Active Flow Control for Drag Reduction of a Square-back Car Model

Abstract, Dissertation Robin Placzek Active Flow Control for Drag Reduction of a Square-back Car Model For an emission reduction of passenger cars, more emphasis needs to be put on aerodynamic designs and enhanced drag reduction methods. In general, minimizing a highly dissipative wake structure holds a high potential for a major drag reduction. Therefore, numerous studies investigated and proved the feasibility of active flow control concepts to actuate the wake flow of generic bluff-bodies and generic vehicles in order to reduce drag. To contribute to scientific knowledge, the present study investigates the feasibility of an active flow control concept, which utilizes tangential Coanda wall jets, to actuate the wake flow of a detailed production car model. The flow control approach combines a boat-tailing concept with the integration of the Coanda jets in the range of the vehicle rear. Due to the realistic geometry considered, different active devices, such as an active diffuser and an active wheelhouse, were designed for an optimized actuation all around the base. The additional energy input for operating the pressurized Coanda jets was also a crucial point for adjusting the jet amplitude and for an evaluation of the system efficiency. Since a power benefit represents the power that is saved, this study aimed at maximizing the power benefit. Experimental measurements were conducted to verify the numerical simulations, which were utilized for the concept design. The experiment showed a total drag reduction of 21.5%. About 11.6% could be attributed to passive geometry changes. Moreover, the active blowing experimentally generated a drag reduction of 11.2% at a power ratio of 2.6 and a power benefit of 6.9%. Subsequently, for a smaller design impact, a first approach of transferring a reduced concept to a full-scale production vehicle was investigated.