Suppression of the wake steady asymmetry of an Ahmed body by central base bleed

Base blowing is applied through a small, centrally located square aperture at the base of a flat-backed Ahmed body. In addition to the expected drag reduction effect at low momentum injection (i.e., base bleeding effect), a major result is the complete suppression of the steady asymmetry of the wake. Both the maximum drag reduction and the minimum magnitude of the base pressure gradient are achieved for the same optimal blowing coefficient of the actuator. Independent force measurements corroborate the suppression of the wake asymmetry. Different scales of base blowing reveal a similar maximum drag reduction and asymmetry suppression, where the optimal blowing coefficient is found to scale with the bleed-to-base area ratio as (Sj/S)1/2.