GENERAL MOTORS
How The Chevy Volt Got In Shape
Many view the Chevrolet Volt as the next step in the evolution of the automobile. The Volt is an extended range electric vehicle: it can reach an initial 40 miles solely on battery power, from which point, the backup engine powers the electric generator for hundreds of additional miles. Able to re-charge the battery from a standard wall outlet, many drivers will never use a drop of gasoline in their daily commutes, yet the extended range is there whenever needed., Maximizing battery life and energy efficiency were fundamental goals to meet these mileage requirements of this unique vehicle, and aerodynamics played a crucial role in that quest. Nina Tortosa and Ken Karbon of General Motors Aerodynamics Staff report
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hiLe the Vo l t ’s propu lsion system doesn’t directly affect its shape efficiency, it does make aerodynamics much more important than in traditional vehicles. Aerodynamic performance is the second largest contributor to electric range, behind vehicle mass. Therefore, it was critical to reduce aerodynamic drag as much as possible while maintaining the key styling cues from the original concept car shown to critical acclaim in January 2007. This presented a number of challenges during the development, such as evaluating drag due to underbody features, balancing aerodynamics with wind noise and cooling flow, and interfacing with other engineering requirements. These issues were resolved by spending hundreds of hours in the wind tunnel and running numerous computational fluid Dynamics (cfD) analyses.
2010 | WIND TUNNEL INTERNATIONAL
The Chevrolet Volt is currently the lowest drag vehicle in General Motor’s lineup
Reduced scale (1:3) testing developed most of the Volt’s aerodynamic shape. Stereo lithography parts enhanced the clay model fidelity
WiND TuNNEL TESTiNG Since physical testing still provides the most accurate measurement of coefficient of drag (CD), the wind tunnel was the primary tool for development of the Volt exterior surface. Another significant advantage to wind tunnel testing is the quick turnaround in design changes. On average, fifteen design iterations were evaluated in a single eighthour shift. This provided rapid feedback to modifications in specific vehicle features. Wind tunnel testing started with a 1/3-scale clay model of the concept car’s design, proportioned to fit on to GM’s small car platform. 25