The Effect of Different Dimple Sizes on the Drag Force on a Car

The purpose of this experiment was to determine if the addition of dimples to a car’s surface would result in the reduction of drag force acting on the car, and the effect of dimple size on that drag reduction. This experiment attempted to support the theory that dimples on a car reduce drag, in a similar manner to how dimples reduce drag acting on a golf ball.

This experiment was conducted using a homemade car. This car had the ability to be dimpled with either six millimeter, eight millimeter, or ten millimeter dimples. The car was placed inside a wind tunnel and attached to a force sensor. The force over time was recorded on a Lab Quest, and the average of the forces when the reading “leveled off” and became constant was taken.

During the experiment, it was observed that the drag forces for all car types were not equal, as proven with an ANOVA test that had a p-value of essentially zero. Multiple two-sample t tests were used to see if a particular car type was more effective than the others. The only dimpled car type that had a statistically significant reduction in drag force was the eight millimeter dimple. Two-sample t-tests were conducted with the eight millimeter dimple car and all other car types, which resulted in significantly low p-values. All other dimple sizes actually increased the drag force.

These results can help with reducing oil consumption and dependence. There is a push from the government and consumers for increased fuel efficiency in cars. A dimpled car design could be an easy way to reduce drag force, and increase fuel efficiency.

Research Done By:

Josh Denzler
Lake Shore High School

Michael Oliver
Lake Shore High School