How does turbulence mix a stratified fluid?
How does turbulence mix a stratified fluid?
复制标题
湍流如何混合分层流体？
DOI：
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发表时间：
2022
影响因子：
3.7
通讯作者：
J. Riley
中科院分区：
文献类型：
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作者：
J. Riley
稳定分层流中的一个重要课题是湍流如何不可逆地混合周围的密度场。由于密度场通过稳定分层动态地耦合到速度场，因此这种混合影响整体流动动力学，并且其精确参数化已经成为环境流体力学中的“巨大挑战”（Dauxois等人，Fluids，第6卷，第2期，2021，020501）。为了更好地理解稳定分层流体中混合的详细运动学，Jiang等人（2022）使用独特的实验室设施进行实验，该实验室设施能够产生可控的分层剪切流，并在高分辨率三维网格上提供几乎瞬时的密度和三分量速度测量。使用来自实验的三维数据集，他们采用旋转剪切分解来识别流场中瞬时旋转的形态，从而解释旋转的运动，并最终解释旋转如何导致密度场的不可逆混合。这标志着在实验室环境中充分利用高分辨率三维近瞬时测量的首批研究之一;它展示了在实验室中可以完成的工作，为未来的实验设定了新的标准。
Abstract A principal topic of interest and importance in stably stratified flows is how turbulence irreversibly mixes the ambient density field. Because the density field is coupled dynamically to the velocity field through the stable stratification, this mixing affects the overall flow dynamics, and its accurate parameterisation has become a ‘grand challenge’ in environmental fluid mechanics (Dauxois et al., Phys. Rev. Fluids, vol. 6, issue 2, 2021, 020501). In order to better understand the detailed kinematics of mixing in a stably stratified fluid, Jiang et al. (2022) perform experiments using a unique laboratory facility, capable of generating controllable stratified shear flows, and providing almost instantaneous density and three-component velocity measurements on a high-resolution, three-dimensional grid. Using three-dimensional data sets from the experiments, they employ the rortex–shear decomposition to identify the morphology of instantaneous rortices in the flow fields, leading to the interpretation of the motion of the rortices and ultimately to how the rortices cause irreversible mixing of the density field. This marks one of the first studies where, in a laboratory setting, full use has been made of somewhat high-resolution, three-dimensional near-instantaneous measurements; it demonstrates what can be accomplished in the laboratory, setting a new standard for future experiments.