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  Posted by: carldelo on Sep-22-12 11:56 AM (EST)
 

-- Last Updated: Sep-22-12 5:22 PM EST --

Re: the egg, you are correct, in the same way that on a baseball or the nose of a jet, there is a single stagnation point at the front of the body.

On the wing of the jet, however, there will be a stagnation line down the leading edge, and another pinned to the trailing edge (the Kutta condition, as you mentioned). The difference between the two situations is obviously the aspect ratio of the body as it is presented to the flow (AR = weight/height).

An egg, ball or jet nose have AR of 1, more or less, whereas a wing will have an AR that is greater, at least 3 for it to work as intended, 5 or 10 (or more) leads to increased aerodynamic efficiency.

Anyway, the high AR forces the fluid to pick a side as it flows around the wing - the shape drives the flow. Some flow will sneak around the end of a finite wing, creating the tip vortex, but for the majority of the length, the wing separates the flow into two distinct streams.

An egg presents a fairly uniform obstacle, so the flow is free to move around it on all sides. Flow behind the body depends on its shape - an egg or baseball will have a wide wake zone, generally turbulent (bluff-body wake), a streamlined jet will have a stagnation point at the end somewhere.

A GP is a high AR body, so I was thinking of that when I misspoke in my previous post. I said 'there is no stagnation point in 3D flow' and should have finished with 'around a high aspect ratio body' to make it a correct statement.

PS a ridge anchors the stagnation line, but does not necessary make the flow symmetrical - a canted blade will not have symmetrical flow. A wandering stag. line causes flutter via pressure fluctuations; the ridge stops the wandering.


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