Influence of the rounded rear edge on wake bi-stability of a notchback bluff body

The wake bi-stability behind notchback Ahmed bodies is investigated by performing wind tunnel experiments and large eddy simulations (LESs). The focus of this study is on the suppression of bi-stable wakes achieved by rounding the roof's trailing edge of the body. The sup- pression effect is found to depend on the Reynolds number (Re). The wake behind a sharp edge remains bi-stable for all tested Re. However, for a rounded edge with small radius, wake bi-stability at Re¼ 0:5 105 and wake symmetrization with 0:75 105 Re 1:5 105 are observed. Increasing Re with Re 1:75 105, the wake returns to the bi-stable state. Particularly, with Re 2 105, a stable asymmetric wake state with no switches is observed for long periods. Performing LES confirms the expected wake asymmetry at Re¼ 0:5 105 and sym- metry at Re¼ 1 105 for the case of rounded edge with a small radius. Besides, another wake symmetry is observed for the rounded edge with a large radius at Re¼ 0:5 105. For the two wake symmetries shown in the LES results, the symmetrization is attributed to wake sup- pression in the notchback region, forcing the flow separation from the rear roof to attach to the slant on both sides of the body.