[FlavioC]

Hello to everyone, I am working in a particle trap condition when particles satisfies that 0.001>vrel, where vrel is the fluid velocity minus the particle velocity. This is my code:

#include "udf.h"
DEFINE_DPM_BC(best_dpmbc3,p,t,f,f_normal,dim)
{
    /*Variable declarations*/
    int i;  /*working counter for script*/
    real vrel;
    real rx, ry, rz;  
    /*Variable evaluations*/    
    cell_t c;    
    c=P_CELL(p);
    rx=C_U(c,t)-P_VEL(p)[0];
    ry=C_V(c,t)-P_VEL(p)[1];
    rz=C_W(c,t)-P_VEL(p)[2];
    vrel = sqrt(rx*rx+ry*ry+rz*rz);
        if(0.001 > vrel)
       {
        for(i=0; i<dim; i++)
        P_VEL(p)[i] = 0;
        return PATH_ABORT;
        }
    /*Stop tracking the particle*/
    else 
	{
	return PATH_ACTIVE;
	}
}

It can be compiled without any problema but when I select this udf in the boundary condition panel , fluent gave me this message:
Error: received a fatal signal (Segmentation fault).Error Object: #f
I am novice in the UDF area, can someone give me suggestions or opinions please?

[AlexanderZ]

you are using C_U(c,t) macro but c has nothing inside
you should make loop over cell/threads to use C_U(c,t)

thread_loop_c(t,domain)
{
begin_c_loop(c,t)
{
code
}
end_c_loop(c,t)
}

best regards

[FlavioC]

Hello AlexanderZ.

Thanks for you replay. I really appreciate your answer. Could you please give me some help on the uses of loop macro, I have been reading about it, but all my attempts have failed.

[AlexanderZ]

I've already gave you a tip.
More information in Ansys Fluent Customization manual

best regards

[FlavioC]

Thanks for you help. I will try.

[AlexanderZ]

I was wrong there.
I your code c and thread were defined so you don't need a loop.

I have no experience with DPM but it seems like DEFINE_DPM_BC macro is defined on boundary (face) only, so any data related to cells is not avaliable.
You may try to get the data from cell,which is adjusted to this face using

c0 = F_C0(f,t);
t0 = THREAD_T0(t);

however, I/m not sure how it will work

on the other hand, in UDF manual there is some macro WALL_F_VV(f,thread)[i]
there is no information how it works.
You may try to find something in Ansys Fluent Customization manual in DEFINE_DPM_BC chapter

best regards