[m.pirani95]

Hello and have a good time
I want to model a two-phase compressible flow using the VOF method in fluent.
I have a problem on defining the properties of phases.

1)
Is there any problem when I specify the properties of each phase using the DEFINE_PROPERTY macro? I need to specify the phase THREAD or use the mixture THREAD?
2)
When i use the mixture THREAD for C_P(c,t) & C_T(c,t),the fluent determines the properties of the mixture for the calculations by it self?

To understand more:
Which one is correct?
#include "udf.h"

#define C_P_air_0 1006.43 /*j/kg-k*/
#define T_air_0 298.15 /*k*/
#define dens_air_0 1.184 /*kg/m3*/
#define gam_air_0 1.401 /*-*/
#define P_air_0 101325.0 /*pa*/
#define R_air_0 288.0 /*j/kg-k*/

DEFINE_PROPERTY(density_of_air,c,t)
{
cell_t c;
real pi_air_0,P_air,T_air,dens_air;

pi_air_0=(((gam_air_0-1)*dens_air_0*C_P_air_0*T_air_0)/gam_air_0)-P_air_0; /*pa*/

P_air=C_P(c,t); /*pa*/
T_air=C_T(c,t); /*k*/

dens_air=((P_air+gam_air_0*pi_air_0)/(R_air_0*T_air)); /*kg/m3*/


return dens_air;
}



or


#include "udf.h"

#define C_P_air_0 1006.43 /*j/kg-k*/
#define T_air_0 298.15 /*k*/
#define dens_air_0 1.184 /*kg/m3*/
#define gam_air_0 1.401 /*-*/
#define P_air_0 101325.0 /*pa*/
#define R_air_0 288.0 /*j/kg-k*/

DEFINE_PROPERTY(density_of_air,c,t)
{
cell_t c;

t_air=THREAD_SUB_THREAD(t,0);
real pi_air_0,P_air,T_air,dens_air;

pi_air_0=(((gam_air_0-1)*dens_air_0*C_P_air_0*T_air_0)/gam_air_0)-P_air_0; /*pa*/

P_air=C_P(c,t_air); /*pa*/
T_air=C_T(c,t_air); /*k*/

dens_air=((P_air+gam_air_0*pi_air_0)/(R_air_0*T_air)); /*kg/m3*/


return dens_air;
}