[edems86]

Hello, I am using fluent to simulate a rising bubble in a column of water. The bubble is an oil bubble and the simulations are made in 2D axisym.

I would like to get the terminal velocity of the bubble and have decided to use a UDF to get the center of mass of the bubble. However this is my first UDF and the results I get is always 0 and I do not know where the problem comes from. I hope somebody will be able to help me out here. Thank you very much

The udf I wrote :

#include "udf.h"
#include <math.h>


DEFINE_EXECUTE_AT_END(execute_at_end)
{  
  int phase_domain_index;

  Domain *subdomain;

  Domain *mixture_domain;
  mixture_domain = Get_Domain(1);

  double num;
  num = 0.0;

  double denom;
  denom = 0.0;

  double bar;

  double vol;
  vol = 6.25e-8;

  double rho;
  rho = 974.5;
  
  #if !RP_HOST

  FILE *file = fopen("data.txt", "a");
  if(!file)
    {
        Message("Cannot open the file");
    }
  else
    {
    /*loop over all subdomain(phases) in the superdomain(mixture)*/
    sub_domain_loop(subdomain, mixture_domain, phase_domain_index)
        {
	    Thread *cell_thread;
	    cell_t cell;
	    real xc[ND_ND];
         /*loop over all cell threads in the domain*/
	    thread_loop_c(cell_thread, subdomain)
	        {
		    /*loop over all cells in the thread*/
		    begin_c_loop_all(cell, cell_thread)
		        {
		    	/*get the cell centroid*/
			    C_CENTROID(xc, cell, cell_thread);

                            num = num + C_VOF(cell, cell_thread)*xc[0]*rho*vol;
                            denom = denom + C_VOF(cell, cell_thread)*rho*vol;
		        }
		    end_c_loop_all(cell, cell_thread)
            }
        }
    }
    bar = num/denom;
    fprintf(file,"Resultats: %g\n",bar);
    fclose(file);
    #endif
}