Machine Design

CFD software helps shape a sports car

Recent years have seen the automobile industry relying more heavily on numerical methods for aerodynamic design and less on expensive experimental tests.

The Numa car was designed for sporty performance, so low drag and lift were critical. Ansys CFX showed designers how little details on the shape and position of spoilers and airfoils affected lift and drag and helped find a compromise between the two.

Take a project called the Numa car, for example. Engineers in the Dept. of Mechanical Engineering at the University of Coimbra in Portugal have been fine-tuning its shape through aerodynamic analyses using Ansys CFX computational-fluid-dynamics software. The software gives information on flow separation, pressure, velocity fields, along with vortices and forces acting on the vehicle.

For instance, designers positioned airfoils in the final design based on the visualized flow field at the rear of the vehicle. Pressurecoefficient charts helped define the overall geometry and illustrated the distribution of applied forces. Simulations employed a turbulence model built into the software. The final design cut drag by 5% over the original design and with a lower lift.

Research began on a sporty model and three possible rear ends. A mesh of boundary elements on the car's surface improved spatial resolution and gave a better understanding of boundary-layer phenomena. Unstructured tetrahedral elements were used for volume meshing. An aerodynamic-optimization feature helped find the best configuration of airfoils, spoilers, and diffusers.

Ansys Inc., (800) 937-3321,

TAGS: CAD Archive
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