The Ahmed Model Unsteady Wake: Experimental and Computational Analyses 2003-01-1315
The unsteady wake of the Ahmed model has been investigated experimentally using time-accurate 5-hole and hot-wire probes and computationally using Exa PowerFLOW. The backlight angle was 25° which was chosen to be slightly below the critical angle observed computationally. The CFD results are similar to experimental results for backlight angles just below the critical angle (eg: 27.5°, 30°). Unsteady flow-field reconstruction of the experimental results and the CFD results both revealed a quasi-two-dimensional vortex-shedding type structure from the bottom of the model base. This results in a semi-periodic build up and collapse of the near wake and produces a symmetric oscillation in the strength and position of the rear pillar vortices. The period of this phenomenon corresponds to a Strouhal number of approximately 0.5 based on free-stream velocity and the square root of the model frontal area.
Citation: Sims-Williams, D. and Duncan, B., "The Ahmed Model Unsteady Wake: Experimental and Computational Analyses," SAE Technical Paper 2003-01-1315, 2003, https://doi.org/10.4271/2003-01-1315. Download Citation
Author(s):
David B. Sims-Williams, Bradley D. Duncan
Affiliated:
University of Durham, Automotive Aerodynamics
Pages: 14
Event:
SAE 2003 World Congress & Exhibition
ISSN:
0148-7191
e-ISSN:
2688-3627
Also in:
Vehicle Aerodynamics 2003-SP-1786, SAE 2003 Transactions Journal of Passenger Cars - Mechanical Systems-V112-6
Related Topics:
Computational fluid dynamics
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