[Kimia]

Hi all.
I want to write a UDF code to define a hemisphere interface of a water droplet and vapor phase in surroundings for simulating evaporation. I am a beginner user of UDF. My guessing is that I should use DEFINE_INIT macro. I followed one example in UDf manual, but I am not sure about using loop over cells or faces. I also don't know how to define the boundary. should I use C_vof to define volume fraction for each phase?

[Bruno Machado]

Originally Posted by Kimia

Hi all.
I want to write a UDF code to define a hemisphere interface of a water droplet and vapor phase in surroundings for simulating evaporation. I am a beginner user of UDF. My guessing is that I should use DEFINE_INIT macro. I followed one example in UDf manual, but I am not sure about using loop over cells or faces. I also don't know how to define the boundary. should I use C_vof to define volume fraction for each phase?

The initial conditions can be looped all over the cells.

To define the boundary, use DEFINE_PROFILE macro.

[Kimia]

Originally Posted by Bruno Machado

The initial conditions can be looped all over the cells.

To define the boundary, use DEFINE_PROFILE macro.

Hi Bruno. Thank you so much for your response.

For defining a hemisphere shape of the initial interphase between liquid and vapor, I am using the code below. Does it seem correct? I could not compile it successfully though. Apparently something is wrong with it.



#include "udf.h"
/* domain pointer that is passed by INIT function is mixture domain */
DEFINE_INIT(my_init_function, mixture_domain)
{
int phase_domain_index;
cell_t cell;
Thread *cell_thread;
Domain *subdomain;
real xc[ND_ND];

/* loop over all subdomains (phases) in the superdomain (mixture) */
sub_domain_loop(subdomain, mixture_domain, phase_domain_index)
{
/* loop if secondary phase */
if (DOMAIN_ID(subdomain) == 3)
/* loop over all cell threads in the secondary phase domain */
thread_loop_c (cell_thread,subdomain)
{
/* loop over all cells in secondary phase cell threads */
begin_c_loop_all (cell,cell_thread)
{
C_CENTROID(xc,cell,cell_thread);
if ((sqrt(ND_SUM(pow(xc[0],2.),pow(xc[1]-3,2.),pow(xc[2],2.)))<1.25 && xc[1]>3 ) )

/* set volume fraction to 1 for centroid */
C_VOF(cell,cell_thread) = 1.;
else
/* otherwise initialize to zero */
C_VOF(cell,cell_thread) = 0.;

}
end_c_loop_all (cell,cell_thread)
}
}
}

[RAJ KIRAN]

Initialization can also be done using GUI in fluent

Adapt->Region->Sphere

There you can mark the region and later initialize VOF value using Solution initialization-> Patch

[Kimia]

Originally Posted by RAJ KIRAN

Initialization can also be done using GUI in fluent

Adapt->Region->Sphere

There you can mark the region and later initialize VOF value using Solution initialization-> Patch

Thank you so much for your help. I used the patch function and it seems that it is working properly.