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Old 06-26-2019, 12:32 PM   #47 (permalink)
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Originally Posted by Vman455 View Post
The airspeed and belt speed are the same; there is no acceleration of air by the belt, and no boundary layer forms between the belt and flow. This is what happens to a car on the road; to accurately represent that, you must have one boundary layer under the car, between the car underbody and the airflow. A second boundary layer between the ground and flow results in a u-shaped velocity gradient.

Elevating a car in a wind tunnel is a common practice for correcting for both wheel drag when using stationary wheels and floor boundary layer when using a fixed floor.
At the front of the belt, the boundary layer of air IS stationary - so the moving belt would accelerate it.

If there was a streamlined plate that had a moving belt, was raised up and was in contact with the wheels, then that might improve the "accuracy" without additional measures to try to correctly mimic a rolling car on a road?
Sincerely, Neil
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