[kharnabnew]

Hi all,
I am simulating a multiphase flow in a domain which has one inlet and two outlets. I have gas and liquid and would like to impose a certain flow split based on the fractions of flow rate at the outlets. Using Outflow BC, one can impose a constant flow fraction at each outlet with the total equal to unity. Then, I need to adjust these fractions depending on the volume fraction of one of the phases at a given outlet. It means simply:
If volume fraction of phase x at outlet 1 = value, then adjust the flow rate fraction to value

can Any one advise on which UDF should be used?

Thanks

[kharnabnew]

Hi all,
I managed to get this UDF. So far it calculates the area-averaged volume fraction, at the required boundary, correctly. However, the few commands I added to adjust the outflow boundary condition through input parameter is not working.
Any hints?
Thank you in advance

#include "udf.h"
# define domain_ID 3
DEFINE_ADJUST(face_av,domain)
{
/* Variables used by serial, host, node versions */
int surface_thread_id=0;
real total_area=0.0;
real total_oilvof=0.0;
real gasout_split=RP_Get_Input_Parameter("gasout_flow") ;
domain = Get_Domain(domain_ID);
/* "Parallelized" Sections */
#if !RP_HOST /* Compile this section for computing processes only (serial
and node) since these variables are not available
on the host */
Thread* thread;
face_t face;
real area[ND_ND];
#endif /* !RP_HOST */

/* Get the value of the thread ID from a user-defined Scheme variable */
#if !RP_NODE /* SERIAL or HOST */
surface_thread_id = RP_Get_Integer("oilvof_av/thread-id");
Message("\nCalculating on Thread # %d\n",surface_thread_id);
#endif /* !RP_NODE */
/* To set up this user Scheme variable in cortex type */
/* (rp-var-define 'oilvof_av/thread-id 2 'integer #f) */
/* Once set up you can change it to another thread's ID using : */
/* (rpsetvar 'oilvof_av/thread-id 7) */
/* Send the ID value to all the nodes */
host_to_node_int_1(surface_thread_id); /* Does nothing in serial */
#if RP_NODE
Message("\nNode %d is calculating on thread # %d\n",myid,
surface_thread_id);
#endif /* RP_NODE */
#if !RP_HOST /* SERIAL or NODE */
/* thread is only used on compute processes */
thread = Lookup_Thread(domain,surface_thread_id);
begin_f_loop(face,thread)
/* If this is the node to which face "officially" belongs,*/
/* get the area vector and volume fraction and increment */
/* the total area and total volume fraction values for this node */
if (PRINCIPAL_FACE_P(face,thread)) /* Always TRUE in serial version */
{
F_AREA(area,face,thread);
total_area += NV_MAG(area);
total_oilvof += NV_MAG(area)*F_VOF(face,thread);
}
end_f_loop(face,thread)

Message("Total Area Before Summing %f\n",total_area);
Message("Total Volume fraction Before Summing %f\n",total_oilvof);
# if RP_NODE /* Perform node synchronized actions here
Does nothing in Serial */
total_area = PRF_GRSUM1(total_area);
total_oilvof = PRF_GRSUM1(total_oilvof);
if ((total_oilvof/total_area) > 0)
{
gasout_split = 0.75;
gasout_flow = gasout_split;
}

# endif /* RP_NODE */
#endif /* !RP_HOST */
/* Pass the node's total area and oil volume fraction to the Host for averaging */
node_to_host_real_2(total_area,total_oilvof); /* Does nothing in SERIAL */
#if !RP_NODE /* SERIAL or HOST */
Message("Total Area After Summing: %f (m2)\n",total_area);
Message("Total Oil Volume Fraction After Summing %f (N)\n",total_oilvof);
Message("Average oil volume fraction on Surface %d is %f \n",
surface_thread_id,(total_oilvof/total_area));
Message("Flow weighting ratio at gas outlet is: %f \n",gasout_split);
#endif /* !RP_NODE */
}