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#1 |
Senior Member
CFD
Join Date: Nov 2010
Location: United States
Posts: 243
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![]() I have been working on the simpleFoam with the example airfoil2D. I implemented the files that are relevant to kOmega turbulence model into the zero file. I did all required steps in order to get it to work. The case file ran correctly and it gave me similar results to Spalart Allmaras. However, I feel that the drag and left values are a little bit different than the theoretical results. For instance, for angle of attack 2 degree, the CFD lift coefficient result was 0.652044. On the other hand, the theoretical result for the same angle of attack was 0.4865, which gives an error for about ![]() Kind regards, |
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#2 |
New Member
Ahmad Al-Zoubi
Join Date: Nov 2013
Posts: 17
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In general:
- Did you make grid independence study? - What about the boundary conditions? - Did you reach converged solution?... If you are aware about the above facts, then you can blame the 2 equation turbulence model for any inaccurate results. All the best and success. |
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#3 |
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I will provide a picture shows the monitor convergence. However, I don't know a lot about making a grid independence. Could you please explain what do you mean about it.
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#4 |
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As you are aware, from turbulence equations we have the following:
k=(3/2)(Uinf*I)^2 Where Uinf=26 m/s, and I=0.05 for the external flow. Therefore, k= 2.535. Similarly, omega= (0.09*k)/(beta*kinematic viscosity) kinematic viscosity= 10^-6 m2/s, beta =0.1-1 (I chose 0.5) Omega= 182.52. Am I right? Regards, |
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#5 |
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Picture shows the monitor convergence
Last edited by tareqkh; December 9, 2014 at 22:11. |
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#6 |
New Member
Ahmad Al-Zoubi
Join Date: Nov 2013
Posts: 17
Rep Power: 13 ![]() |
Dear tareq,
Thanks for the supplied information. - The provided image shows that there is a trend to convergence. However it doesn't mean that your solution is converged yet... Please check the results after some more hundred iterations and compare them with the previous one. - Did you use the same boundary conditions as in the experimental case. - You are using k-omega turbulence model. It worths also to check the results with realizable k-epsilon or v2f models. - Grid independence study means checking the effect of grid refinement on the results. So make a more fine mesh (taking into account a reasonable y+ value) and compare the results. Do this until you see (engineering) minor difference between the results All the best and success Ahmad |
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