Coherence of intense localized vorticity in decaying two‐dimensional Navier–Stokes turbulence
Coherence of intense localized vorticity in decaying two‐dimensional Navier–Stokes turbulence
复制标题
衰减二维纳维-斯托克斯湍流中强烈局域涡度的相干性
DOI：
10.1063/1.858273
复制
发表时间：
1992
影响因子：
4.6
通讯作者：
N. Mattor
中科院分区：
文献类型：
--
作者：
P. Terry;D. Newman;N. Mattor
研究了二维强局部涡旋和衰减纳维尔-斯托克斯湍流的耦合演化，以识别和描述允许强涡旋区域与涡旋级联解耦并作为相干结构生存的物理过程。结果表明，湍流涡旋的剪切应变是由强涡的微分旋转引起的，从而产生了涡旋相干。用量纲分析和大剪切渐近极限封闭表示的解析解来确定由湍流应变产生的非均匀涡扩散率和涡中湍流的空间结构。当剪切应变率超过环境湍流应变率的适当测量值时，涡流内部的湍流波动局限于涡流边缘的窄层。同样地，涡旋扩散变弱，涡旋寿命变大，并且大大超过环境湍流的涡旋寿命。
The coupled evolution of an intense localized vortex and decaying Navier–Stokes turbulence in two dimensions is examined in order to identify and describe the physical process allowing regions of intense vorticity to decouple from the eddy cascade and survive as coherent structures. It is found that the shear straining of turbulent eddies by the differential rotation of the intense vortex gives rise to vortex coherence. Dimensional analysis and analytic solution of a closure representation in the asymptotic limit of large shear are used to determine a nonuniform vortex diffusivity produced by turbulent straining, and the spatial structure of turbulence in the vortex. When the shear straining rate exceeds the appropriate measure of the ambient turbulent straining rate, turbulent fluctuations in the vortex interior localize to a narrow layer in the vortex edge. Likewise, vortex diffusion becomes weak, the vortex lifetime becomes large, and greatly exceeds the eddy lifetimes of ambient turbulence.