Abstract
A series of three-dimensional time-dependent numerical simulations of the flow around the Ahmed Body were conducted for the case of a slant angle 𝜃= 29° and the range of the Reynolds number Re ⩽ 2000. The critical Reynolds number for the transition from the steady to the oscillatory flow was found to be Rec = 1751. The oscillatory flow appearing near Rec is of the single frequency oscillatory flow, which has the peak frequency of the Strouhal number St ≈ 0.07. For the higher Re the multiple frequency oscillatory flows are found, and the transition from the single to multiple oscillation can be predicted in the range 1800 < Re ⩽ 1900. The kinetic energy of the deviated oscillatory flow field is supplied from the time-averaged flow field strongly near the pair of the vertical vortices and near the rear wall of the body. As one possibility, the instability mechanism acting near the vertical vortices may have some similarity with known centrifugal instability.
