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Old 02-25-2011, 01:41 PM   #138 (permalink)
3-Wheeler
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Quote:
Originally Posted by NeilBlanchard View Post
Hmmm, I missed that part of the discussion, I guess. It is odd to think that the air is "bumped" out of the way and has a spring affect? One would think that a given volume moves out of the way a given distance, and then moves back.
At rest, the air exerts a pressure of 15 psi on our bodies as we walk through the air. This being at sea-level.

As we walk through the air, the air molecules are "displaced" by the presence of our bodies and move out of the way as we walk.

If one had a sensitive enough pressure instrument, you could measure the pressure rise of the air impacting the front of our bodies as we walk down a hallway for example. There is a slight but perceptible increase in air pressure as we walk. You can feel this pressure change if someone else walks by you will you are standing still.

Quote:
Originally Posted by NeilBlanchard View Post
There must be a repelling force between the molecules in the air that is acting as a spring. So, it is not just the static volume of air that gets displaced, but rather the speed and shape of the front that has a lot to do with it.
You can think of the air itself as a series of molecules that are all attached to each other via small springs, as a lattice structure. Picture yourself standing on the outside of this structure and pushing on the molecules at the edge. All the other surrounding molecules and springs will move in response to your input. The result of this will be a pressure wave that propagates across the entire lattice structure in an attempt to dissipate the pressure you put at the edge.

When your car body moves through the air, the same thing is happening with the displaced air molecules by your car moving them aside. The result of this movement creates a pressure increase in the local air molecules, and this pressure increase attempts to move the molecules back to their original position, but has to wait until your car body passes through that area.

The drawback to this whole scenario, is that once the molecules are moved apart and under localized pressure, they have to be "placed" back in their original position slowly over time to minimize energy losses. This comes in the form of turbulent flow and creates high energy losses. And this is where a streamlined shape like Aeroheads Template comes into play.

The shape of the Template in the tail area, "eases" the air molecules slowly back into their original position as best as possible, with minimal energy losses. In a perfect world, there would only be skin losses due to the shape moving through the air and no turbulent air losses. A trip to the airport to look at wings and air fuselages puts this whole exercise into reality.

Jim.

Last edited by 3-Wheeler; 02-26-2011 at 11:02 AM..
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