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-   -   2D airfoil at 15deg (http://www.cfd-online.com/Forums/fluent/95988-2d-airfoil-15deg.html)

pisanopisalo January 9, 2012 16:28

2D airfoil at 15deg
 
1 Attachment(s)
I have tried the tutorial of a naca0012 airfoil which is done with a C-grid, 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?

shk12345 January 9, 2012 23:58

Just low value of under relazation factor and try to use different schemes.

pisanopisalo January 10, 2012 03:18

Quote:

Originally Posted by shk12345 (Post 338561)
Just low value of under relazation factor and try to use different schemes.

thank you for your reply, I'm a total newbie to fluent, could you please try to explain to me what schemes to use?
Thank you!

shk12345 January 10, 2012 11:39

there are several schemes like
24.2.1 First-Order Upwind Scheme
24.2.2 Power-Law Scheme
24.2.3 Second-Order 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

pisanopisalo January 10, 2012 12:45

I had it set at Second-Order Upwind.

First-Order 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 power-law scheme, or quick scheme?

shk12345 January 10, 2012 12:47

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.

level January 13, 2012 12:05

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.cfd-online.com/Forums/flu...-possible.html

shk12345 January 14, 2012 05:38

Quote:

Originally Posted by level (Post 339203)
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.cfd-online.com/Forums/flu...-possible.html

It is giving you solution but not a stable solution . And to match your results with any real value your solution should be stable.
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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