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Structure of high and low shear-stress events in a turbulent boundary layer

Structure of high and low shear-stress events in a turbulent boundary layer
Structure of high and low shear-stress events in a turbulent boundary layer
Simultaneous particle image velocimetry (PIV) and wall-shear-stress sensor measurements were performed to study structures associated with shear stress events in a flat plate turbulent boundary layer blackat a Reynolds number Re_\tau \approx 4000}. The PIV field-of-view covers 8\delta (where \delta is the boundary layer thickness) along the streamwise direction and captures the entire boundary layer in the wall-normal direction. Simultaneously, wall-shear-stress measurements were taken using a spanwise array of skin-friction sensors (spanning 2\delta). Based on this combination of measurements, the organization of the conditional wall-normal and streamwise velocity fluctuations (u and v) and of the Reynolds shear stress (-uv) can be extracted. Conditional averages of the velocity field are computed by dividing the histogram of the wall-shear-stress fluctuations into four quartiles, each containing 25\% of the occurrences. The conditional events corresponding to the extreme quartiles of the histogram (positive and negative) predominantly contribute to a change of velocity profile associated with the large structures and in the modulation of the small-scales. A detailed examination of the Reynolds shear stress contribution related to each of the four quartiles shows that the flow above a low wall-shear-stress event carries a larger amount of Reynolds shear stress than the other quartiles. The contribution of the small- and large-scales to this observation is discussed based on a scale decomposition of the velocity field.
2469-990X
1 - 19
Gomit, Guillaume
81e53723-d65a-46f5-bfc5-4ada63f6c5a9
De Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Gomit, Guillaume
81e53723-d65a-46f5-bfc5-4ada63f6c5a9
De Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052

Gomit, Guillaume, De Kat, Roeland and Ganapathisubramani, Bharathram (2018) Structure of high and low shear-stress events in a turbulent boundary layer Physical Review Fluids, 3, (1), 1 - 19. (doi:10.1103/PhysRevFluids.3.014609).

Record type: Article

Abstract

Simultaneous particle image velocimetry (PIV) and wall-shear-stress sensor measurements were performed to study structures associated with shear stress events in a flat plate turbulent boundary layer blackat a Reynolds number Re_\tau \approx 4000}. The PIV field-of-view covers 8\delta (where \delta is the boundary layer thickness) along the streamwise direction and captures the entire boundary layer in the wall-normal direction. Simultaneously, wall-shear-stress measurements were taken using a spanwise array of skin-friction sensors (spanning 2\delta). Based on this combination of measurements, the organization of the conditional wall-normal and streamwise velocity fluctuations (u and v) and of the Reynolds shear stress (-uv) can be extracted. Conditional averages of the velocity field are computed by dividing the histogram of the wall-shear-stress fluctuations into four quartiles, each containing 25\% of the occurrences. The conditional events corresponding to the extreme quartiles of the histogram (positive and negative) predominantly contribute to a change of velocity profile associated with the large structures and in the modulation of the small-scales. A detailed examination of the Reynolds shear stress contribution related to each of the four quartiles shows that the flow above a low wall-shear-stress event carries a larger amount of Reynolds shear stress than the other quartiles. The contribution of the small- and large-scales to this observation is discussed based on a scale decomposition of the velocity field.

Text FF10015-1 - Accepted Manuscript
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More information

Accepted/In Press date: 5 January 2018
e-pub ahead of print date: 19 January 2018
Published date: January 2018

Identifiers

Local EPrints ID: 417173
URI: https://eprints.soton.ac.uk/id/eprint/417173
ISSN: 2469-990X
PURE UUID: 73acc8be-6e61-4aed-ac9b-a572ed1b4720
ORCID for Roeland De Kat: ORCID iD orcid.org/0000-0002-6851-4409
ORCID for Bharathram Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

Catalogue record

Date deposited: 23 Jan 2018 17:30
Last modified: 23 Jan 2018 17:30

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