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Media type:
E-Article
Title:
On the relevance of Reynolds stresses in resolvent analyses of turbulent wall-bounded flows
Contributor:
Morra, Pierluigi;
Semeraro, Onofrio;
Henningson, Dan S.;
Cossu, Carlo
Published:
Cambridge University Press (CUP), 2019
Published in:
Journal of Fluid Mechanics, 867 (2019), Seite 969-984
Language:
English
DOI:
10.1017/jfm.2019.196
ISSN:
0022-1120;
1469-7645
Origination:
Footnote:
Description:
The ability of linear stochastic response analysis to estimate coherent motions is investigated in turbulent channel flow at the friction Reynolds number $\text{Re}_{\unicode[STIX]{x1D70F}}=1007$. The analysis is performed for spatial scales characteristic of buffer-layer and large-scale motions by separating the contributions of different temporal frequencies. Good agreement between the measured spatio-temporal power spectral densities and those estimated by means of the resolvent is found when the effect of turbulent Reynolds stresses, modelled with an eddy-viscosity associated with the turbulent mean flow, is included in the resolvent operator. The agreement is further improved when the flat forcing power spectrum (white noise) is replaced with a power spectrum matching the measures. Such a good agreement is not observed when the eddy-viscosity terms are not included in the resolvent operator. In this case, the estimation based on the resolvent is unable to select the right peak frequency and wall-normal location of buffer-layer motions. Similar results are found when comparing truncated expansions of measured streamwise velocity power spectral densities based on a spectral proper orthogonal decomposition to those obtained with optimal resolvent modes.