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No motion with CG_MOTION

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Old   June 4, 2012, 07:04
Default No motion with CG_MOTION
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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;
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())
/* 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;
force += F_P(f,t) * NV_MAG(A);
/* 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,
/* 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?
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Old   June 20, 2012, 12:10
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did you ever figure this out? because I'm having the exact same problem. I even copied the same UDF as you.
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Old   June 21, 2012, 16:00
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No, I'didn't.

I'm using 6DOF solver...
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