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Active drag reduction of a high-drag Ahmed body based on steady blowing

Published online by Cambridge University Press:  04 October 2018

B. F. Zhang Open the ORCID record for B. F. Zhang [Opens in a new window] ,
K. Liu ,
Y. Zhou ,
S. To  and
J. Y. Tu
B. F. Zhang
Affiliation:
Institute for Turbulence-Noise-Vibration Interactions and Control, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China State Key Laboratory of Ultra-precision Machining Technology, Department of Industrial and System Engineering, The Hong Kong Polytechnic University, Hong Kong
K. Liu
Affiliation:
Institute for Turbulence-Noise-Vibration Interactions and Control, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong
Y. Zhou*
Affiliation:
Institute for Turbulence-Noise-Vibration Interactions and Control, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China Digital Engineering Laboratory of Offshore Equipment, Shenzhen, China
S. To
Affiliation:
State Key Laboratory of Ultra-precision Machining Technology, Department of Industrial and System Engineering, The Hong Kong Polytechnic University, Hong Kong
J. Y. Tu
Affiliation:
School of Engineering, RMIT University, Melbourne 3001, Australia
*
†Email address for correspondence: [email protected]
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Abstract

Active drag reduction of an Ahmed body with a slant angle of $25^{\circ }$, corresponding to the high-drag regime, has been experimentally investigated at Reynolds number $Re=1.7\times 10^{5}$, 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.

JFM classification

Flow Control: Flow Control Wakes/Jets: Separated flows Wakes/Jets: Wakes
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 856 , 10 December 2018 , pp. 351 - 396
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Copyright
© 2018 Cambridge University Press 

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