Control of circular cylinder flow using distributed passive jets
Author(s)
Clapperton, Ben
Bearman, PW
Type
Journal Article
Abstract
A wind tunnel study has been carried out to investigate flow control around a hollow circular cylinder using passive jets driven by naturally occurring pressure differences. Flow enters the cylinder through spanwise holes along the stagnation line and exits through a spanwise distribution of holes at ±65∘ . The diameter of the entry and exit holes were 1 % and 0.5 % of the cylinder diameter, respectively. Reynolds numbers were at the upper end of the subcritical regime and ranged from 3×104 to 2.8×105 . Jet spacings of 10 % and 20 % of the cylinder diameter were investigated, and the ratio of the average jet exit velocity to the cross-flow velocity at the boundary layer edge was found to rise to approximately 0.35 and 0.4, respectively, above a Reynolds number of 1.5×105 . Findings based on using the surface oil flow technique revealed a repeating, organised cellular pattern downstream of adjacent jet exit holes consisting of a primary counter-rotating vortex pair structure, followed by a secondary weaker pair. Downstream of adjacent exit holes, and centred midway between them, there exists a separation bubble which delays final flow separation compared with the flow directly downstream of a jet. The variation in the angular position of boundary layer separation across the span had the effect of suppressing von Kármán vortex shedding. This resulted in a drag coefficient, at the upper end of the Reynolds-number range studied, 14.5 % lower than that found using trip wires to initiate boundary layer transition.
Date Issued
2018-08-10
Date Acceptance
2018-05-01
Citation
Journal of Fluid Mechanics, 2018, 848 (1), pp.1157-1178
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
1157
End Page
1178
Journal / Book Title
Journal of Fluid Mechanics
Volume
848
Issue
1
Copyright Statement
© 2018 Cambridge University Press. This paper has been accepted for publication and will appear in a revised form, subsequent to peer-review and/or editorial input by Cambridge University Press.
Identifier
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/control-of-circular-cylinder-flow-using-distributed-passive-jets/C00A3A8DCE736091C43BA4CCDF2A4BE0
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
boundary layer separation
drag reduction
flow control
CROSS-FLOW
3-DIMENSIONAL SEPARATION
REYNOLDS-NUMBER
TRANSVERSE JET
PRESSURE
TOPOLOGY
PATTERNS
DRAG
WAKE
Fluids & Plasmas
01 Mathematical Sciences
09 Engineering
Publication Status
Published
Date Publish Online
2018-06-13