Analysis of Novel Techniques of Drag Reduction and Stability Increase for Sport Utility Vehicles using Computational Fluid Dynamics

The main objective of this study is to investigate ways to reduce the aerodynamic drag coefficient and to increase the stability of road vehicles using three-dimensional Computational Fluid Dynamics (CFD) simulation. Two baseline models, the Ahmed body and the Land Rover Discovery 4, were used in these simulations. The effects of model scale and slant angle were investigated for the Ahmed body in addition to a new technique to measure the drag coefficient used in the experiments has been investigated numerically in this study. Many new aerodynamic devices and external design modifications were used for the Land Rover Discovery 4. ANSYS Meshing was used to create a variety of mesh cases for mesh optimization and ANSYS Fluent software was used to simulate all models. Different sizes of computational domain were used in order to study the effect of the blockage ratio on the aerodynamic behaviour. The range of Reynolds numbers used in this study for the Ahmed body was between 3 × 105 and 30 × 105 similar to the experimental studies. The uniform free stream velocity of air at the inlet ranging from 100km/h to 140km/h was used for the Land Rover Discovery 4. Reynolds-averaged Navier–Stokes equations (RANS) and Large Eddy Simulation (LES) turbulence models were used to establish the most appropriate turbulence model for the Ahmed body geometry. Only RANS was used for the Land Rover Discovery 4. In general, the trend of drag coefficient as a function of the Reynolds number for the Ahmed body was in good agreement with the experiments, whereas LES simulation results were closer to the experimental data. The drag and lift coefficients obtained from ANSYS Fluent for the baseline of the Land Rover Discovery 4 were validated with experimental data. It is found that the use of modern aerodynamic add-on devices and modifications has a significant effect in reducing the aerodynamic drag coefficient.