source term in multiphase flow+Urgent

sara

I have a two phase problem, one phase is air and the other phase is water, I wrote a source term to add in mass equation of air, although, there is not any error during the interpret of the udf, but the flow field doesn't change. I've attached my udf. Thank You sara #include "udf.h" #define C2 .0009672 DEFINE_SOURCE(mass_source,c,t,dS,eqn) { real xc[ND_ND]; real source, vf, vol, den; vf = C_VOF(c,t); vol = C_VOLUME(c,t); den = C_R(c,t); source = -1*C2*den*(pow(vf,0.6667)/pow(vol,0.333)); dS[eqn] = 0.0; C_CENTROID(xc,c,t); if (xc[1] == 0.84) source =source+80.84; else source =source+0.0; return source; }