[hooman.esl]

Hi dear all,
I am trying to write a UDF for mass source term in continuity equation in porous media condition. my problem has 3 phases (water(liquid), methane and hydrate(solid)).
i want to add this source term for methane phase:

mg = c* Sh * (Pe - P);
mg: mass generation of gas
Sh: saturation of hydrate
p: pressure
pe: equilibrium pressure

my problem is that how can i access to hydrate saturation or volume fraction when i am writing UDF for methane phase???

for two phase flow i used this code:

b=C_VOF(c,t); /* vol fraction of methane */
a=porosity-b; /* vol fraction of water */
sat_w=a/porosity; //saturation for water

but in three phase i need the volume of fluid of water to calculate hydrate saturation:
Saturation of hydrate+Saturation of methane+Saturation of water=1
can any one help me?