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Old   July 12, 2015, 09:48
Default UDF Surface Reaction Basics
Matthew Rich
Join Date: Jul 2013
Posts: 33
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Hi all

I am attempting to create a UDF file to have product species produced at the surface of a tube wall. I have been reviewing the manual and I sort of have an but I need someone to help me connect the dots. My understanding is it requires two steps.

1) Identify the involved cells


  Domain *d = Get_Domain(1); /* POINTER FOR THE DOMAIN */
  Thread *t, *t0;
  cell_t c0;
  face_t f;
  t = Lookup_Thread(d, zone_id); /* POINTER FOR THE SPECIFIED BOUNDARY */
      c0 = F_C0(f,t);
      C_UDMI(c0,t0, 0) = 1;
So this was largely borrowed from others but I think it is correct. My hope is that I would enable this with initialization function hook. I will have surface cells based on the BC I pass through Zone_ID. Now where I get slightly confused is on the C_UDMI and how I can link that with step 2.

2) Implement the Source term on the species balance equations
  real k, source;
  k = 0.5; /* 1/s */
  source = C_R(c,t)* k * C_YI(c,t,0); /* source is a function of k times mass fraction of first species times density */
  dS[eqn] = 0.0;
  return source; /*Unit should be kg/(m3-s)*/
I would implement this by going to the species tab and the balance equations of my species. I am running on R16.1 and the UDF is interpreted and not compiled. Now here is where my problems start. My DEFINE_ON_DEMAND equations fails and crashes out FLUENT. I am running the problem as a Local MPI job with 4 processors. When I hybrid initialize i get the following error.

iter scalar-0

1 1.000000e+00
2 2.503153e-04
3 3.350463e-05
4 1.917379e-05
5 3.410960e-06
6 9.846552e-07
7 2.790700e-07
8 9.536242e-08
9 3.064283e-08
10 1.126697e-08
hybrid initialization is done.

================================================== ============================

Node 0: Process 5300: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 2: Process 8916: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 3: Process 8584: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 1: Process 3420: Received signal SIGSEGV.

================================================== ============================
MPI Application rank 0 exited before MPI_Finalize() with status 2
The fl process could not be started.

===============Message from the Cortex Process================================

Fatal error in one of the compute processes.

================================================== ============================

Error: Cortex received a fatal signal (unrecognized signal).
Error Object: ()

Error: There is no active application.
Error Object: (rp-var-value 'vof/oc/n-waves)

Not sure what I need to do to resolve that. I have no errors implementing the DEFINE_SOURCE by itself but I get zero production of the species in question. Any assistance or recommendation of resources would be much appreciated in getting this working. Also I am not sure how the species function knows how to hook into the Cells identified to participate in the surface reaction.

Thanks in advance.
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Old   July 14, 2015, 19:24
Matthew Rich
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Anyone have comments on this. I know there is a similar thread but the solution applied is not clear.

Any help is much much appreciated.
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