/* This function initializes my domain on the left side with species 0 at 300K and species 1 at 600K on the right side. domain is 1 meter long */

#include "udf.h"

DEFINE_INIT(my_init_function,d) { cell_t c; Thread *t; real xc[ND_ND];

thread_loop_c(t,d) {

begin_c_loop_all (c,t)

{

C_CENTROID(xc,c,t);

if (xc[0] < 0.5)

{

C_T(c,t) = 300.;

C_YI(c,t,0) = 0.;

}

else

{

C_T(c,t) = 600.;

C_YI(c,t,0) = 1.;

}

}

end_c_loop_all(c,t) } }

The above UDF compiles and runs when hooked. The temperature on the left is 300K and the temp on the right is 600K. Species 0 is on the left and Species 1 is on the right.

However, when i zoom into the walls on the right side, the wall nodes appear to be initialized with Species 0.

I think that I need to add an f_loop to initialize nodes on the wall but the temperature loop seemed to work fine. Any ideas?

Assign the species mass fraction in the wall boundary conditions. By default the mass fraction of all the species will be zero. You do not need a UDF to assign the same on the walls. Regards,

Thanks for the response.

My wall boundary is set to: Zero Diffusive Flux for species and 0 Heat Flux for Temp. So, my wall species and Temp is allowed to float based on what happens in the interior.

When I initialize the domain to one temp and species without the UDF using solve/initialize I see that all interior nodes and wall nodes are at the initialized species and temperature.

When I initialize the domain using my UDF I find that only the interior nodes are properly initialized (because I have only looped on cell centroids).

Since I don't want to specify species or temp as a boundary condition, I believe that I must do something extra with my UDF to initialize the remaining part of my domain that my begin_c_loop missed.

Thanks again.

[Kedar G. Bhide]

I've UDF that defines species mass fraction in the form of a profile.


#include "udf.h"
2 DEFINE_INIT(my_init_func, d)
3 {
4 cell_t c;
5 Thread *t;
6 real xc[ND_ND];
7 real x;
8 real phiphi;
9 real l1;
10 real l2;
11 real loc;
12 real dl;
13 real k;
14 int i;
15 Material *m, *sp;
16 printf("\n end of variables declarations");
17 l1=0.0;
18 l2=0.004;
19 loc=0.0;
20 k=2500.0;
21 thread_loop_c(t,d)
22 {
23 begin_c_loop_all(c,t)
24 {
25 C_CENTROID(xc,c,t);
26 loc=xc[0];
27 phiphi=((1.0/(1.0+exp(-2*k*(loc-l1))))-(1.0/(1.0+exp(-2.0*k*(loc-l2)))));
28 if(xc[0] < 0.002)
29 {
30 phiphi=1.0;
31 }
32 /* m=THREAD_MATERIAL(t);
33 mixture_species_loop(m,sp,i)
34 {
35 printf("\n %d",i);
36 }*/
37 C_T(c,t)=300.0+phiphi*1360.0;
38 C_YI(c,t,0)= 1.0*phiphi;
39 C_YI(c,t,1)= 1.0*(1-phiphi);
40 C_YI(c,t,2)= 0.0;
41 C_YI(c,t,4)= 0.0;
42 C_YI(c,t,4)= 0.0;
43 C_YI(c,t,5)= 0.0;
44 }
45 end_c_loop_all (c,t)

It gets hooked and executes without showing any error. However, only temperature gets initialized as per the equation. Mass fractions continue to remain zero.