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-   -   Non converging simulation (http://www.cfd-online.com/Forums/fluent/71267-non-converging-simulation.html)

ghost December 22, 2009 11:15

Non converging simulation
 
Hi, I have setup a 2D flow over an aerofoil, with some blowing along the top leading edge.

I ran the test using the k-e model, steady state, courant number 0.5.

After 200000 iterations, fluent still does not show that it has converged. The residuals are fluctuating about a mean value, with the continuity decreasing at a very slow rate. It is still at order of e-3.

A plot of the lift and drag coefficient shows that they are increasing at a very slow rate, almost flat from the the zoom out view.

Can I assume that the values have converged, since I am only interested in getting the lift and drag coefficient values? Or is there any method that I can do to speed up the converging?

Thank you.

teguhtf January 1, 2010 23:27

you can repair your meshing. maybe there is bad quality. make your meshing near wall is smooth. because it'll take effect on your simulation.
hope it helps!!

ghost January 4, 2010 22:05

Quote:

Originally Posted by teguhtf (Post 241265)
you can repair your meshing. maybe there is bad quality. make your meshing near wall is smooth. because it'll take effect on your simulation.
hope it helps!!

may i know how can i make the near wall meshing smooth?

usually i just mesh the face and check that the cells are not too skewed.

JaC January 5, 2010 10:25

Hi,

if you use Gambit, you can do the boundary layer in the meshing tab - I thin its the first button. And if you use ansys mesher use the Inflation function.

Regards

Jakub B.

ghost January 5, 2010 10:31

i have always used the boundary tab on the near wall surface for all my simulations.

JaC January 5, 2010 10:40

Hi again,

in that case you can try to refine your mesh...if the problem persists you can rule out bad geometry as cause of your issue and check other things that may have caused it...

Maybe you could upload the picture of your mesh...

Regards

Jakub B.

ghost January 5, 2010 11:00

http://i48.tinypic.com/27xo6zp.jpg

here is a pic of the mesh at the injection area.

if someone is willing to help, i can send u the mesh file.

thx


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