Numerical investigation of the wake bi-stability behind a notchback Ahmed body
Journal article, 2021

Large-eddy simulations are used to investigate the origin of the wake asymmetry and symmetry behind notchback Ahmed bodies. Two different effective backlight angles, beta(1) = 17.8 degrees and beta(2) = 21.0 degrees, are simulated resulting in wake asymmetry and symmetry in flows without external perturbations, in agreement with previous experimental observations. In particular, the asymmetric case presents a bi-stable nature showing, in a random fashion, two stable mirrored states characterized by a left or right asymmetry for long periods. A random switch and several attempts to switch between the bi-stability are observed. The asymmetry of the flow is ascribed to the asymmetric separations and reattachments in the wake. The deflection of the near-wall flow structures behind the slant counteracting the asymmetry drives the wake to be temporarily symmetric, triggering the switching process of the bi-stable wake. The consequence of deflection that forces the flow structure to form on the opposite side of the slant is the decisive factor for a successful switch. Modal analysis applying proper orthogonal decomposition is used for the exploration of the wake dynamics of the bi-stable nature observed.

wakes

Author

Kan He

Central South University

National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle

Guglielmo Minelli

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

Jiabin Wang

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

Tianyun Dong

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

Guangjun Gao

Central South University

National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle

Sinisa Krajnovic

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

Journal of Fluid Mechanics

0022-1120 (ISSN) 1469-7645 (eISSN)

Vol. 926 A36-1-A36-29 A36

Subject Categories

Ocean and River Engineering

Other Physics Topics

Fluid Mechanics and Acoustics

DOI

10.1017/jfm.2021.748

More information

Latest update

9/29/2021