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How to access only one phase in multiphase model by UDF

Hello guys,

I am trying to write an UDF to write data (cell volume, spec diss rate) only for one phase in multiphase (vof) model.
However, either I get all cells or a segmentation violation error.
I tried different methods to access only primary_phase by threads or domains, but I do not have any success.

Could you help me please...
For checking, used a quader with 8000 cells, patched to water in 4000 cells.
I did and didnt run some iterations, nothing helps...

This UDF writes cell volume of all cells, not only primary phase
If I switch C_VOLUME to C_D for spec diss rate, a seg viol error aoccurs.

Code:

#include "udf.h"



DEFINE_ON_DEMAND(write_data)

{

  cell_t c;

  int ID = 2; 

       /* Zone ID for wall-1 zone from Boundary Conditions panel */

  Domain *mixture_domain = Get_Domain(1);

  Domain *subdomain = DOMAIN_SUB_DOMAIN(mixture_domain,0);

  Thread *thread = Lookup_Thread(subdomain, ID);



  FILE *output=fopen ("epsilon.out","w");



  begin_c_loop(c, thread)

     {

        fprintf(output,"\nvof=%e", C_VOLUME(c,thread)); 

     }

  end_c_loop(c, thread)

fclose(output);

}

This UDF writes C_VOF for all cells, not only primary phase
eventhough C_VOF(c,pt[1])

Code:

#include "udf.h"



DEFINE_ON_DEMAND(print_vof)



{

Domain *mix_domain = Get_Domain(1);

Thread *mix_thread;

Thread **pt;



mp_thread_loop_c(mix_thread, mix_domain, pt)

{

cell_t c;

begin_c_loop(c, pt[1])



Message("cell volume fraction = %f\n",C_VOF(c,pt[1]));



end_c_loop(c, pt[1])



}

}

This UDF writes values for all cells too.
Eventhough if(C_VOF(cell,subthread) = 1)

Code:

#include "udf.h"



DEFINE_ON_DEMAND(print_id)

{

Domain *mixture_domain = Get_Domain(1);

Domain *s_d = DOMAIN_SUB_DOMAIN(mixture_domain,0);                /*subdomain pointer, locally defined*/

Thread *mixture_thread;

cell_t cell;



int p_d;                 /* loop counter for phase_domain_index, locally defined*/

int p_d_id;                 /* mix_domain is available*/



FILE *output=fopen ("epsilon.out","w");

fprintf (output, "energy dissipation rate distriubtion\n");

fprintf (output, "epsilon,volume\n");

int phase_domain_index=0;



sub_domain_loop(s_d, mixture_domain, phase_domain_index)

  {

        /* loop over all cell threads in the primary phase domain  */

                    thread_loop_c(mixture_thread,s_d)

                     {

                        /*Thread *st = THREAD_SUB_THREAD(cell_thread, 0);*/

                        /* loop over all cells in primary phase cell threads  */

                               begin_c_loop(cell,mixture_thread)

                        {

                        /*if(C_VOF(cell,mixture_thread) = 1)*/

                        Message("\nDone... %g", C_VOF(cell,mixture_thread));

                        fprintf(output,"\nDone...");

                        }

                        end_c_loop(cell,mixture_thread)

                }

  }        

fclose (output);



}

Eventhough I have 3 examples here, I would like to go to the first one, since I need Lookup_Thread for determining the size of an array to parallelize the udf.
Examplers for parallelizing are here: http://www.fluentusers.com/fluent/do...df/node231.htm
I do not know how I can to this when using a loop over domains or threads, since the size of the array needs to be send from nodes to host...
If I check the udf, it seems very clear to me: I define a domain, then a subdomain, then I define a thread by using subdomain for lookup...
That means, in thread it is supposed to point to thread in subdomian, or better to thread in domain with phase index 0...
However, C_VOLUME can be written, but C_D or C_VOF causes a seg viol error...

Actually, the task seems very easy to me.
Write cell values from cells which are associated with primary phase.
I have tried different methods to access one phase only.
However, I am at one's wit' end...
Any help is much appreaciated.

