Hybrid Flow Control of a Square-Back Ahmed Body Using Perforated Flaps and Synthetic Jet Actuation

As heavy-duty vehicles and emission regulations are becoming more stringent, it is very important to pursue and develop technological advancements to tackle the scarcity of fossil fuels and emissions. To address this issue, this paper aims to investigate the effect of hybrid flow control methods on the coefficient of drag for an Ahmed body. In this study, four distinct types of flaps were tested to determine the most effective geometry for drag reduction compared to the baseline value obtained using in-house experiments. Next, the synthetic jet actuation (SJA) is incorporated into the configuration to understand the effect of forcing on the coefficient of drag. This study proposes a novel two-stage hybrid flow-control strategy combining a perforated panel with SJA for aerodynamic reduction in a square-back Ahmed body. In the first stage, the perforated panel passively modifies the flow immediately upstream of the base region, attenuating the momentum and energetic flow structures entering near the wake and thereby promoting a more favorable wake state. In the second stage, synthetic jet actuators actively manipulate the conditioned wake to further enhance pressure recovery and reduce aerodynamic drag. This sequential passive–active approach is intended to reduce the actuation demand placed on the synthetic jets while achieving greater overall drag reduction than an exclusively active flow-control strategy. For the passive control cases the elliptic flap with holes achieved 9.38% drag reduction compared to the baseline. For the hybrid control case combining both passive control and SJA, this value increased to 12.34%.