[Rabeyia Manzoor Illahi]

I have to make a udf of the following two equations but unable to get the movement for omega, if you can please help.

#include "udf.h"
DEFINE_CG_MOTION(air,dt,vel,omega,time,dtime)
{
Thread *t;
face_t f;
real tau,delTau,Tau1, pi, U, c, Taur;
pi = 3.14159265;
U=1;
c=1;

/*time=time+dtime;*/

tau=(time*U)/c;
delTau = (dtime*U)/c; /*(dtime*U)/c*/;
Tau1= (time*U)/c;/*(time1*U)/c*/;
Taur= Tau1-delTau;


vel[0] = 0.5*(1+cos(pi*(tau-Tau1)/delTau));
omega[2] = 77.5*(1-cos(2*pi*(tau-Taur)/delTau));



}

[AlexanderZ]

cos(2*pi) = 1

so omega[2] = 77.5*(1- 1) = 0 always

modify your equation

[Rabeyia Manzoor Illahi]

Sir thankyou so much for thr reply. But the cos function also involves other terms so it wont be zero.
And I have take these equations from a paper of "Unsteady aerodynamic force generation by a model fruit fly wing in flapping
motion" by Sun and Tang.
If you can please help.

[AlexanderZ]

put

tau=(time*U)/c;
delTau = (dtime*U)/c; /*(dtime*U)/c*/;
Tau1= (time*U)/c;/*(time1*U)/c*/;
Taur= Tau1-delTau;

in

 omega[2] = 77.5*(1-cos(2*pi*(tau-Taur)/delTau));

[Rabeyia Manzoor Illahi]

Sir if I run the omega equation alone, its working but both velocity and omega not working together. If you can please help.

[AlexanderZ]

how it could works if omega[2] = 0 ????
check the difference between codes


did you compile UDF? this is must for DEFINE_CG_MOTION macro

for more informaton about dynamic mesh you may check Ansys Fluent Customization manual -> Dynamic Mesh DEFINE Macros chapter