Numerical Study of the Generic Sports Utility Vehicle Design with a Drag Reduction Add-On Device

CFD simulations using ANSYS FLUENT 6.3.26 have been performed on a generic SUV design and the settings are validated using the experimental results investigated by Khalighi. Moreover, an add-on inspired by the concept presented by Englar at GTRI for drag reduction has been designed and added to the generic SUV design. CFD results of add-on model and the basic SUV model have been compared for a number of aerodynamic parameters. Also drag coefficient, drag force, mean surface pressure, mean velocities, and Cp values at different locations in the wake have been compared for both models. The main objective of the study is to present a new add-on device which may be used on SUVs for increasing the fuel efficiency of the vehicle. Mean pressure results show an increase in the total base pressure on the SUV after using the device. An overall reduction of 8% in the aerodynamic drag coefficient on the add-on SUV has been investigated analytically in this study. 1. Introduction Sports utility vehicles are known worldwide for their ruggedness and high passenger capacity. Their ability to run on both off-road and on-road conditions makes them very peculiar for usage. Due to their high utility, a need for making them more fuel efficient has arisen in the past few years. The following data shows the average miles per gallon statistics for cars and SUVs. The increase in the fuel efficiency is due to improvements in the aerodynamics of the automobiles. For the SUVs the average miles per gallon has been fairly increasing in the past few years as shown in Figure 1. The need of lowering down the aerodynamic drag on the SUVs in order to further increase the average miles per gallon has been the issue for the future work. Figure 1: Average miles per gallon for automobiles in US from 1970 to 2006. Aerodynamic effects on a running SUV play a substantial role in their fuel efficiency. Efforts have been made for making the SUVs aerodynamically and fuel efficient by using a variety of add-on devices and other methods. Shape cannot be much compromised for the basic purpose of the SUV. Hence methods to alter the air flow over the surface of the SUV by using devices or by blowing air in the rear region of the SUV are widely used for drag reduction. Form drag or the pressure drag contributes to the 90% of the total drag [1] on the bluff bodies and can be reduced using the add-on devices. A great amount of research has been done in the field of add-on devices on SUVs and pick-up trucks for reduction in drag forces by altering the air flow around and behind the vehicle. Some of the