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January 9, 2012, 16:28 
2D airfoil at 15deg

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I have tried the tutorial of a naca0012 airfoil which is done with a Cgrid, and at a 6deg angle.
Here is the link to the toutorial: https://confluence.cornell.edu/displ...oil++Geometry I have tried it an it works fine, but then I just changed the x and y velocitys so the airfoil is at a 15deg angle, with all the other settings the same, I run the calculation and it does not give out a result. See attached picture. Does anyone have any idea why is this or how to correct it? Maybe something not right in the setup? Last edited by pisanopisalo; January 9, 2012 at 17:15. 

January 9, 2012, 23:58 

#2 
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shoeb khan
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Just low value of under relazation factor and try to use different schemes.


January 10, 2012, 03:18 

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January 10, 2012, 11:39 

#4 
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shoeb khan
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there are several schemes like
24.2.1 FirstOrder Upwind Scheme 24.2.2 PowerLaw Scheme 24.2.3 SecondOrder Upwind Scheme 24.2.4 QUICK Scheme see this page for more detail http://jullio.pe.kr/fluent6.1/help/html/ug/node814.htm just google more for more results shk 

January 10, 2012, 12:45 

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I had it set at SecondOrder Upwind.
FirstOrder Upwind Scheme gave me unreal results. The lif coefficient was 1.3 for the 15 deg angle, but at 10deg it was 2.1(with second order upwind) And there are only these two schemes available, where can i find the powerlaw scheme, or quick scheme? 

January 10, 2012, 12:47 

#6 
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shoeb khan
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Try to use the Pressure velocity coupling as : coupled, solver and first order scheme it best faster convergence
then once the solution is conveged switch to second order and get the results. 

January 13, 2012, 12:05 

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There could also be stall at such high angle of attacks which produce such a behaviour... What do you mean with "it does not give out a result"? No convergence?
I have a similar problem and i also dont know what to do now... http://www.cfdonline.com/Forums/flu...possible.html 

January 14, 2012, 05:38 

#8  
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shoeb khan
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Quote:
Sometimes a oscillation convergence is also accepted like in your case.But it will be better if you can try to get a stable solution shk 

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