Daryakenari, B., Abdullah, S., and Zulkifli, R., "Reducing Vehicle Drag Force Through a Tapered Rear Side Wall," SAE Int. J. Commer. Veh. 6(2):582-588, 2013, doi:10.4271/2013-01-9020.
Recent fluctuation in oil prices has generated interest in fuel-efficient vehicles, especially their aerodynamic profile. The literature indicates that turbulent wakes that form at the rear end of the vehicle contribute to vehicle drag in a major way. Minor studies have addressed the effects of rear-end wall angle to the drag force through effecting the wake behind the vehicle; however, this study assesses the reduction of drag using angular side walls. A previous simulation of external airflow over Ahmed's body was investigated, utilizing the k-ω SST models. Different angles of side walls were analyzed, and a maximum 36.85% reduction in drag coefficient was achieved using an angular rear side wall. The turbulent model was validated and the effectiveness of angular rear side walls thus proven. The study then simulated the flow for a road vehicle model to investigate the real world effect of angular rear side walls. The results showed up to 11.39% reduction in drag coefficient, supporting the effect of angular rear walls on reducing drag coefficient.