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Spatial-spectral characteristics of momentum transport in a turbulent boundary layer

Spatial-spectral characteristics of momentum transport in a turbulent boundary layer
Spatial-spectral characteristics of momentum transport in a turbulent boundary layer
wall, longer time and larger length scales exhibit an increasing spectral content. Wave velocities of transport events are estimated from wavenumber–frequency power spectra at different wall-normal locations. Wave velocities associated with Spectral content and spatial organization of momentum transport events are investigated in a turbulent boundary layer at the Reynolds number (Re ) = 2700, with time-resolved planar particle image velocimetry. The spectral content of the Reynolds-shear-stress fluctuations reveals that the largest range of time and length scales can be observed in proximity to the wall, while this range becomes progressively more narrow when the wall distance increases. Farther from the ejection events (Q2) are lower than the local average streamwise velocity, while sweep events (Q4) are characterized by wave velocities larger than the local average velocity. These velocity deficits are almost insensitive to the wall distance, which is also confirmed from time tracking the intense transport events. The vertical advection velocities of the intense ejection and sweep events are on average a small fraction of the friction velocity U , different from previous observations in a channel flow. In the range of wall-normal locations 60 < y+ < 600, sweeps are considerably larger than ejections, which could be because the ejections are preferentially located in between the legs of hairpin packets. Finally, it is observed that negative quadrant events of the same type tend to appear in groups over a large spatial streamwise extent.
0022-1120
599-634
Fiscaletti, Daniele
b60d3ad4-c0c7-4990-b141-ecec8f90b4c9
De Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Fiscaletti, Daniele
b60d3ad4-c0c7-4990-b141-ecec8f90b4c9
De Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052

Fiscaletti, Daniele, De Kat, Roeland and Ganapathisubramani, Bharathram (2018) Spatial-spectral characteristics of momentum transport in a turbulent boundary layer. Journal of Fluid Mechanics, 599-634. (doi:10.1017/jfm.2017.841).

Record type: Article

Abstract

wall, longer time and larger length scales exhibit an increasing spectral content. Wave velocities of transport events are estimated from wavenumber–frequency power spectra at different wall-normal locations. Wave velocities associated with Spectral content and spatial organization of momentum transport events are investigated in a turbulent boundary layer at the Reynolds number (Re ) = 2700, with time-resolved planar particle image velocimetry. The spectral content of the Reynolds-shear-stress fluctuations reveals that the largest range of time and length scales can be observed in proximity to the wall, while this range becomes progressively more narrow when the wall distance increases. Farther from the ejection events (Q2) are lower than the local average streamwise velocity, while sweep events (Q4) are characterized by wave velocities larger than the local average velocity. These velocity deficits are almost insensitive to the wall distance, which is also confirmed from time tracking the intense transport events. The vertical advection velocities of the intense ejection and sweep events are on average a small fraction of the friction velocity U , different from previous observations in a channel flow. In the range of wall-normal locations 60 < y+ < 600, sweeps are considerably larger than ejections, which could be because the ejections are preferentially located in between the legs of hairpin packets. Finally, it is observed that negative quadrant events of the same type tend to appear in groups over a large spatial streamwise extent.

Text Spatial_spectral_characteristics_of_momentum - Accepted Manuscript
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Accepted/In Press date: 1 December 2017
e-pub ahead of print date: 12 December 2017
Published date: 10 February 2018

Identifiers

Local EPrints ID: 416171
URI: https://eprints.soton.ac.uk/id/eprint/416171
ISSN: 0022-1120
PURE UUID: 04ff6f80-f1d3-4f52-bb29-615cacf5c1d3
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: 06 Dec 2017 17:30
Last modified: 23 May 2018 16:32

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