On the validity of the quasi-steady-turbulence hypothesis in representing the effects of large scales on small scales in boundary layers
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Published version
Author(s)
Agostini, L
Leschziner, M
Type
Journal Article
Abstract
The “quasi-steady hypothesis,” as understood in the context of large-scale/small-scale interactions in near-wall turbulence, rests on the assumption that the small scales near the wall react within very short time scales to changes imposed on them by energetic large scales whose length scales differ by at least one order of magnitude and whose energy reaches a maximum in the middle to the outer portion of the log-law layer. A key statistical manifestation of this assumption is that scaling the small-scale motions with the large-scale wall-friction-velocity footprints renders the small-scale statistics universal. This hypothesis is examined here by reference to direct numerical simulation (DNS) data for channel flow at Reτ ≈ 4200, subjected to a large-scale/small-scale separation by the empirical mode decomposition method. Flowproperties examined include the mean velocity, second moments, joint probability density functions, and skewness. It is shown that the validity of the hypothesis depends on the particular property being considered and on the range of length scales of structures included within the large-scale spectrum. The quasi-steady hypothesis is found to be well justified for the mean velocity and streamwise energy of the small scales up to y+∼O(80)y+∼O(80), but only up to y+∼O(30)y+∼O(30) for other properties.
Date Issued
2016-04-01
Date Acceptance
2016-03-11
Citation
Physics of Fluids, 2016, 28 (4)
ISSN
1089-7666
Publisher
American Institute of Physics
Journal / Book Title
Physics of Fluids
Volume
28
Issue
4
Copyright Statement
© 2016 AIP Publishing LLC. 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 Physics of Fluids and may be found at http://dx.doi.org/10.1063/1.4944735
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Grant Number
EP/G061556/1
Subjects
Fluids & Plasmas
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Publication Status
Published
Article Number
045102