Active Drag Reduction Of A High-Drag Ahmed Body Based On Steady Blowing

Zhang, B, Liu, K, Zhou, Y, To, S and Tu, J 2018, 'Active Drag Reduction Of A High-Drag Ahmed Body Based On Steady Blowing', Journal of Fluid Mechanics, vol. 856, pp. 351-396.


Document type: Journal Article
Collection: Journal Articles

Title Active Drag Reduction Of A High-Drag Ahmed Body Based On Steady Blowing
Author(s) Zhang, B
Liu, K
Zhou, Y
To, S
Tu, J
Year 2018
Journal name Journal of Fluid Mechanics
Volume number 856
Start page 351
End page 396
Total pages 46
Publisher Cambridge University Press
Abstract Active drag reduction of an Ahmed body with a slant angle of 25 degrees, corresponding to the high-drag regime, has been experimentally investigated at Reynolds number Re = 1 : 7 X 105, based on the square root of the model cross-sectional area. Four individual actuations, produced by steady blowing, are applied separately around the edges of the rear window and vertical base, producing a drag reduction of up to 6-14 %. However, the combination of the individual actuations results in a drag reduction 29 %, higher than any previous drag reductions achieved experimentally and very close to the target (30 %) set by automotive industries. Extensive flow measurements are performed, with and without control, using force balance, pressure scanner, hot-wire, flow visualization and particle image velocimetry techniques. A marked change in the flow structure is captured in the wake of the body under control, including the flow separation bubbles, over the rear window or behind the vertical base, and the pair of C-pillar vortices at the two side edges of the rear window. The change is linked to the pressure rise on the slanted surface and the base. The mechanisms behind the effective control are proposed. The control efficiency is also estimated.
Subject Numerical Modelling and Mechanical Characterisation
Keyword(s) flow control
separated flows
wakes
DOI - identifier 10.1017/jfm.2018.703
Copyright notice © Cambridge University Press 2018
ISSN 0022-1120
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