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The instantaneous structure of secondary flows in turbulent boundary layers

The instantaneous structure of secondary flows in turbulent boundary layers
The instantaneous structure of secondary flows in turbulent boundary layers
Secondary flows can develop in turbulent boundary layers that grow over surfaces with spanwise inhomogeneities. In this article, we demonstrate the formation of secondary flows in both experimental and numerical tests and dissect the instantaneous structure and topology of these secondary motions. We show that the formation of secondary flows is not very sensitive to the Reynolds number range investigated, and direct numerical simulations and experiments produce similar results in the mean flow as well as the dispersive and turbulent stress distributions. The numerical methods capture time-resolved features of the instantaneous flow and provide insight into the near-wall flow structures, that were previously obscured in the experimental measurements. Proper orthogonal decomposition was shown to capture the essence of the secondary flows in relatively few modes and to be useful as a filter to analyse the instantaneous flow patterns. The secondary flows are found to create extended regions of high Reynolds stress away from the wall that comprise predominantly sweeps similar to what one would expect to see near the wall and which are comparable in magnitude to the near-wall stress. Analysis of the instantaneous flow patterns reveals that the secondary flows are the result of a non-homogeneous distribution of mid-size vortices.
0022-1120
845-870
Vanderwel, C.
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Stroh, A.
5e6a12ec-abf0-46e9-a4c4-38d67fda1b62
Kriegseis, J.
51a6869b-08e1-4c17-ae73-db17d9d48f1d
Frohnapfel, B.
dc7e8b4e-540f-4a65-bc74-96c826fcd69e
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Vanderwel, C.
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Stroh, A.
5e6a12ec-abf0-46e9-a4c4-38d67fda1b62
Kriegseis, J.
51a6869b-08e1-4c17-ae73-db17d9d48f1d
Frohnapfel, B.
dc7e8b4e-540f-4a65-bc74-96c826fcd69e
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052

Vanderwel, C., Stroh, A., Kriegseis, J., Frohnapfel, B. and Ganapathisubramani, B. (2019) The instantaneous structure of secondary flows in turbulent boundary layers. Journal of Fluid Mechanics, 862, 845-870. (doi:10.1017/jfm.2018.955).

Record type: Article

Abstract

Secondary flows can develop in turbulent boundary layers that grow over surfaces with spanwise inhomogeneities. In this article, we demonstrate the formation of secondary flows in both experimental and numerical tests and dissect the instantaneous structure and topology of these secondary motions. We show that the formation of secondary flows is not very sensitive to the Reynolds number range investigated, and direct numerical simulations and experiments produce similar results in the mean flow as well as the dispersive and turbulent stress distributions. The numerical methods capture time-resolved features of the instantaneous flow and provide insight into the near-wall flow structures, that were previously obscured in the experimental measurements. Proper orthogonal decomposition was shown to capture the essence of the secondary flows in relatively few modes and to be useful as a filter to analyse the instantaneous flow patterns. The secondary flows are found to create extended regions of high Reynolds stress away from the wall that comprise predominantly sweeps similar to what one would expect to see near the wall and which are comparable in magnitude to the near-wall stress. Analysis of the instantaneous flow patterns reveals that the secondary flows are the result of a non-homogeneous distribution of mid-size vortices.

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The instantaneous structure of secondary flows in turbulent bounday layers - Accepted Manuscript
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Accepted/In Press date: 23 November 2018
e-pub ahead of print date: 16 January 2019
Published date: 10 March 2019

Identifiers

Local EPrints ID: 426476
URI: http://eprints.soton.ac.uk/id/eprint/426476
ISSN: 0022-1120
PURE UUID: 95b99b5f-6494-4aed-bb7e-43f93b52b922
ORCID for B. Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 28 Nov 2018 17:30
Last modified: 07 Oct 2020 04:29

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