Abstract
Road vehicles such as SUVs or pickup trucks are described as blunt bodies. When the airflow passes over a road vehicle, the flow will separate at the rear of the vehicle, forming a large low-pressure turbulent wake region behind it. The formed pressure drag posts resistance on a road vehicle and thus increases the work done by the engine to propel the vehicle. The purpose of this thesis is to present the development, design, and design optimization of drag reducing devices for SUVs by studying the SUV's aerodynamics. Numerical simulations using commercial software package -FLUENT were performed in order to study the aerodynamics behind the vehicles. A computer model, the Ahmed Reference Model, was selected as a benchmark test. The Ahmed Reference Model is an aerodynamic test vehicle with a simple geometric body that retains the major flow features where most part of the drag is concentrated. Computational fluid dynamic (CFD) simulations for the eight SUV models were performed and their performance was analyzed. The eight CFD models consisted of one SUV model without a drag reducing device and seven SUV models with drag reducing devices of different designs. Vehicle spoilers were used as the drag reducing devices. The SUV's aerodynamics for the seven different spoiler designs has been presented through velocity vectors, pressure contours, and aerodynamic lift and drag plots. Some spoiler designs were able to reduce aerodynamic drag and others were able to reduce aerodynamic lift. SUV Spoiler 7 Model yielded the highest aerodynamic drag reduction; therefore, the design for Spoiler 7 was optimized. A fuel economy analysis of the optimized Spoiler 7 design was also performed to measure the impact of the aerodynamic drag reduction on fuel economy over the US. EPA driving schedules and significant conclusions were drawn.