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Old   April 13, 2004, 05:57
Default Lift prediction in turbulent models
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I am having serious thoughts about the lift calculation using a turbulence model. I am working with a NACA0015 profile that has a lift coefficient of about 0.06 at an angle of attack of 3 degrees. The model I use is Spalart Allmaras. Can anybody tell me something about the reliability of the calculated lift and drag forces using this model?
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Old   April 13, 2004, 09:22
Default Re: Lift prediction in turbulent models
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As far as I know, SA model is good when there is adverse pressure gradient in the calculation.

I have been working on 2d airfoil (eg NASA LS(1)-0417, some Clark Y etc) analysis for the past two months, and based on my experience, lift is really good (a few % off) but Drag goes to "hell". There are lots of issues why your drag doesn't match up well enough, could be y+ problem, domain size, etc. Have you conducted analysis at high alpha also or currently just the 3 degree alpha case.

Can you be more specific about what you have done (during the problem setup) and what types of results you obtained that you think is not good enough!

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Old   April 13, 2004, 09:49
Default Re: Lift prediction in turbulent models
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Thanks for all the trouble, but the problem has already been solved. The lift coefficient (3d calculation, Y+ was good) was lower because the aspect ratio of the wing is relatively small (1.3). Also the reference area is redefined leaving a satisfyable value for Cl. Thanks for the help!
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Old   April 14, 2004, 01:15
Default Re: Lift prediction in turbulent models
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Quick question,

With the three-d model, how are you rotating the 3d profile of the blade. Im using a NACA012, but, they are ducted and due to close clearances meshing is very tough.

Are you guys using sliding meshes?
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