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DFE World: Design & the Global Environment
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Exercises


Aerodynamic Design


 

 

 

Vehicle Design

 

Drag Force

Optimizing aerodynamic drag not only reduces fuel consumption, but it can also increase vehicle performance at high speeds and lower aerodynamic noise.  At high speeds, most fuel is utilized to overcome the aerodynamic drag force, the resistance created by the air flow.  Aerodynamic resistance is created from pressure resistance due to vehicle shape, air friction resistance over the vehicle surface, and density resistance from extruding parts (ie. mirrors) and internal vehicle ducts.  The greatest effect (70%) is caused by pressure resistance which depends on many vehicle design factors such as the front spoiler, the shape of the vehicle front, the angle of inclination of the rear window and the shape of the vehicle rear. 

 

Wind Tunnel Testing with Lamborghini to determine Aerodynamic Performance

 

The Drag force value for a moving vehicle is given by the following expression:

 

         D = *CD*A*ρ*V2

 

Where

o        CD is the drag coefficient

o        A is the projected frontal area of the vehicle

o        ρ is the density of air

o        V is the speed of the vehicle relatively to the air

 

Lowering the drag through vehicle design will reduce vehicle drag and optimize fuel economy.  Since frontal area is usually pre-determined for a certain vehicle program, lowering the drag coefficient through an aerodynamic design offers the best opportunity to reduce vehicle drag and therefore optimize fuel economy.