# No motion with CG_MOTION

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 June 4, 2012, 07:04 No motion with CG_MOTION #1 New Member   Join Date: Apr 2012 Posts: 17 Rep Power: 7 Hello every one... I have a problem with using of dynamic mesh... I'm just trying to apply udf provided by fluent manual to the wall of a particle in a tube fluid flow. The udf is the following: * 1-degree of freedom equation of motion (y-direction) * compiled UDF ************************************************** **********/ #include "udf.h" static real v_prev = 0.0; DEFINE_CG_MOTION(particle,dt,vel,omega,time,dtime) { Thread *t; face_t f; real NV_VEC(A); real force, dv; /* reset velocities */ NV_S(vel, =, 0.0); NV_S(omega, =, 0.0); if (!Data_Valid_P()) return; /* get the thread pointer for which this motion is defined */ t = DT_THREAD(dt); /* compute pressure force on body by looping through all faces */ force = 0.0; begin_f_loop(f,t) { F_AREA(A,f,t); force += F_P(f,t) * NV_MAG(A); } end_f_loop(f,t) /* compute change in velocity, i.e., dv = F * dt / mass velocity update using explicit Euler formula */ dv = dtime * force / 0.032986723; v_prev += dv; Message ("time = %f, x_vel = %f, force = %f\n", time, v_prev, force); /* set x-component of velocity */ vel[1] = v_prev; } I have only defined the wall of particle as rigid body, and, in the motion attribute I have chosen the udf library. obviously the simulation is in transient time. It's a very simple problem...but my particle doesn't move!!! Why??? Should I define a moving zone surrounding the particle? Should I define any kind of contact regions between particle and fluid? Could anyone help me?

 June 20, 2012, 12:10 #2 New Member   Kyle Join Date: Jun 2012 Posts: 12 Rep Power: 7 did you ever figure this out? because I'm having the exact same problem. I even copied the same UDF as you.

 June 21, 2012, 16:00 #3 New Member   Join Date: Apr 2012 Posts: 17 Rep Power: 7 No, I'didn't. I'm using 6DOF solver...

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