help: define volume of fraction using UDF in VOF
 

The following is my udf program. I try to define the volume of fraction of phase-2 by this udf. The contour of volume of fraction shows a result not as I expected after I initiate the solution.

If I changed the sentence in udf, like if xc[2]<0.1, the contour shows volume of fraction of both phases are zero everywhere. what's the problem is? Any help is appreciated.

/*"udfmak.c" UDF for specifying an initial liquid volume fraction zone ************************************************** *******/

#include "udf.h"

DEFINE_INIT(my_init_function, mixture_domain) {

#define Pi 3.14159265 int phase_domain_index; cell_t cell; Thread *cell_thread; Domain *subdomain; real xc[ND_ND];

sub_domain_loop(subdomain,mixture_domain,phase_dom ain_index) {

if(DOMAIN_ID(subdomain)==3)

thread_loop_c(cell_thread,subdomain)

{

begin_c_loop_all(cell, cell_thread)

{

C_CENTROID(xc,cell,cell_thread);

if (xc[2]<0)

{

C_VOF(cell,cell_thread)=0;

}

if (xc[2]>0)

{

if (xc[1]<-2.50e-7)

{

C_VOF(cell,cell_thread) =1;

}

else if ((xc[1]>=-2.50e-7) && (xc[1]<2.50e-7))

{

if (xc[2]<1.50e-7*sin(Pi*xc[1]/5.00e-7+Pi/2.))

{

C_VOF(cell,cell_thread)=0;

}

else

{

C_VOF(cell,cell_thread)=1;

}

}

if(xc[1]>=2.50e-7)

{

C_VOF(cell,cell_thread)=1;

} }

}

end_c_loop_all (cell,cell_thread)

}

} }