Quote:
Originally Posted by 3-Wheeler
Hi Aerohead,
I'm not sure that I completely agree with what you said about "pressure" being the only factor in air movement.
Air molecules *do* have mass and because of that also have inertia.
Now the air molecule's mass is very low, but it's still there.
Regarding moving an object through the air, the biggest factor is pressure itself and the fact that the molecules "communicate" with each other at only the speed of sound, and not faster like electrons do in electrical circuits.
Air moving close to the speed of sound becomes a major issue because as you know, the "communication link" between molecules is almost nil due to the high speed. The air molecules can not communicate their localized pressure to surrounding molecules, because they are all moving at the speed of sound, and this is as fast as the pressure pulse in the air can move.
Obviously your Streamlining Template is designed to give the air time to move back into it's originally undisturbed space before our vehicle passes through, via the localized air pressure at the time. And this is partly due to particle mass, local pressure, and the speed of sound, all contributing to the general movement of air back to it's original state.
Jim.
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It's not just the mass either though. Moving air takes energy, because air is surrounded by air. Pushing air out of the way of a vehicle means shoving air molecules into other air molecules. It takes energy just like moving air with a fan takes energy.
A more gradual transition is good in the same way a shallower raked windshield is good-- air is moved more slowly relative to the speed of the vehicle.
Look at your vehicle's electric cooling fan. See how the blades are curved? Why don't they just use the flow departure angle for the whole blade and make it flat?
Because it takes less energy to ramp up their air speed gradually over the blade surface, from a shallow angle to a steep angle.
We need to put to rest this nonsense about attached flow being the end all be all except at supersonic speed. A normal fan doesn't spin at supersonic speed.
