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Problem in cd of oscillating airfoil at high freq.

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Old   November 27, 2006, 03:31
Default Problem in cd of oscillating airfoil at high freq.
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CH
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hi,

I managed to obtain results of cl/cd of an oscillating airfoil using fluent udf define_cg_motion. at frequency f=1, i managed to get a sinusodial graph for both cl and cd. They are quite close to the published results. dt=0.001

however, when i change f to 2 and rerun, i can get a sinusodial graph for cl (similar to published one) but the graph for cd is oscillating irregularly. i tried to reduce the time down to as small as dt=0.00025 but the result is still irregular.

i can't figure out what's wrong since i only changed the f from 1 to 2.

can someone help?

thanks alot!
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