# Problems with simulating an airfoil

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 November 22, 2011, 10:45 Problems with simulating an airfoil #1 New Member   Join Date: Nov 2011 Posts: 2 Rep Power: 0 Hi guys, i have some major problems with simulating a wind turbine. The biggest problem is that i don't get the right torque. I found out that this is due to a wrong calculated lift coefficient. That's why i tried to simulate an easy shaped blade and see if i can get the right coefficient at this one, but i failed too. I am supposed to get a lift coefficient of 0.594 using Naca0012 at wind velocity 20 m/s and an angle of attack of 5 degree. My result is sadly about 0.22. I put my blade (chord: 1m; width 2m) in an ashlar-formed domain (length: 10m; width: 3m; height: 4m) and meshed it with a trimmer getting a approx. 1.7 million cells. My front is a velocity-inlet with 20 m/s, my top, bottom and rear are pressure-outlets and my both sides have the symmetry-boundary-condition. I'm using a steady-state case with segregated flow, constant density and the SST (Menter) K-Omega model (Gamma ReTheta treatment). I read some papers which used the same set up, so I think this should be appropriate. I also read somewhere at this forum that I have to look at my boundary layer. Well, the thickness is 6mm and inhibits 12 layers. My y+ scalar field says that my blade is in the range of 0 to 1.98. The values above 1 are only near the very beginning of my blade and at the sides. I also know that there is a y+ wall distance estimation tool on this webpage. But my english is not my first language and so i totaly don't know what to do with this estimated wall distance (which I think is very important). So, if anyone of you can improve my simulation, I'd be very grateful. Greetings, Flo

 November 22, 2011, 14:17 #2 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 8 gamma re theta is not so easy to use. have you at least tried with the standar k-omega sst? the advantage of the transitional model should be more about the drag. first of all, your domain looks a little bit small. i usually keep at least 30 cordlenght in front and on the top and bottom, and about 60 downstram of the blade to prevent that the imposed b-c infuences the solution. also, i would reccomand checking the inlet turbulent quantities, to see if they are reasonable.