Passive flow control on Ahmed body by rear linking tunnels

This paper concentrates on the interaction of a car body with the surrounding airflow, in order to provide small changes for reducing vehicle fuel consumption by reducing drag. There are many passive and active methods for this purpose, the main goal of this project is the development of passive drag reduction devices for the simplified reference model (Ahmed body with 25°, 30°, and 35° slant angle) used to represent bluff body vehicles. Passive flow control is performed by adding linking tunnels at the rear of the bluff body, blowing the flow from the sidewalls (high-pressure zone) to the wake region (low-pressure zone). The movement of a high-pressure flow to the wake zone reduces the wake size, which reduces the pressure drag. A numerical and experimental analysis of this passive method is carried out. The optimal configuration was reached by numerical analysis (showing a drag reduction of up to 5%) and after that, experimental tests were performed in a wind tunnel to check the effect of this passive flow control on an Ahmed body 25°.