Data-driven decomposition of the streamwise turbulence kinetic energy in boundary layers. Part 1. Energy spectra

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  • Woutijn J. Baars
  • ,
  • Ivan Marusic, University of Melbourne

In wall-bounded turbulence, a multitude of coexisting turbulence structures form the streamwise velocity energy spectrum from the viscosity-to the inertia-dominated range of scales. Definite scaling-trends for streamwise spectra have remained empirically elusive, although a prominent school of thought stems from the works of Perry & Abell (J. Fluid Mech., vol. 79, 1977, pp. 785-799) and Perry et al. (J. Fluid Mech., vol. 165, 1986, pp. 163-199), which were greatly inspired by the attached-eddy hypothesis of Townsend (The Structure of Turbulent Shear Flow, Cambridge University Press, 1976). In this paper, we re-examine the turbulence kinetic energy of the streamwise velocity component in the context of the spectral decompositions of Perry and co-workers. Two universal spectral filters are derived via spectral coherence analysis of two-point velocity signals, spanning a Reynolds-number range to and form the basis for our decomposition of the logarithmic-region turbulence into stochastically wall-detached and wall-attached portions of energy. The latter is composed of scales larger than a streamwise/wall-normal ratio of. If the decomposition is accepted, a scaling region can only appear for, at a wall-normal position of. Following Perry and co-workers, it is hypothesized that spectral contributions from turbulence structures other than attached eddies obscure a scaling. When accepting the idea of different spectral contributions it is furthermore shown that a broad outer-spectral peak is present even at low.

TidsskriftJournal of Fluid Mechanics
Sider (fra-til)A251-A2540
StatusUdgivet - jan. 2020

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