CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   FLUENT (https://www.cfd-online.com/Forums/fluent/)
-   -   Problem in cd of oscillating airfoil at high freq. (https://www.cfd-online.com/Forums/fluent/42945-problem-cd-oscillating-airfoil-high-freq.html)

CH November 27, 2006 03:31

Problem in cd of oscillating airfoil at high freq.
 
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!


All times are GMT -4. The time now is 21:54.