[prebenjs]

Hi,
I want to implement a a reaction happening at a Wall (surface) where the gas phase (primary phase) changes to a liquid phase (secondary phase). It should be noted that these phases are completely different substances undergoing a "reaction" at the surface.

Reading up on the topic it seems like i must implement a UDF on the surface, much like discussed from this previous post:

How to use a UDF to set the volume fraction in the cells next to a wall?

Containing the UDF:
[CODE #include "udf.h"

DEFINE_ADJUST(remove_air,domain)
{
/* Cut-off volume fraction */
real VOF_limit=0.3; /* Volume fraction limit (of air) */

/* Create the thread pointers for the wall */
Thread *t; /* Mixture level thread */
Thread *t_air; /* Phase level thread */
Thread *t_water; /* Phase level thread */
face_t f; /* Face thread */
cell_t c; /* Cell thread */
domain = Get_Domain(1); /* Get the domain */

/* Set thread id's of wall (from Fluent) and phase domain indices */
int surface_thread_id=12; /* Wall thread id */
host_to_node_int_1(surface_thread_id); /* Pass thread id to nodes */
int phase_domain_index_air = 0; /* Air phase index */
int phase_domain_index_water = 1; /* Water phase index */
host_to_node_int_2(phase_domain_index_air, phase_domain_index_water); /* Pass domain index to nodes */


/* Calculate viscous resistance */
real R_V=0.0;
real volume_fraction_air;
real volume_fraction_water;

/* Node calculations */
#if !RP_HOST
/* Find mixture level thread and phase level threads */
t = Lookup_Thread(domain,surface_thread_id);
t_air = THREAD_SUB_THREAD(t, phase_domain_index_air);
t_water = THREAD_SUB_THREAD(t, phase_domain_index_water);

/* Loop through faces on wall */
begin_f_loop(f,t)
{
if (PRINCIPAL_FACE_P(f,t))
{
/* Get thread for adjacent cell */
c = F_C0(f,t);

volume_fraction_air=C_VOF(c,t_air);
volume_fraction_water=C_VOF(c,t_water);
/* Message("Volume fraction air %f\n", volume_fraction_air); */

if (volume_fraction_air >= 0.38 && volume_fraction_air <= 0.39)
{
Message("Volume fraction air: %f\n", volume_fraction_air);
Message("Volume fraction water: %f\n", volume_fraction_water);
}

R_V -= F_STORAGE_R_N3V(f,t,SV_WALL_SHEAR)[0];
}
}
end_f_loop(f,t)

/* Sum values from nodes */
R_V = PRF_GRSUM1(R_V);
#endif
node_to_host_real_3(R_V, volume_fraction_air, volume_fraction_water);

/* Print variables to validate UDF */
#if !RP_NODE
Message("Viscous force: %f [N]\n", -R_V);
Message("Volume fraction air: %f\n", volume_fraction_air);
Message("Volume fraction water: %f\n", volume_fraction_water);
#endif
}][/CODE]

However, it seems like it wasn't solved completely. Is there anybody who can help we with this?