# DEFINE_CG_MOTION for flapping wing UDF

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 December 14, 2011, 10:15 DEFINE_CG_MOTION for flapping wing UDF #1 New Member   xyzch001 Join Date: Dec 2011 Posts: 10 Rep Power: 7 Sponsored Links Hi everybody! I'm a graduate student of mechanical engineering working at a Fluent project for my thesys. I have to write a UDF in order to give a motion law to a flapping wing. By using the UDF "DEFINE_CG_MOTION" I need to specify an angular velocity d(theta)/dt so that the oscillation angle of the flapping wing is: theta(t)=25*sin(2*pi*frequency*t+arcsin(3/5))-15 If I use the derivate d(theta)/dt=50*frequency*pi*cos(2*pi*frequency*t+arcsin(3/5)) I lose the constant "-15" so that the oscillation angle is no more from +10 deg to -40 deg. As a matter of fact the positive peak amplitude must be +10 deg and the negative one must be -40 deg. How can I solve the problem? Thank you so much!

 Tags ansys fluent, define_cg_motion, flapping wing, udf

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