The Ahmed Model Unsteady Wake: Experimental and Computational Analyses
2003-01-1315
03/03/2003
- Event
- Content
- 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.
- Pages
- 14
- 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.