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Nomenclature
A area (m2 )
b standard systematic uncertainty
CD drag coefficient
CL lift coefficient
FD drag force (N)
FL lift force (N)
L length (m)
M number of measured data points
P pressure (kPa)
r experimental results
Re Reynolds number
s standard deviation
U overall uncertainty
V velocity (m/s)
Xi measurements of the i th variable
Greek symbolsρ density (kg/m3 )
μ viscosity (kg/m-s)
τij shear-stress tensor (N/m2 )
Π dependent variable
1. Introduction
Today, due to economical, safety and even environmental concerns, vehicle aerodynamics play a much more significant role in design considerations than it did before. It is estimated that the aerodynamic drag is the governing form of resistance when vehicles reach speeds of 80 km/h or greater, especially considering the fact that 65 percent of the power required at 110 km/h is consumed due to overcoming aerodynamic drag ([1] Leduc, 2009; [2] Diamond, 2004). Therefore the improvements in aerodynamic characteristics can result in significant decrease in driving stability, handling, fuel consumption and overall efficiency. Thus, it is no surprise that rear spoilers are becoming more widely used in the auto industry. With increasing in the oil prices and more stringent legal regulations, more research is conducted on accessories that can improve the vehicle's fuel efficiency. Among these accessories, rear spoilers are one of the major ones due to being relatively inexpensive, easy to install and aesthetically appealing. Furthermore, it can reduce the drag coefficient and increase the fuel efficiency significantly for most passenger vehicles, while decreasing the lift coefficient in the expense of the drag coefficient in most race cars. However, the benefits of the rear spoiler are not limited only to fuel cost. By also deflecting the traveling air upwards by increasing the pressure rear deck, the rear spoiler can provide better traction, faster turning, acceleration and brake as well as increasing the vehicle safety.
Even though the rear spoiler is one of the key players in vehicle aerodynamics, there are only limited amount of associated studies in the literate that incorporates both the computational analysis and experimental verification. The studied vehicles vary from mini-vans to modified race cars and are analyzed for various purposes such as improving aerodynamic and...