There is a need for fuel-efficient vehicles to reduce greenhouse emission and minimize the range problem of electric vehicles. Aerodynamic drag reduction provides one of the cheapest but effective alternatives. Therefore, the development and analysis of new passive strategies that can modify the flow structure to improve aerodynamic performance are much needed. The present study aims to provide a passive drag reduction method using the standard 35° Ahmed body. The classic rectangular slanted surface is replaced with elliptical to study the effect of reear geometry on aerodynamic performance. The study is conducted using the ANSYS FLUENT software at a Reynolds number of 7.8 × 105, based on the height of the model. The SST k-omega model is applied to solve the Navier-Stokes equations. The results show that the elliptical model reduced the drag by 10% compared to the classic rectangular geometry. The cause of this drag reduction is associated with the large modification of the flow structure in the wake region. Also, the reverse flow is observed to shift towards the vertical base compared to the standard model, where it exits away from the vertical base. The drag reduction is found to correlated with the recirculation modification. Therefore, this study provides detailed data and analysis of wake modification and drag reduction processes.

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