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Old   November 25, 2009, 05:19
Default initialization species UDF
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Hello everyone,
this UDF syntax of the initialization of different-density of species is it correct?
thank you for your answer

///////////////////////////////////////////
DEFINE_INIT(udf_init_temp, domain)
{
cell_t c,c0,c1,c2,c3,c4;
Thread *t,*t0, *t1, *t2,*t3, *t4;
real coord[ND_ND];

thread_loop_c(t,domain)
{
begin_c_loop_all(c,t)
{
C_CENTROID(coord,c,t);
if (coord[1] < 0.0005)
C_T(c,t) = 10000.0;
C_R(c0,t0)= 1E24; /* densiy of Ar */
C_R(c1,t1)= 2E22; /* density of Ar+ */
C_R(c2,t2)= 1E2; /* density of Ar2+ */
C_R(c3,t3)= 1E2; /* density of Ar3+ */
C_R(c4,t4)= 2E22; /* density of electrons */

}
end_c_loop_all(c,t)
}
}
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Old   November 25, 2009, 07:25
Default It needs modifications
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Hi Louiza,
Your udf lacks correct values for c0, c1, c2, c3, c4, t0, t1, t2, t3, t4. It should give you segmentation fault.
First of all, I don't think you can set the density for species, but the mass fraction. In your case, the modification should be as following:
Code:
///////////////////////////////////////////
DEFINE_INIT(udf_init_temp, domain)
{
   cell_t c;
   Thread *t;
   real coord[ND_ND];

   thread_loop_c(t,domain)
   {
      begin_c_loop_all(c,t)
      {
         C_CENTROID(coord,c,t);
         if (coord[1] < 0.0005) 
         C_T(c,t) = 10000.0;
         C_YI(c,t,0)= 1E24; /* mass fraction of Ar */ 
         C_YI(c,t,1)= 2E22; /* mass fraction of Ar+ */
         C_YI(c,t,2)= 1E2; /* mass fraction of Ar2+ */ 
         C_YI(c,t,3)= 1E2; /* mass fraction of Ar3+ */
         C_YI(c,t,4)= 2E22; /* mass fraction of electrons */

      }
      end_c_loop_all(c,t)
   }
}

Last edited by dmoroian; November 25, 2009 at 09:27.
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Old   November 25, 2009, 09:13
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Hi Dragos Moroianu

Thank you for your relpy, exactely with this UDF, i receive message error "segmentation violation".
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Old   November 25, 2009, 09:19
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I have just the density of species, how i can calculate mass fraction, have you any idea?
thank you
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Old   November 25, 2009, 09:53
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Hello Louiza,
The udf I posted should not crash if you have defined 5 species!

density = mass/volume => mass = density*volume

Dragos
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Old   November 25, 2009, 10:55
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Hi Dragos

Your UDF works fine without error, i have another question please, i need to initialize the mass fraction of species in temperature 10000 K trought UDF, and this same species in 1000 k in the pannel solve>initialize.

can i initialize all species at 1000 and 10 000k througt UDF?

my second question:

mass=density/volume, i 'm very bad in kinetic law how a calculate a volume, can i use pv = nRT?

Thank you dragos
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Old   November 26, 2009, 04:05
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Hi Louiza,
I suspect you have one number for each species, representing the average density of that species in the entire computational domain. It this is the case, then the volume we are talking about is ... the entire domain.
In this approach (transport species), the temperature is defined only for the mixture, not for each species individually. Otherwise, you have to take another approach (Euler/Euler maybe).

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Old   November 26, 2009, 04:56
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Hi Dragos

Thank you for your answer.
Good day

louiza
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