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-   -   Stall capture on 3 element airfoil: what turb model? (http://www.cfd-online.com/Forums/openfoam-solving/97626-stall-capture-3-element-airfoil-what-turb-model.html)

Verfblikje February 21, 2012 11:44

Stall capture on 3 element airfoil: what turb model?
 
Dear fellow forummembers,

As the title states, I am trying to capture stall on a three-element airfoil. It is a general aviation airfoil with a double slotted flap.

Using the Spalart-Allmaras model I am not able to get a reasonable result. C_L values hover around 0.02 and drag is in the region of 2E-22. I have been trying to get a reasonable result for some while now, but no luck.

Then, I have also tried k-omega SST. Even at 8 degrees angle of attack (35 degrees flap setting), the airfoil stalls. Even though I am not sure what the stall angle of attack should be, I assume it will be higher than 8. I have yet to try lower angles. I used the wiki article to give me boundary conditions. I have tried the standard settings from the motorBike tutorial and tried some other boundary conditions.

The flow seems to trip at the leading edge of the main element.
Some further information about the case:
Re = 1.5 * 10^6
U = 18 m/s
chord = 1.25 m

Could you give me some tips for improving my results?

Thanks in advance,

Nick

P.S. I am running OpenFOAM 2.1.0

Maff March 26, 2012 12:39

I'm having similar problems.

I just tried the airFoil2D tutorial (OpenFOAM 2.1.0), but with kOmegaSST model.
The detachment occurs too soon, at the leading edge.
With SpalartAllmaras and kOmega models, the detachment occurs at the very end of the trailing edge.
What can cause this discrepancy?
Is this related to omegaWallFunction?
Why is it affecting more the kOmegaSST model than the kOmega model?

DLuo May 15, 2014 16:05

I'd recommend this NASA page. Rather than jump straight to a 3 element high lift airfoil, start small and see if you can get one of these grids to correlate with the literature.

http://turbmodels.larc.nasa.gov/naca0012_val.html


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