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-   -   DEFINE_INIT PROBLEM (http://www.cfd-online.com/Forums/fluent/49011-define_init-problem.html)

Craig August 13, 2008 18:11

DEFINE_INIT PROBLEM
 
/* 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) } }


Craig August 13, 2008 18:16

DEFINE_INIT PROBLEM DESCRIPTION
 
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?


Smith_K August 14, 2008 01:28

Re: DEFINE_INIT PROBLEM DESCRIPTION
 
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,


Craig August 14, 2008 17:34

Re: DEFINE_INIT PROBLEM DESCRIPTION
 
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.



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