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Originally Posted by Frank Lee
I can't make a ram-air inlet to fuel my compressed air car? Dang it  |
You could build yourself a ramjet...
Quote:
Originally Posted by Otto
All of the roads that I drive on are static.
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Wrong frame of reference.
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Air trapped under the car will try and escape, but the rougher the underbody is, the more obstructions there are, and more circuitous route to escape.
Reduce the amount of air trapped under the car and/or smooth the path that such air must take. In other words, make it as effortless as possible on the air molecules.
The less disturbance of the air, and/or straighter path that it takes from front to back, the less drag and greater efficiency.
See MacReady et al.
It would be interesting to do tuft tests on a roadway surface, and videotape them as the car drove over at ~70 mph.
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I'm referring to ride height, not underbody smoothness. You posted an analogy of biplane wings that was the focus of my response. In your analogy, the lower wing would have to be moving at a speed equal to freestream velocity relative to the top wing for it to be comparable to a road surface.
The car underbody and road surface are not moving at the same speed, therefore any reference to conventional ducts cannot be applied. I argue that interference drag between the car underbody and road surface does not exist as you imply.
Maybe interference drag does exist, but I can't work out two boundary layers touching each other in this situation. If anyone could clarify, that would help.
- LostCause