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Error running UDF for water evaporation-condensation problem

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Old   July 5, 2023, 23:28
Default Error running UDF for water evaporation-condensation problem
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Mat
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I am encountering an error while trying to run a UDF in ANSYS Fluent for a water evaporation-condensation problem. The purpose of the UDF is to calculate the saturation pressure. In my simulation, phase 1 represents water in the liquid state, while the other phase represents a mixture of air and water vapor.

I have successfully compiled the UDF code without any errors or warnings. Additionally, I have assigned the saturation temperature in the "Saturation" tab within the "Evaporation-Condensation" settings. However, when I attempt to perform the initialization step, I encounter the following error:

--------------------------------------------------------------------------------------
Node 0: Process 28764: Received signal SIGSEGV.
The fl process could not be started.
--------------------------------------------------------------------------------------

Based on my understanding of the problem, I believe that the error might be occurring within the "mixture_species_loop" of my UDF. Interestingly, everything seems to work fine before this part. I would greatly appreciate any insights or suggestions regarding the possible reasons behind this error.

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#include "udf.h"
#define MOLAR_MASS_WATER 18.01534 /* g/mol*/
#define MOLAR_MASS_AIR 28.97 /* g/mol*/
#define RHO_WV 0.5542 /* kg/m3*/
#define RHO_AIR 1.225 /* kg/m3*/
DEFINE_PROPERTY(saturation_temp,c,t) /* t: mixture thread, c: cell variable, Cell volume*/
{

real vol = C_VOLUME(c, t);

Thread *pt = THREAD_SUB_THREAD(t, 0); /* Primary phase thread-water*/
Thread *st = THREAD_SUB_THREAD(t, 1); /* Secondary phase thread-air-vapour mixture template*/

real vf_s = C_VOF(c, st); /* Get the volume fraction of secondary phases*/
real vf_p = 1 - vf_s; /* Get the volume fraction of primary phases*/

real p_mix = C_P(c, t); /* Get the pressure of the mixture */
real p_op = RP_Get_Real("operating-pressure"); /* Get the operating pressure*/
real rho_p = C_R(c, pt); /* Primary phase density*/


/* Get mass fractions in primary phase*/
real mf[2]; /*to store mass fractions*/
Material *m = THREAD_MATERIAL(pt);
Material *sp = NULL;
int i; /* Species index - 0 for water vapor and 1 for air+vapour*/
mixture_species_loop(m, sp, i)
{
mf[i] = C_YI(c, pt, i);
}
real p_w; /* Water vapor pressure for the cell*/
if (vf_s == 1) /* If secondary phase only*/
{
p_w = p_mix + p_op;
}
else /* If primary phase or mixture of phases*/
{
/* Find the partial pressure of water vapour, partial pressure = cell pressure * water mole fraction*/
real m_prim = rho_p * vol * vf_p; /* mass of primary phase in cell*/
real m_wv = mf[0] * m_prim; /* mass of water vapour in cell*/
real m_air = m_prim - m_wv; /* mass of air in cell*/
real N_wv = m_wv / MOLAR_MASS_WATER; /* No of moles in water vapour*/
real N_air = m_air / MOLAR_MASS_AIR; /* No of moles in air*/
real N_total = N_wv + N_air; /* total moles*/
p_w = (C_P(c, t)+ p_op)* (N_wv / N_total); /* water vapour partial pressure*/
}
real t_sat;
t_sat = (1730.63 / (10.196 - log10(p_w))) + 39.724; /* Calculate saturation temperature*/
return t_sat;
}
--------------------------------------------------------------------------------------
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evaporation condensation, mixture model., multiphase, saturation temeprature

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