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Composition of resolvents enhanced by random sweeping for large-scale structures in turbulent channel flows
Published online by Cambridge University Press: 07 February 2023
Abstract
Composite sweeping-enhanced resolvents, referred to as the ${\boldsymbol {R}}_s^2$ model, are proposed to predict the space–time statistics of large-scale structures in turbulent channel flows. This model incorporates two key mechanisms: (i) eddy damping is introduced to represent random sweeping decorrelation caused by nonlinear forcing, leading to a sweeping-enhanced resolvent
${{\boldsymbol {R}}_s}$; and (ii) the sweeping-enhanced resolvent
${{\boldsymbol {R}}_s}$ is composited into its iterations
${\boldsymbol {R}}_s^2$ to yield non-zero Taylor time microscales. The resulting
${\boldsymbol {R}}_s^2$ model can correctly predict the frequency spectra and two-point cross-spectra of large-scale structures. This model is compared numerically with eddy-viscosity-enhanced resolvent models. The latter are designed to represent energy transfer instead for time decorrelation, and thus underpredict the characteristic decay time scales. The
${\boldsymbol {R}}_s^2$ model correctly yields the characteristic decay time scales in turbulent channel flows.
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- © The Author(s), 2023. Published by Cambridge University Press
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