komegaSST model
Hi!
I am new to OpenFOAM and I have to use OpenFOAM for my diploma thesis. I want to compare the results of OpenFOAM with simple examples, which can be calculated by hand. My first example is a straight pipe flow and i already have problems. My geometry is a 1mx1m quadratic tunnel with a length of 20m. I defined all boundary conditions (inlet 5 m/s, outlet pressure=0, wall ). The flow is turbulent and i use the komegaSST model for the turbulence. i simulated the flow with different mesh resolutions (various y+). The y+ values i were 30, 50, 100, 150. Now the problem is that i calculated the pressure loss analytically and the OpenFOAM results aren't even near the exact results. They are 30% (and for high y+ values even more) away from the exact results. Could anybody please help me with my problem? Thanks, Daniel |
Hi,
You should try with y+ = 1 and Wall Functions : - kqRWallFunction for k - omegaWallFunction for omega - nutLowReWallFunction for nut. I think this is the best way to use the komegaSST turbulence model. Regards, |
Quote:
but i have a question. I am really new to OpenFOAM. How do i define Wall Functions? |
In the 0 directory you have files for k, omega and nut. You define the wall functions for your walls in these files. You should read the user guide for more information.
|
Ah ok thank you very much.
But my Re-Number is pretty high (10^5). I don't think that low Re function is correct? |
Actually, when you use a y+ = 1, you use (or at least you should) a Low-Re formulation of the turbulence model. In OF, the difference between Wall functions and the Low-Re formulation is not very clear. You should read this thread for a better understanding :
http://www.cfd-online.com/Forums/ope...-openfoam.html Let me know if your results are better with y+ = 1. |
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