[khayrulbuet13]

Hi good people,
I am trying to simulate a filter with 90% efficiency. So I am using 2 UDF. DEFINE_DPM_BC for killing 90% particle that touches the outlet boundary and DEFINE_DPM_SCALAR_UPDATE to update the position of particle from outlet to inlet for recycling the 10% particle. Till now everything works fine. But It seems I also need to update the velocity because once the particle recycled they continue to move towards the negative x-direction.
I tried to fix the issue by updating the velocity also but it is not working. I tried with P_VEL(p)[1] = positive and negative value. but for both of the cases, the particle moves towards the negative y-direction.

** here I am attaching my UDF

Can you please take a look and help me in this regard?

#include "udf.h"
#include <stdlib.h>
#include <time.h>
DEFINE_DPM_BC(bc_reflect,p,t,f,f_normal,dim)
{
float my_rand,init_vel;

init_vel = - 0.272;
srand ( time(NULL) );
my_rand=rand() %100;

if (my_rand <= 1)
{
return PATH_END;
}
else
{
P_VEL(p)[0] = 0;
P_VEL(p)[1] = init_vel;
return PATH_ACTIVE;
}
}



DEFINE_DPM_SCALAR_UPDATE(recycle_particles,c,t,ini tialize,p)
{
FILE *fp;
float temp_rand, pos_rand, inlet_max;
inlet_max = 0.4;
srand ( time(NULL) );
temp_rand = rand() % 100;
pos_rand = (temp_rand/100)*inlet_max;

if (P_POS(p)[0] <= 0.4 && P_POS(p)[1] <= 0.7)
{
P_POS(p)[0] = pos_rand;
P_POS(p)[1] = 0.75 ;

}
}

[AlexanderZ]

I don't have much experience in DPM, but
shouldn't you modify velocity in update_scalar macro, as DEFINE_DPM_BC seems to be a boundary condition?

DEFINE_DPM_SCALAR_UPDATE(recycle_particles,c,t,ini tialize,p)
{
// your code
P_VEL(p)[0] = 0;
P_VEL(p)[1] = init_vel;
}