Turbulence spectra in smooth- and rough-wall pipe flow at extreme Reynolds numbers

B. J. Rosenberg, M. Hultmark, M. Vallikivi, S. C.C. Bailey, A. J. Smits

Research output: Contribution to journalArticle

61 Scopus citations

Abstract

Well-resolved streamwise velocity spectra are reported for smooth- and rough-wall turbulent pipe flow over a large range of Reynolds numbers. The turbulence structure far from the wall is seen to be unaffected by the roughness, in accordance with Townsend's Reynolds number similarity hypothesis. Moreover, the energy spectra within the turbulent wall region follow the classical inner and outer scaling behaviour. While an overlap region between the two scalings and the associated kx-1 law are observed near R+~ 3000, the kx-1 behaviour is obfuscated at higher Reynolds numbers due to the evolving energy content of the large scales (the very-large-scale motions, or VLSMs). We apply a semi-empirical correction (del Álamo & Jiménez, J. Fluid Mech., vol. 640, 2009, pp. 5-26) to the experimental data to estimate how Taylor's frozen field hypothesis distorts the pseudo-spatial spectra inferred from time-resolved measurements. While the correction tends to suppress the long wavelength peak in the logarithmic layer spectrum, the peak nonetheless appears to be a robust feature of pipe flow at high Reynolds number. The inertial subrange develops around R+ > 2000 where the characteristic kx 5/3 region is evident, which, for high Reynolds numbers, persists in the wake and logarithmic regions. In the logarithmic region, the streamwise wavelength of the VLSM peak scales with distance from the wall, which is in contrast to boundary layers, where the superstructures have been shown to scale with boundary layer thickness throughout the entire shear layer. Moreover, the similarity in the streamwise wavelength scaling of the large- and very-large-scale motions supports the notion that the two are physically interdependent.

Original languageEnglish (US)
Pages (from-to)46-63
Number of pages18
JournalJournal of Fluid Mechanics
Volume731
DOIs
StatePublished - Sep 1 2013

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Keywords

  • Boundary layer structure
  • Turbulent boundary layers

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