Session: 03-09-02 Turbulent Flows (2/3)

Paper Number: 87396

87396 - Effect of the Rear Geometry on the Flow Structure and Drag of the Ahmed Body 

There is the need for fuel-efficient vehicles to save finite fossil fuel resources and minimize the range problem of modern electric vehicles, as well as combat the negative impact of global climate change. 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 and semi-circular surfaces to study the effect of these geometries on aerodynamic performance. The study is conducted using the 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 and semi-circular geometries reduced the drag by up 10% compared with the classic rectangular geometry. The cause of 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 base model, where it exits away from the vertical base. Similarly, the wake splits up into two after the reverse flow region in the streamwise direction. The connection between wake splitting and drag reduction is not reported in the literature. Therefore, this study will provide a detailed investigation into wake modification and analyses of the drag reduction processes.

Presenting Author: Naseeb Ahmed Siddiqui Ontario Tech University