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 suppression effect is found to depend on the Reynolds number ( R e). The wake behind a sharp edge remains bi-stable for all tested R e. However, for a rounded edge with small radius, wake bi-stability at R e = 0.5 x 10(5) and wake symmetrization with 0.75 x 10(5) & LE; R e & LE; 1.5 x 10(5) are observed. Increasing R e with R e & GE; 1.75 x 10(5), the wake returns to the bi-stable state. Particularly, with R e & GE; 2 x 10(5), a stable asymmetric wake state with no switches is observed for long periods. Performing LES confirms the expected wake asymmetry at R e = 0.5 x 10(5) and symmetry at R e = 1 x 10(5) 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 R e = 0.5 x 10(5). For the two wake symmetries shown in the LES results, the symmetrization is attributed to wake suppression in the notchback region, forcing the flow separation from the rear roof to attach to the slant on both sides of the body.

Automated summary

The study investigates the wake bi-stability of notchback Ahmed bodies through wind tunnel experiments and large eddy simulations (LES). It is found that rounding the roof's trailing edge of the body can suppress bi-stable wakes, with the effect depending on the Reynolds number (Re). Different wake behaviors, such as bi-stability, symmetrization, and stable asymmetric wake states, are observed at different Reynolds numbers. LES results confirm the wake asymmetry and symmetries at specific Reynolds numbers, showcasing the influence of wake suppression in the notchback region.