[cuan1029]

Greetings,

I tried to simulate synthetic jet and wanted to study the flow velocity and heat transfer of it.

However, I'm stuck with the UDF for the oscillating membrane.
I have go through one of the UDF tutorial,Using a UDF to Control the Dynamic Mesh of a Flexible Oscillating Membrane, which related to my topic.

For my case, I do not have the rotating butterfly but only the oscillating membrane which located at the bottom of the geometry

Attachment for my geometry



I tried to use the grid motion part in the UDF and do some minor modification according to my case, but I am not fully understand the UDF provided in the tutorial which causing me hard time.

The following is my UDF:

#include "udf.h"

#define  omega      1           /* rotational speed, rad/sec        */
#define  R          0.375        	/* radius of the arc, meters        */

DEFINE_GRID_MOTION(moving_arc, domain, dt, time, dtime)
{
  Thread *tf = DT_THREAD (dt);
  face_t f;
  Node *node_p;
  real alpha, theta, x, ymag, yfull, y;
  int n;
  
/* Set/activate the deforming flag on adjacent cell zone, which       */
/* means that the cells adjacent to the deforming wall will also be  */
/* deformed, in order to avoid skewness.                                   */
  SET_DEFORMING_THREAD_FLAG (THREAD_T0 (tf));

/* Compute the angles:                                               */
  alpha = omega * CURRENT_TIME;
  theta = 2.0 * alpha + 3.0 * M_PI / 2.0;
  
/* Loop over the deforming boundary zone's faces;                         */
/* inner loop loops over all nodes of a given face;                           */
/* Thus, since one node can belong to several faces, one must guard  */
/* against operating on a given node more than once:                       */

  begin_f_loop (f, tf)
    {
      f_node_loop (f, tf, n)
        {
          node_p = F_NODE (f, tf, n);

          /* Update the current node only if it has not been         */
		  /* previously visited:                                     */
          if (NODE_POS_NEED_UPDATE (node_p))
            {
              /* Set flag to indicate that the current node's        */
			  /* position has been updated, so that it will not be   */
              /* updated during a future pass through the loop:      */
              NODE_POS_UPDATED (node_p);

			  x     = NODE_X (node_p);
			  ymag  = sqrt (R*R - x*x) + 0.03;
			  yfull = ymag - 0.1;
			  y     = yfull * sin(theta);
			  NODE_Y (node_p) = y;
            }
        }
    }
  end_f_loop (f, tf);
}

Here is what I get after I previewed the dynamic motion in Fluent


In my case, do I have to use "theta" as written in the UDF above?
How to apply the UDF in tutorial for my case?

Thank you in advance for any help and advice.