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What is the proper wind speed to find the drag coefficient of a car in a wind tunnel? Answered

This is part of a high school project in which students are comparing the Cd of a full size car with the Cd of a 1:64 (Howwheel size) toy car

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kelseymh (author)2010-01-29

According to Wikipedia (their physics articles are generally good), the drag coefficient is dimensionless, and scales inversely with both the frontal area and the wind velocity squared.  You could have found this by typing "drag coeffcient" into Wikipedia's search box.  You'll also find a separate article specific to automobile drag.

Because of the scaling, you will need to use a wind velocity scaled by 1/642, or about 1/1000, compared to real world conditions.

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Kiteman (author)2010-01-29

Two choices: same-speed wind, or scale-speed wind.

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