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Law-of-the-wall for small-scale streamwise turbulence intensity in high-Reynolds-number turbulent boundary layers

Law-of-the-wall for small-scale streamwise turbulence intensity in high-Reynolds-number turbulent boundary layers
Law-of-the-wall for small-scale streamwise turbulence intensity in high-Reynolds-number turbulent boundary layers
Following the dimensional analysis approach carried out in previous studies, it is hypothesized that the small-scale fluctuations should only depend on the inner scales, analogous to the Prandtl's law-of-the-wall for the mean flow. This allows us to examine the high frequency regime of the streamwise energy spectra where a "law-of-the-wall" in spectra would hold. Observations in high-
Reynolds-number turbulent boundary layer data indicate that a conservative estimate for the start of this law-of-the-wall is f+ = 0.005 (which corresponds to 200 viscous time-units) across a range of wall-normal positions and Reynolds numbers. This is sufficient to capture the energetic viscous-scaled motions such as the near-wall streaks, which has a time scale of approximately 100 viscous
units. This spectral collapse is consistent with the observations in internal
flows and external flows in other studies. Furthermore, the spectral collapse leads to a universal scaling (based on skin-friction velocity and kinematic viscosity) for the small-scale streamwise turbulence variance (consistent with the hypothesis) across the entire boundary layer. A logarithmic variation of this
small-scale variance is observed farther away from the wall.
2469-990X
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052

Ganapathisubramani, Bharathram (2018) Law-of-the-wall for small-scale streamwise turbulence intensity in high-Reynolds-number turbulent boundary layers. Physical Review Fluids, 3, [104607]. (doi:10.1103/PhysRevFluids.3.104607).

Record type: Article

Abstract

Following the dimensional analysis approach carried out in previous studies, it is hypothesized that the small-scale fluctuations should only depend on the inner scales, analogous to the Prandtl's law-of-the-wall for the mean flow. This allows us to examine the high frequency regime of the streamwise energy spectra where a "law-of-the-wall" in spectra would hold. Observations in high-
Reynolds-number turbulent boundary layer data indicate that a conservative estimate for the start of this law-of-the-wall is f+ = 0.005 (which corresponds to 200 viscous time-units) across a range of wall-normal positions and Reynolds numbers. This is sufficient to capture the energetic viscous-scaled motions such as the near-wall streaks, which has a time scale of approximately 100 viscous
units. This spectral collapse is consistent with the observations in internal
flows and external flows in other studies. Furthermore, the spectral collapse leads to a universal scaling (based on skin-friction velocity and kinematic viscosity) for the small-scale streamwise turbulence variance (consistent with the hypothesis) across the entire boundary layer. A logarithmic variation of this
small-scale variance is observed farther away from the wall.

Text
Law-of-the-wall for small-scale streamwise turbulence intensity in high-Reynolds-number - Accepted Manuscript
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Accepted/In Press date: 13 October 2018
e-pub ahead of print date: 31 October 2018

Identifiers

Local EPrints ID: 425751
URI: http://eprints.soton.ac.uk/id/eprint/425751
ISSN: 2469-990X
PURE UUID: a5403a78-ea34-4f8c-b8b0-38f65b754f4f
ORCID for Bharathram Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 02 Nov 2018 17:30
Last modified: 26 Nov 2021 02:56

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