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-   -   Multi-Body Airfoil simulation problems (http://www.cfd-online.com/Forums/openfoam-solving/68130-multi-body-airfoil-simulation-problems.html)

ivan_cozza September 8, 2009 04:58

Multi-Body Airfoil simulation problems
 
1 Attachment(s)
Hi Foamers,
I'm trying to simulate the flow around a 2D high lift configuration airfoil (slat - main - flap), Re=6x10^6, Ma=0.2, AoA = 12.2, with simpleFoam, k-Omega SST turbulence. I tryied both high Re mesh type, so yPlusMin > 30, and Low Re mesh type, so yPlusMax < 1, as in OF 1.6 it's possible to switch off the wall-functions in SSt model.

My boundary condition are:

Far field:
U - inletOutlet
p - inletOutlet
k - turbulentIntensityKineticEnergyInlet
Omega - turbulentMixingLengthFrequencyInlet

Walls with yPlus > 30
U - fixedValue (0 0 0)
p - zeroGradient
k - kqRWallFunction
Omega - omegaWallFunction

Walls with yPlus < 1
U - fixedValue (0 0 0)
p - zeroGradient
k - fixedValue 0
Omega - omegaWallFunction

I used the standard best-practise to get the solution, so starting with upwind schemes at the beginning and then 2 order Gamma schemes, playing with the relaxation factors to make it converge, and I get a stable solution. My fvSchemes and fvSolution are attached.

The results are like this:

U


P

http://img40.imageshack.us/img40/3478/12574101.png

k

http://img40.imageshack.us/img40/5881/38715448.png

cp

http://img5.imageshack.us/img5/4703/72737271.png

The cp values are completely incorrect, as the reference solution for this case has a negative peak of around -4 near the main, and a cp of about -2 / -2.5 on the main upper surface.
Does anyone have some idea to get better results? I'm struggling on it from weeks...
Have a nice day!

luca_g September 11, 2009 10:18

Dear Ivan,

I couldn't see the Cp plot so don't really know how far you are, still I couldn't find anything obviously wrong in your fvSchemes and fvSolution files.

If you agree, I would be interested in trying computing this case (I was looking for multi -airfoil test cases) and share with you the results if you could give me the geometry (best would be your own grid and the full OF case, but would be nice to have the airfoil coordinates so that I could optionally generate a new mesh as well).
To be fair, I would ask you a reference to the experimental results only after having done the computations..

Ciao,

Luca

squadron September 17, 2009 05:38

Your pressure is ~3 times atmospheric...


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