A Master of Science thesis in Mechanical Engineering by Walid Ibrahim Mazyan entitled, "Numerical Simulations of Drag-Reducing Devices for Ground Vehicles," submitted in January 2013. Thesis advisor is Dr. Essam Wahba. Available are both soft and hard copies of the thesis.
The aim of the present study is to reduce the aerodynamic drag coefficient of ground vehicles. With the application of efficient drag reducing devices, aerodynamic drag is significantly reduced. This study analyzes numerically the effect of applying drag reducing devices on a sedan, sports utility vehicle (SUV) and a tractor trailer model to improve the fuel consumption of the vehicle. Both RANS (Reynolds-averaged Navier-Stokes equations) and LES (Large Eddy Simulations) are used to analyze the percent drag reduction due to the use of different drag reducing devices. The numerical procedure is first validated against the experimental data for the tractor-trailer model with no drag reducing devices installed. Following the validation, simulations are carried out to investigate the percent drag reduction by installing a modified front head to help the flow transition from the tractor to the trailer, and inventive rear wings that direct the air flow towards the rear of the vehicle where low pressure exists. The tractor trailer results showed a total drag reduction of around 21% when the front and rear drag reducing devices were installed. Vortex generators are also numerically simulated and results show that they reduce drag by 1.6%. The SUV model showed a drag reduction of 4.2 % and the Ahmed car model showed a drag reduction of 10 %. Results showed that the LES model provides the most accurate prediction of all turbulence models as compared to the experimental value of the drag coefficient. Keywords: Aerodynamics, Large Eddy Simulation, Reynolds-Averaged Navier-Stokes equations, Drag, Ground Vehicles.