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Old 06-24-2019, 06:35 PM   #42 (permalink)
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Originally Posted by NeilBlanchard View Post
Interesting discussion - I would think the slot just ahead of the moving "roadway" belt would be supplying air to make the relative motion of the roadway and the boundary layer of air be stationary relative to each other.

With the "extra" air flow introduced at the front of the belt - the belt's motion would possible accelerated the already moving air. By the way, what affect would the texture of the belt / roadway have on things?

By vacuuming some air away from in front of the belt would seem to INCREASE the motion of the air relative to the moving belt, and thereby make the effect of the moving belt, and therefore lowering air pressure under the car - which makes it LESS "realistic"; not more.
Don't forget: at these speeds, there is a no-slip condition between the airflow and any wall or body surface; so, with a stationary floor, there's already a pretty thick boundary layer (which thickness is proportional to the root of the distance the flow has traveled along the wall) by the time you get to where the car is (and the moving ground/belt begins). In a real car moving along a road, there is no boundary layer between the air and road since they are both stationary. To replicate this in a tunnel, you have to suck that boundary layer away by sucking the air out with a suction slot, or elevate the vehicle so it's high enough that the boundary layer on the floor doesn't affect it and skew the results.

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