Secondary flows in boundary layers over streamwise-aligned wall-roughness
Secondary flows in boundary layers over streamwise-aligned wall-roughness
The cause of recently observed spanwise-alternating low- and high-momentum pathways [1,2,3] to appear across the entire turbulent boundary layer formed over rough surfaces is experimentally investigated by measuring the flows over roughness elements with systematically varied spanwise spacing. We found that the secondary flows associated with these low- and high-momentum pathways only appeared when the spanwise spacing of roughness elements was roughly proportional to the boundary layer thickness, and did not appear for cases with spacing much less than the boundary layer height. This suggests that the ratio of the spanwise spacing to the boundary layer thickness, as opposed to the roughness height (or width), is the most important parameter to predict the occurrence of these secondary motions in turbulent boundary layers over rough walls.
Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
2015
Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Vanderwel, Christina and Ganapathisubramani, Bharathram
(2015)
Secondary flows in boundary layers over streamwise-aligned wall-roughness.
15th European Turbulence Conference, ETC 2015, , Delf, Netherlands.
25 - 28 Aug 2015.
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Conference or Workshop Item
(Paper)
Abstract
The cause of recently observed spanwise-alternating low- and high-momentum pathways [1,2,3] to appear across the entire turbulent boundary layer formed over rough surfaces is experimentally investigated by measuring the flows over roughness elements with systematically varied spanwise spacing. We found that the secondary flows associated with these low- and high-momentum pathways only appeared when the spanwise spacing of roughness elements was roughly proportional to the boundary layer thickness, and did not appear for cases with spacing much less than the boundary layer height. This suggests that the ratio of the spanwise spacing to the boundary layer thickness, as opposed to the roughness height (or width), is the most important parameter to predict the occurrence of these secondary motions in turbulent boundary layers over rough walls.
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Published date: 2015
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© TU Delft.
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15th European Turbulence Conference, ETC 2015, , Delf, Netherlands, 2015-08-25 - 2015-08-28
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Local EPrints ID: 491628
URI: http://eprints.soton.ac.uk/id/eprint/491628
PURE UUID: 8224d29e-4ee3-4f3e-95cb-e08950ab5e5f
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Date deposited: 03 Jul 2024 09:09
Last modified: 11 Jul 2024 01:53
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