Thanks, Sören

Quote:

Originally Posted by wersoe (Post 230287)

Code:

#include "udf.h"



DEFINE_ON_DEMAND(write_data)

{

  cell_t c;

  int ID = 2; 

       /* Zone ID for wall-1 zone from Boundary Conditions panel */

  Domain *mixture_domain = Get_Domain(1);

  Domain *subdomain = DOMAIN_SUB_DOMAIN(mixture_domain,0);

  Thread *thread = Lookup_Thread(subdomain, ID);



  FILE *output=fopen ("epsilon.out","w");



  begin_c_loop(c, thread)

     {

        fprintf(output,"\nvof=%e", C_VOLUME(c,thread)); 

     }

  end_c_loop(c, thread)

fclose(output);

}

This UDF writes C_VOF for all cells, not only primary phase
eventhough C_VOF(c,pt[1])

Code:

#include "udf.h"



DEFINE_ON_DEMAND(print_vof)



{

Domain *mix_domain = Get_Domain(1);

Thread *mix_thread;

Thread **pt;



mp_thread_loop_c(mix_thread, mix_domain, pt)

{

cell_t c;

begin_c_loop(c, pt[1])



Message("cell volume fraction = %f\n",C_VOF(c,pt[1]));



end_c_loop(c, pt[1])



}

}

This UDF writes values for all cells too.
Eventhough if(C_VOF(cell,subthread) = 1)

Code:

#include "udf.h"



DEFINE_ON_DEMAND(print_id)

{

Domain *mixture_domain = Get_Domain(1);

Domain *s_d = DOMAIN_SUB_DOMAIN(mixture_domain,0);        /*subdomain pointer, locally defined*/

Thread *mixture_thread;

cell_t cell;



int p_d;         /* loop counter for phase_domain_index, locally defined*/

int p_d_id;         /* mix_domain is available*/



FILE *output=fopen ("epsilon.out","w");

fprintf (output, "energy dissipation rate distriubtion\n");

fprintf (output, "epsilon,volume\n");

int phase_domain_index=0;



sub_domain_loop(s_d, mixture_domain, phase_domain_index)

  {

    /* loop over all cell threads in the primary phase domain  */

            thread_loop_c(mixture_thread,s_d)

             {

                /*Thread *st = THREAD_SUB_THREAD(cell_thread, 0);*/

            /* loop over all cells in primary phase cell threads  */

                       begin_c_loop(cell,mixture_thread)

                {

            /*if(C_VOF(cell,mixture_thread) = 1)*/

            Message("\nDone... %g", C_VOF(cell,mixture_thread));

            fprintf(output,"\nDone...");

            }

            end_c_loop(cell,mixture_thread)

        }

  }    

fclose (output);



}

Hi Soren,
Try this code:

Code:

DEFINE_INIT(my_init_function, domain)

{

  Thread *t;

  Thread **pt;

  Thread **st;

  cell_t c;

  Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,P_PHASE);

  Domain *sDomain = DOMAIN_SUB_DOMAIN(domain,S_PHASE);

  

  real xc[ND_ND], y, x;



      mp_thread_loop_c (t,domain,pt)

    if (FLUID_THREAD_P(t))

      {

        Thread *tp = pt[P_PHASE];



        begin_c_loop (c,t)

          {

     C_CENTROID(xc,c,t);

     x=xc[0];

     

      if ( x > 0.02)

      C_VOF(c,tp) = 0;

      else

      C_VOF(c,tp) = 1;



          }

          end_c_loop (c,t)

         }

         

               mp_thread_loop_c (t,domain,st)

    if (FLUID_THREAD_P(t))

      {

        Thread *sp = st[S_PHASE];



        begin_c_loop (c,t)

          {

     C_CENTROID(xc,c,t);

     x=xc[0];

     

      if ( x > 0.02 )

      C_VOF(c,sp) = 1;

      else

      C_VOF(c,sp) = 0;



          }

          end_c_loop (c,t)

         }

}