Define_source - evaporation: Unit
 

Dear all,

I would like to know the unit of DEFINE_SOURCE for mass flux to be given as input in ANSYS Fluent. I read somewhere is should be kg/m^3 s^1. So I have multiplied by volume. But my question is how does ANSYS Fluent consider the volume for a 2D edge which is my case interior zone of liquid-vapor. This UDF compiles without any error but I am applying this UDF only on interior liquid-vapor.

Macro Argument Types Returns: C_VOLUME(c,t) cell_t c, Thread *t
real cell volume for 2D or 3D,
real cell volume/2 pi for axisymmetric


#include "udf.h"
#include "math.h"

#define M 18.015
#define hfg 2600000.0
#define R 8314.0
#define pi 3.141592
#define pref 101325
#define Tref 373.15
#define pv 15828.0
#define Tv 343.0

DEFINE_SOURCE(mass2,c,t,dS,eqn)
{
real source, pv_eq, Tlv, vol, Acell ;
Domain *d=Get_Domain(1);
int ID=16;
Thread *t_int=Lookup_Thread(d, ID);
face_t f;
real A[ND_ND];
real area = 0.;
begin_f_loop(f,t)
{
F_AREA(A,f,t_int);
area += NV_MAG(A);
Tlv = C_T(c,t);
vol = C_VOLUME(c,t);
pv_eq = pref * exp(((M*hfg)/R) * ((1/Tref)-(1/Tlv)));
source = - 0.857142857 * (Acell/vol) * (1/pow(M/2*pi*R, 0.5)) * ((pv_eq/pow(Tlv, 0.5)) - (pv/pow(Tv, 0.5)));
dS[eqn] = - 0.857142857 * (Acell/vol) * (1/pow(M/2*pi*R, 0.5)) * (pref * exp((M*hfg)/R) * (-((1/Tref) * (0.5/pow(Tlv, 1.5))) + (1.5/pow(Tlv, 2.5))));
}
end_f_loop(f,t)
return source;
}

Volume in 2D
 

It depends on the 2D simulation. For 2D planar, third dimension is 1 m. For 2D axisymmetric, third dimension is radian.