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The influence of background turbulence on Ahmed-body wake bistability

Published online by Cambridge University Press:  06 September 2021

D. Burton ,
S. Wang ,
D. Tudball Smith ,
H. N. Scott ,
T. N. Crouch  and
M. C. Thompson
D. Burton*
Affiliation:
Monash Wind Tunnel Research Platform, Monash University, Clayton, VIC 3800, Australia Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Monash University, Clayton, VIC 3800, Australia Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
S. Wang
Affiliation:
Monash Wind Tunnel Research Platform, Monash University, Clayton, VIC 3800, Australia Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Monash University, Clayton, VIC 3800, Australia Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
D. Tudball Smith
Affiliation:
Monash Wind Tunnel Research Platform, Monash University, Clayton, VIC 3800, Australia Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Monash University, Clayton, VIC 3800, Australia Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
H. N. Scott
Affiliation:
Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
T. N. Crouch
Affiliation:
Monash Wind Tunnel Research Platform, Monash University, Clayton, VIC 3800, Australia Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Monash University, Clayton, VIC 3800, Australia Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
M. C. Thompson
Affiliation:
Monash Wind Tunnel Research Platform, Monash University, Clayton, VIC 3800, Australia Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Monash University, Clayton, VIC 3800, Australia Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
*
†Email address for correspondence: david.burton@monash.edu
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Abstract

The discovery of wake bistability has generated an upsurge in experimental investigations into the wakes of simplified vehicle geometries. Particular focus has centred on the probabilistic switching between two asymmetrical bistable wake states of a square-back Ahmed body; however, the majority of this research has been undertaken in wind tunnels with turbulence intensities of less than $1\,\%$, considerably lower than typical atmospheric levels. To better simulate bistability under on-road conditions, in which turbulence intensities can easily reach levels of $10\,\%$ or more, this experimental study investigates the effects of free-stream turbulence on the bistability characteristics of the square-back Ahmed body. Through passive generation and quantification of the free-stream turbulent conditions, a monotonic correlation was found between the switching rate and free-stream turbulence intensity.

JFM classification

Wakes/Jets: Wakes Vortex Flows: Vortex shedding Wakes/Jets: Separated flows

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Type
JFM Rapids
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Journal of Fluid Mechanics , Volume 926 , 10 November 2021 , R1
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Copyright
© The Author(s), 2021. Published by Cambridge University Press

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References

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Burton et al. supplementary movie 1

Bistable state switching of the square-back Ahmed body wake under low (~1%) turbulent flow conditions.

Download Burton et al. supplementary movie 1(Video)
Video 26.8 MB

Burton et al. supplementary movie 2

Bistable state switching of the square-back Ahmed body wake under high (13%) turbulent flow conditions.

Download Burton et al. supplementary movie 2(Video)
Video 30.8 MB