡和尖峰整体运动传输的结果。实验中观察到能量从重力势能转移到湍动能和粘性耗散,耗散能与释放的势能之比为 38%。湍动能输运方程收支的分析表明,生产是流动核心湍动能增长的主要机制,并且不对称地略微偏向尖峰。然而,正是通过传输,混合区域边缘的强平流得以维持。
更新日期:2021-07-20
中文翻译:
完全发展的瑞利-泰勒混合的同时速度和密度测量
通过同时收集密度-速度测量值,研究了瑞利-泰勒不稳定性 (RTI) 中分子混合的动力学和能量转移过程。与以前的点测量相比,这些实验提供了同步的密度-速度场测量。统计平稳实验在“对流型”气体隧道设施中进行,通过向底部流中注入氦气来实现密度对比。阿特伍德数的三个实验 以三个外部尺度雷诺数捕获 , 和 4050。同时采用粒子图像测速和激光诱导荧光。密度和速度的统计数据显示了在大雷诺数下 RTI 剖面的自相似坍塌. 平坦的速度分布表明混合区域核心的均匀湍流特性。流动中产生了显着的各向异性,水平速度波动仅为垂直速度波动的 60%。发现湍流质量通量关于中心线不对称,峰值朝向尖峰增加。分子混合的测量表明混合在流动的核心处最大化并且随着雷诺数的增加而增加。密度-比体积相关的输运方程表明它主要产生于混合区的核心,其剖面的空间演化是气泡和尖峰整体运动传输的结果。实验中观察到能量从重力势能转移到湍动能和粘性耗散,耗散能与释放的势能之比为 38%。湍动能输运方程收支的分析表明,生产是流动核心湍动能增长的主要机制,并且不对称地略微偏向尖峰。然而,正是通过传输,混合区域边缘的强平流得以维持。