Transition stages of Rayleigh-Taylor instability between miscible fluids
Transition stages of Rayleigh-Taylor instability between miscible fluids
复制标题
DOI：
10.1017/s0022112001005377
复制
发表时间：
2001-09-25
影响因子：
3.7
通讯作者：
Dimotakis, PE
中科院分区：
文献类型：
--
作者：
Cook, AW;Dimotakis, PE
直接数值模拟 (DNS) 展示了密度比为 3:1 的两种不可压缩、可混溶流体之间的三维瑞利-泰勒不稳定性 (RTI)。在矩形域的水平方向上施加周期性边界条件，具有无滑移的顶壁和底壁。获得了纳维-斯托克斯方程的解，并通过具有各种初始扰动的物质传输扩散方程进行了增强。根据混合区高度及其增长率，DNS 实现了超过 3000 的外尺度雷诺数。初始增长是扩散的，并且与初始扰动无关。现有的线性稳定性理论无法预测非线性增长的开始。在扩散增长阶段之后，发现增长率取决于最初的扰动，直到模拟结束。研究发现，混合对初始条件的影响比对增长率的影响更为敏感。泰勒微尺度和雷诺数在整个模拟过程中是各向异性的。如果使用混合区的高度而不是时间作为缩放或进度变量，则可以改善许多统计数据的崩溃。混合对该流动具有动力学影响，因为它是由施加的加速度场对局部密度差的作用驱动的。
Direct numerical simulations (DNS) are presented of three-dimensional, Rayleigh-Taylor instability (RTI) between two incompressible, miscible fluids, with a 3:1 density ratio. Periodic boundary conditions are imposed in the horizontal directions of a rectangular domain, with no-slip top and bottom walls. Solutions are obtained for the Navier-Stokes equations, augmented by a species transport-diffusion equation, with various initial perturbations. The DNS achieved outer-scale Reynolds numbers, based on mixing-zone height and its rate of growth, in excess of 3000. Initial growth is diffusive and independent of the initial perturbations. The onset of nonlinear growth is not predicted by available linear-stability theory. Following the diffusive-growth stage, growth rates are found to depend on the initial perturbations, up to the end of the simulations. Mixing is found to be even more sensitive to initial conditions than growth rates. Taylor microscales and Reynolds numbers are anisotropic throughout the simulations. Improved collapse of many statistics is achieved if the height of the mixing zone, rather than time, is used as the scaling or progress variable. Mixing has dynamical consequences for this flow, since it is driven by the action of the imposed acceleration field on local density differences.