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Lift Coefficient Oscillates

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Old   January 10, 2012, 15:31
Default Lift Coefficient Oscillates
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Ming Cai
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Dear Friends

I'm running simulation on a NACA 64 210 airfoil with k-omega sst model with Re = 2.6 E6 . The chord length is 1m.

Angle of Attack ranges from 0 to 20.

everything is fine before angle of attack getting to 12, both lift coefficient and drag coefficients oscillates periodicly after 12 aoa.

I don't know if this is the correct solution. However, before this angle the results are reasonable
Thanks for your help.






Last edited by mingersai; January 11, 2012 at 13:35.
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Old   January 11, 2012, 13:36
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Can anyone tell me how to deal with this?
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Old   January 11, 2012, 14:59
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I would guess that the airfoil is stalling and this oscillation comes from the separation and reattachment of the airflow over the airfoil.
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Old   January 11, 2012, 15:26
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Quote:
Originally Posted by Rhyno466 View Post
I would guess that the airfoil is stalling and this oscillation comes from the separation and reattachment of the airflow over the airfoil.
Hi, Rhyno466

Thanks for your reply. I'm comparing my results with experimental ones. The experimental people pick only one value for this angle of attack. I'm not sure how they did that if the airfoil is stalling.

I have no experience in wind tunnel tests...
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Old   January 12, 2012, 12:01
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May I ask why you are running a transient case instead of just a steady case?
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Old   January 12, 2012, 12:45
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Quote:
Originally Posted by Rhyno466 View Post
May I ask why you are running a transient case instead of just a steady case?
Yep, I'm running transient solution with time step size 0.0001.
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Old   January 12, 2012, 14:49
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Could it be caused by vortex shedding?
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