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Evolution of turbulence and in-plane vortices in the near field flow behind multi-scale planar grids.

Gan, L. and Krogstad, P.-Å. (2016) 'Evolution of turbulence and in-plane vortices in the near field flow behind multi-scale planar grids.', Physics of fluids., 28 (8). 085101.

Abstract

In this experimental work, we carry out detailed two-dimensional particle image velocimetry investigations for the near field wakes behind a conventional and two multi-scale planar grids, using stitched camera fields of view. Statistical independent measurements are conducted focusing on the first few mesh distances downstream of the grid. It is found that the multiple integral length scales originated from the grids loose their importance on the turbulence development after about three mesh distances downstream, much earlier than the distance where the turbulence becomes homogeneous. The largest eddy size, represented by the integral length scales, does not show clear differences in its growth rate among the three grids after an initial development of three times the largest grid size downstream. Nevertheless, when examining individual vortex behaviours using conditional averaging and filtering processes, clear differences are found. The grids are found to have different decay rates of peak vorticity and projected vortex strengths. Despite these differences, the in-plane vorticity correlation function reveals that the mean vortex shape of all the grids shows a universal near-Gaussian pattern which does not change much as the turbulence decays.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1063/1.4960025
Publisher statement:© 2016 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Gan, L. & Krogstad, P.-Å. (2016). Evolution of turbulence and in-plane vortices in the near field flow behind multi-scale planar grids. Physics of Fluids 28(8): 085101 and may be found at https://doi.org/10.1063/1.4960025
Date accepted:18 July 2016
Date deposited:06 October 2016
Date of first online publication:08 August 2016
Date first made open access:08 August 2017

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