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wing tips in 3D panel codes

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Old   April 6, 2014, 09:49
Default wing tips in 3D panel codes
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Joachim
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Hey everyone,

I am trying to write a 3D panel code based on Dirichlet BC (sources+doublets).
Everything is done, and I am now trying to verify the implementation. I am using a finite NACA0012 wing to do that.

The pressure distribution at the mid-span is fine, but as I get closer to the tips, my pressure becomes a bit funky. Because of that, my lift predicted is slightly too small, and my lift induced drag is way too big (I get cd = K*cl^2, but my k is at least twice the expected value).

I think I am not treating my wing tips correctly. Does anyone know how to do that? Initially, I did not put anything there. Then I added sources+doublets, but it did not change anything.

How are wingtips typically handled in 3D panel codes??

Thank you very much!

Joachim
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Old   April 7, 2014, 16:38
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Joachim
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As I refine my grid at the tips, the Cp decreases to very small values at the trailing edge.

As shown in figure 1, my doublet strength distribution looks pretty cool, but the gradient at the tip goes to infinity as I refine my grid (see figure 2. mu distrib for x= cst just before the trailing edge).

Since my induced velocity is the gradient of mu (doublet strength), the cp predicted becomes very very low.

Would someone know what is going on?? How could I fix this issue at the tips??

Thank you very much!!

Joachim
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