Hallo, I am trying to simulate a 3D case in which two phase(water and air)are counter-current, namely they come into the calculation region in counter directions. What I am interested in are the free surface between the two phase. In my case the thickness of water is very thin, hereby surface tension can not be ingored and the grid should be very fine. On the other hand, in order to decrease the calculation time, the length for calculation is not enough. That means I'd like to induce a full-developed friction between the two phases to observe the influence of the friction. Now I am wondering whether i can induce the friction into VOF model? I have tried it as a momentum source in UDF but failed. Could somebody help me to check it?

# include "udf.h"

# define rho_g 1.225 # define rho_l 997.

# define Min_VOF 1.e-06 # define Max_VOF 0.999999

# define friction 0.44 # define d 0.001

DEFINE_SOURCE(x_Momentom_source,c,t,ds,eqn) {

real x[ND_ND];

real source,con;

real wvof;

real area,rho;

Thread **pt=THREAD_SUB_THREAD(t,1);

source =0.0;

C_CENTROID(x,c,t);

wvof = C_VOF(c,pt[1]);

if ((wvof>Min_VOF)&&(wvof<Max_VOF))

{

area = C_VOF(c,pt[1])*(1-C_VOF(c,pt[1]))/d;

rho = rho_g*(1-C_VOF(c,pt[1]))+rho_l*C_VOF(c,pt[1]);

con = friction*rho*area;

source = -con * fabs(C_U(c,t))*C_U(c,t);

ds[eqn] = -2.*con*fabs(C_U(c,t));

}

else

ds[eqn]=0.0;

return source;

}

/*I adopt C_U(c,t) to substitute slip velocity between the two phase, it is right?*/

Best regards Flora

Is there anybody who is familar to VOF model? Thanks a lot

Please discuss it with me. I am puzzled! Thank you very much!