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Old 07-30-2013, 04:54 PM   #40 (permalink)
aerohead
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paths

Quote:
Originally Posted by ennored View Post
Guy I used to work with always said "If you were an air molecule..."

So, if you were an air molecule headed straight at the front of the three shapes, where would you like to go?

The left body is easy, any path around it is the same. The ones to the right are different. Superimposing a clock face, the 12, 3, 6, and 9 o'clock paths are the same simple paths from the left body. Anything but those paths is a longer path. And the war is lost...
Hucho 'said' that where we get into trouble with the square edges is that as the high pressure under the vehicle will try to seek equilibrium with the lowest pressure up on top.
As the two airstreams collide at differing velocities,they'll whip up into attached vortices on the corners,as rising moist super-cell Gulf air over Colorado would collide with the jetstream overhead,initiating the vorticity that will spawn tornadoes as the vortex rolls eastward eventually rotating into the vertical super-vortex over Kansas.
With any body section closer to a body of revolution,as you say,the pathways are more similar,and so to too with velocities.
With sharp lower edges,and even running boards on a pickup,it's harder for the high pressure underneath to even telegraph itself up onto the sides of the vehicle.
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