Unsteady Flow Structure Behind A Low-Drag Ahmed Body
Unsteady flow structure behind an Ahmed body with a slant angle of 35°, corresponding to the low-drag regime, has been experimentally investigated at Re of 6.59 × 104. Measurements are conducted using single hotwire and flow visualization techniques. The major flow characteristics are examined. A total of five distinct Strouhal numbers (St) have been identified in the wake, as the case of the high-drag regime. Two detected over the rear window are linked to vortices generated along the roof and side surfaces of the model, respectively, and two found near the ground surface are ascribed to vortices produced by the struts (wheels) of the body. The fifth one, with St = 0.3, captured behind the base is distinct from its counterpart found in the high-drag regime and a physical explanation is proposed for this St.
KeywordsAhmed body wake Unsteady flow structure Vehicle model Strouhal number
Authors acknowledge support from the Hong Kong Scholar Program and China Postdoctoral Science Foundation through grants 2012M510874, 2012T50314 and 2014M551180. Supports from Research Grants Council of HKSAR through grant GRF 531912 and from Shenzhen Government through grant JCYJ20130329154125496 are also gratefully acknowledged.
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