CFD Online Discussion Forums - Beam deflection UDF in 2D

Hi,

I am trying to apply the udf found in the manual for beam deflections in 2D

Code:

/**********************************************************

   node motion based on simple beam deflection equation

   compiled UDF

 **********************************************************/

 #include "udf.h"

 

 DEFINE_GRID_MOTION(beam,domain,dt,time,dtime)

 {

    Thread *tf = DT_THREAD(dt);

    face_t f;

    Node *v;

    real NV_VEC(omega), NV_VEC(axis), NV_VEC(dx);

    real NV_VEC(origin), NV_VEC(rvec);

    real sign;

    int n;

    /* set deforming flag on adjacent cell zone */

    SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));

    sign = -5.0 * sin (26.178 * time);

    Message ("time = %f, omega = %f\n", time, sign);

    NV_S(omega, =, 0.0);

    NV_D(axis, =, 0.0, 1.0, 0.0);

    NV_D(origin, =, 0.0, 0.0, 0.152);

    begin_f_loop(f,tf)

    {

       f_node_loop(f,tf,n)

       {

        v = F_NODE(f,tf,n);

        /* update node if x position is greater than 0.02    

        and that the current node has not been previously

        visited when looping through previous faces */

        if (NODE_X(v) > 0.020 && NODE_POS_NEED_UPDATE (v))

        {

         /* indicate that node position has been update

         so that it’s not updated more than once */

         NODE_POS_UPDATED(v);

         omega[1] = sign * pow (NODE_X(v)/0.230, 0.5);

         NV_VV(rvec, =, NODE_COORD(v), -, origin);

         NV_CROSS(dx, omega, rvec);

         NV_S(dx, *=, dtime);

         NV_V(NODE_COORD(v), +=, dx);

        }

     }

  }

  end_f_loop(f,tf);

 }

The problem is that the dx is always evaluated as 0 , I tried the code for a 3d case and it gave large random deformations even though I adapted the values .
Attached is the example I am trying to run.

Does anyone know how to solve this ?

thank you !