On the relevance of Reynolds stresses in resolvent analyses of turbulent wall-bounded flows

Abstract : The ability of linear stochastic response analysis to estimate coherent motions is investigated in turbulent channel flow at friction Reynolds number Re τ = 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 to 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.
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Dernière modification le : mercredi 12 juin 2019 - 11:38:36

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Pierluigi Morra, Onofrio Semeraro, Dan Henningson, Carlo Cossu. On the relevance of Reynolds stresses in resolvent analyses of turbulent wall-bounded flows. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2019, 867, pp.969-984. ⟨10.1017/jfm.2019.196⟩. ⟨hal-02111454⟩

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