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Old 07-09-2008, 12:37 AM   #4 (permalink)
pasadena_commut
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Join Date: Jul 2008
Location: California
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Quote:
Originally Posted by BamZipPow View Post
I know most aero mods are passive ones that use fixed structures to redirect/shape the airflow around the vehicle.
Funny you should mention that, I was thinking about something similar today.

What if a large part of the surface of a vehicle was moving with zero velocity with respect to the air? Normally of course the surface moves with the same velocity as the vehicle, but it does not have to. For instance, consider this thought experiment: on a big rectangular truck mount very light rollers on frictionless bearings perpendicular to the flow of air along the top and both of the long sides. The truck gets up to a constant speed and the rollers spin up until the outer surface of each roller is stationary with respect to the air. (Or the rollers could be spun up by tiny motors, the point is the the speed of the vehicle's surface changes.) The shape of the vehicle is (close) to unchanged, but the boundary condition has changed. What would this do to the drag?
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