Aerodynamic Shape Optimization of Simplified Ground Vehicle (Ahmed Body) using Passive Control Devices

Abstract

The present study aims to control the flow separation on the simplified ground vehicle (Ahmed Body) utilizing cylindrical roughness elements and vortex generators (VG) as passive control devices. To simulate the flow over the solid body, the Computational Fluid Dynamics (CFD) method was used and combined with aerodynamic shape optimization applied concurrently to obtain the optimal dimensions and position of the passive control devices. Firstly, aerodynamic analysis methodology was validated by conducting also mesh independence study with experimental results from the literature. Later on, by changing the slant surface angle of the model, the analyses were performed to indicate different scenarios and the results were presented visually for each case. Aerodynamic shape optimization is performed using a Genetic Algorithm (GA) on DesignXplorer in ANSYS to find the optimum size and location of the passive control devices that minimize drag force, as an objective. Consequently, the flow separation of the rear end of the body was found to be delayed or suppressed and vortex height is to be reduced thanks to the applied passive control devices. The total drag reduction was achieved by about 10.72%, and 13.37% for the optimal shape and location of the cylindrical roughness elements and VG devices, respectively, comparing to the baseline model.