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Velocity–vorticity correlation structure in turbulent channel flow

Published online by Cambridge University Press:  24 February 2014

Jun Chen
Affiliation:
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
Fazle Hussain
Affiliation:
Texas Tech University, Department of Mechanical Engineering, Box 41021, Lubbock, TX 79409-1021, USA
Jie Pei
Affiliation:
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
Zhen-Su She*
Affiliation:
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
*
†Email address for correspondence: she@pku.edu.cn
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Abstract

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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 $|R_{ij} (y_r; x, y, z)|\geqslant R_0$ to define a topologically invariant high-correlation region, called $\mathit{VVCS}_{ij}$ . The method is applied to direct numerical simulation (DNS) data, and it is shown that the $\mathit{VVCS}_{ij}$ 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 VVCS is that its geometry continuously varies with $y_r$ . A topological change of $\mathit{VVCS}_{11}$ 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.

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Type
Papers
Creative Commons
Creative Common License - CCCreative Common License - BY
The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution licence .
Copyright
© 2014 Cambridge University Press

Chen et al. supplementary movie

The shape change of VVCS11 with yr.

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