Quote:
Originally Posted by tasdrouille
Basically, what you'll get putting a 1:18 scale model in a wind tunnel with 60 mph airspeed will not scale properly for a full size model at 60 mph airspeed.
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Or even a 1:18 model at (60/18) mph.
You may enjoy reading the first sentence here:
Reynolds number - Wikipedia, the free encyclopedia
and this one: "[Reynolds Numbers] are also used to characterize different flow regimes, such as laminar or turbulent flow: laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion, while turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce random eddies, vortices and other flow instabilities."
The full-sized car might have turbulent flow where the model has laminar flow, etc. The flows will probably have different shapes, despite the model having the same shape as the full-sized car.
But if you test your scale model in a medium with the same Re, the flows are guaranteed to be equivalent.