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April 14, 2010, 14:04 |
naca 0012 validation case: wrong Cd
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#1 |
Senior Member
Join Date: Feb 2010
Posts: 213
Rep Power: 17 |
Since I was simulating an external flow on a blade section of a marine propeller and lift and drag coefficients seem to be good (I checked them with Xfoil), I thought to test a NACA 0012 airfoil. Setting are:
= 2E+6 = 1 ° According to experimental results, I obtain a good =0.11 and a bad =0.011 (vs 0.0064). I guess it depends on my fully turbulent models ( and Spalart-Allmaras), because my coefficients are similar to Xfoil ones (if I force transition at on both surfaces). But I guess if I can improve my settings (BC, fvSchemes, fvSolution): any suggestions? Meanwhile I'll go on with different angles of attack. |
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September 28, 2010, 10:45 |
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#2 |
Member
Marta Lazzarin
Join Date: Jun 2009
Location: Italy
Posts: 71
Rep Power: 17 |
Dear Vaina, have you found out something concerning the comparison between the Cl and Cd calculated by OFoam and those coming from experiments?
I am simulating the flow around a Naca airfoil too, but the final results are not as good as those of other CFD codes, even if the simulation has converged (residuals lower than 1e-6). Moreover, i had to choose the Spalart-Allmaras equation for turbulence modelling, because with k-epsilon model i didn't succeed in completing the run. Have you obtained something interesting or useful out of your trials? Thank you very much, Marta |
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September 28, 2010, 12:36 |
Cd
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#3 |
New Member
Christiano Santim
Join Date: Sep 2009
Posts: 11
Rep Power: 17 |
Quote:
Attention to its trailing edge. You need to trick the fluent little refining this site. Using k-omega sst results are good. If u want, i have some results.
__________________
C Santim Chemical engineer chrisoff22@yahoo.com.br |
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September 28, 2010, 12:37 |
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#4 |
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Simon Lapointe
Join Date: May 2009
Location: Québec, Qc, Canada
Posts: 33
Rep Power: 17 |
It is normal that the drag coefficient computed with turbulent RANS models (as Spalart-Allmaras) be higher than the experimental or XFOIL values since the models predict a fully turbulent boundary layer but in reality there is an important region of laminar boundary layer. If you want a better prediction of Cd in general CFD codes, you'll have to use transitional RANS models.
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October 22, 2010, 04:40 |
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#5 |
New Member
anonymous
Join Date: Oct 2010
Posts: 1
Rep Power: 0 |
Hi can I know what source of validations you all use? Can you send the database to me please?
fung_wern@hotmail.com Thank you! |
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July 15, 2011, 12:50 |
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#6 | |
Senior Member
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Hello Vaina,
DO you have your case available for download? I am interested in both system and constant folders, including mesh. You mentioned: Quote:
Regards, Guilherme |
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