Large-scale characteristics of stratified wake turbulence at varying Reynolds number
Large-scale characteristics of stratified wake turbulence at varying Reynolds number
复制标题
不同雷诺数下层状尾流湍流的大尺度特征
DOI：
10.1103/physrevfluids.4.084802
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发表时间：
2019
影响因子：
2.7
通讯作者：
P. Diamessis
中科院分区：
文献类型：
--
作者：
Qi Zhou;P. Diamessis
我们分析了具有浮力频率和运动粘度的均匀分层Boussinesq流体中直径速度的拖曳球尾迹的大涡模拟数据集。使用基于谱多域惩罚方法的不可压缩Navier-Stokes解算器模拟这些时间演变的尾迹，从而能够系统地检查三个不同值的分层尾迹。因此，本文特别关注了变分对分层尾流大尺度特征演化的影响。我们研究了水平和垂直积分长度尺度（和），水平和垂直波动速度（和），局部垂直剪切的演变，以及基于上述量的无量纲参数。特别是，垂直湍流弗劳德数被发现是有序统一的，这是在各向异性流层之间发生剪切不稳定的强分层状态下的动力学特征。水平湍流雷诺数随时间保持近似常数，水平湍流弗劳德数随时间衰减为，与自由衰减湍流的标度分析一致。我们描述了不同分层流型之间的转换，并研究了基于体的参数对这些转换的影响。从弱分层制度到强分层制度的转变，其标志是衰变为统一，发生在。我们进一步表明，流动完成上述过渡尺度的初始值为，这提供了一种方法来预测给定和尾迹进入强分层状态的可能性。本文所报道的分析是试图用雷诺数来获得分层尾迹湍流的预测能力，将强分层湍流理论（迄今为止通常用于均匀湍流）的选定元素应用于典型的非均匀湍流自由剪切流。
We analyze a large-eddy simulation data set of wakes of a towed sphere of diameterat speedin a uniformly stratified Boussinesq fluid with buoyancy frequencyand kinematic viscosity. These temporally evolving wakes are simulated using a spectral multidomain penalty-method-based incompressible Navier-Stokes solver forand, enabling a systematic examination of stratified wakes at three different values ofsufficiently separated in magnitude. As such, particular attention is paid to the effects of varyingon the evolution of large-scale characteristics of stratified wake turbulence. We examine the evolution of horizontal and vertical integral length scales (and), horizontal and vertical fluctuation velocities (and), local vertical shear, as well as the resulting dimensionless parameters based on the above quantities. In particular, the vertical turbulent Froude numberis found to be of order unity, a signature of the dynamics in the strongly stratified regime where shear instabilities develop between anisotropic flow layers. The horizontal turbulent Reynolds numberstays approximately constant in time and the horizontal turbulent Froude numberdecays in time as, consistent with scaling analysis of freely decaying turbulence. We characterize the transitions between distinct stratified flow regimes and examine the effects of body-based parametersandon these transitions. The transition from the weakly to the strongly stratified regime, which is marked bydecaying to unity, occurs when. We further show that the initial value ofat which the flow completes the above transition scales as, which provides a way to predict the possibility of accessing the strongly stratified regime for a wake of givenand. The analysis reported here constitutes an attempt to obtain the predictive capability of stratified wake turbulence in terms of Reynolds number, applying select elements of strongly stratified turbulence theory, so far typically utilized for homogeneous turbulence, to a canonical inhomogeneous turbulent free-shear flow.
水平强制分层湍流中的层形成：将精确的相干结构与线性不稳定性联系起来
影响因子：
3.7
作者：
Lucas D
通讯作者：
Lucas D