Velocity-vorticity correlation structure in turbulent channel flow
Velocity-vorticity correlation structure in turbulent channel flow
复制标题
湍流河道流中的速度-涡度相关结构
DOI：
10.1017/jfm.2014.3
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发表时间：
2014-03-01
影响因子：
3.7
通讯作者：
She, Zhen-Su
中科院分区：
文献类型：
--
作者：
Chen, Jun;Hussain, Fazle;She, Zhen-Su
利用速度和涡度分量的两点互相关系数R-ij，u(I)和omega(J)，(i，j=1，2，3)，提出了一种新的统计相干结构--速度涡度相关结构(VVCS)，作为描述速度涡度相关结构的有用参数。对于具有壁法向y的湍流槽道流动，VVCS研究包括在固定参考位置y(R)使用u(I)，并使用竖条R-ij(Y-r；x，y，z)竖条R-0来定义一个拓扑不变的高相关区域，称为VVCSu。将该方法应用于直接数值模拟数据，结果表明，VVCSij定性和定量地捕捉了近壁CS的所有已知几何特征，包括准流向涡和条纹的展向间距、流向长度和倾角。VVCS11的一个显著特征是其几何形状随y(R)连续变化。在y(R)(+)=110时，VVCSii从四极(对于较小的y(R))到偶极(对于较大的y(R))发生了拓扑变化，从几何上解释了壁面边界湍流剪切流的多层性质。总之，VVCS提供了一种新的稳健的方法来量化壁面有界流动中的CS，特别适合于利用热线、粒子图像测速/激光多普勒风速测量或DNS/大涡模拟数据中的两点同步数据来提取统计几何度量。
A new statistical coherent structure (CS), the velocity vorticity correlation structure (VVCS), using the two-point cross-correlation coefficient R-ij of velocity and vorticity components, u(i) and omega(j), (i, j = 1, 2, 3), is proposed as a useful descriptor of CS. For turbulent channel flow with the wall-normal direction y, a VVCS study consists of using u(i) at a fixed reference location y(r), and using vertical bar R-ij(Y-r; x, y, z)vertical bar R-0 to define a topologically invariant high-correlation region, called VVCSu. The method is applied to direct numerical simulation (DNS) data, and it is shown that the VVCSij qualitatively and quantitatively captures all known geometrical features of near-wall CS, including spanwise spacing, streamwise length and inclination angle of the quasi-streamwise vortices and streaks. A distinct feature of the VVCS11 is that its geometry continuously varies with y(r). A topological change of VVCSii from quadrupole (for smaller y(r)) to dipole (for larger y(r)) occurs at y(r)(+) = 110, giving a geometrical interpretation of the multilayer nature of wall-bounded turbulent shear flows. In conclusion, the VVCS provides a new robust method to quantify CS in wall-bounded flows, and is particularly suitable for extracting statistical geometrical measures using two-point simultaneous data from hotwire, particle image velocimetry/laser Doppler anemometry measurements or DNS/large eddy simulation data.