Please help me ( udf for regulation the mass flow rate at the inlet )
 

Hello friends I really need your help

I am trying to control the injection of the mass flow rate at a velocity inlet using a UDF. In fact I want to have the same mass flow rate at the inlet and at the outlet-pressour. So I need to put a condition at my velocity-inlet like if the two mass flow rates are not equal it has to stop injecting ( water ) until they ll be equal
I begun by this UDF, it only needs the regulation part

#include "udf.h"
DEFINE_EXECUTE_AT_END(measure_mass_flow)
{
Domain *d;
real flow=0.;
face_t f;
Thread *t;
t= Lookup_Thread(d, 12);
d = Get_Domain(1);

thread_loop_f(t,d)
{
begin_f_loop(f,t)
{
flow+=F_FLUX(f,t);
}
end_f_loop(f,t)
}
printf("MASS Flow Rate: %g\n",flow);
flow=0.;
}