Hello,

I try to find the particle position using macro P_POS(p)[i]. But when Fluent interpret the source code, an error "undeclared variable" occurred.

Why? How to solve this problem?

Thank you in advance. Tom

It is hard to tell with the given details.

It could be because of any variable, which hasn't been declared before its use.

One other thing i get in mind is, does your UDF supplies the pointer p access? If not, you need to provide that with the argument ' Tracked_Particle *p '.

Hello, Umesh, Thank you. I found out it is not necessary to provide the argument ' Tracked_Particle *p '. The following is a very simple UDF. But the error still exists.

#include "udf.h"

DEFINE_DPM_BODY_FORCE(particle_body_force, p, i) {

real bforce = 0.0;

real x = P_POS(p)[1];

return (bforce/P_MASS(p)); }

Waiting for your reply. Thanks. Tom.

Hi Tom,

I think the problem is with the definition of x. I think, P_POS(p)[i] is a position vector and so you need to define x as a vector with syntax, 'real x[ND_ND]'. Then, you can access the x component of the position with, x[1] = P_POS(p)[1]. Try this out. It may solve yr problem.

hello,

I would like to get the face area the particle is crossing to get the volume flux.

But I'm not sure which variable I should use and how:

C_FACE(cell,cthread)?

#include "udf.h"

#include "dpm.h"

#include "surf.h"

#define REMOVE_PARCELS FALSE

#define P_CELL(P) RP_CELL(&((P)->cCell)) /* Non-standard macros */

#define P_CELL_THREAD(P) RP_THREAD(&((P)->cCell))

real volume;

real face;

Particle *p;

cell_t cell;

face_t f;

Thread *cthread;

real r, x, y;

DEFINE_DPM_OUTPUT(Discrete_phase_sample,header,fp, p,t,plane)

{

#if RP_3D

real flow_time = solver_par.flow_time;

cell = P_CELL(p); /* Get the cell and thread that the particle

is currently in */

cthread = P_CELL_THREAD(p);

face = C_FACE(cell,cthread);

if(header)

cxprintf(fp," #R [m] x-velocity[m/s] y-velocity[m/s] z-velocity[m/s] Drop Diameter[m] face \n");

if(NULLP(p))

return;

x = p->state.pos[0];

y = p->state.pos[1];

r = sqrt(SQR(x) + SQR(y));

cxprintf(fp," %e %f %f %f %e %e \n",

r,p->state.V[0],p->state.V[1],p->state.V[2],P_DIAM(p),volume);

#endif

#if REMOVE_PARCELS

p->stream_index=-1;

#endif

}

Can anyone help?

thank you

David

i think, when you use UDF in DPM, you must compile the UDF, rather than interpret the file.

When you compile any udf, you muss install the VC++ in your computer, then all is ok.

Hello, Annie, Thank you. It works. Tom

[NH_Aus]

Hi,
I need to know the shortest distance of wall from the particle location. I know I can use C_WALL_DIST(c,t) this, but how do I connect from:
px=P_POS(p)[0] ;
py=P_POS(p)[1] ;
pz=P_POS(p)[2] ;
??

[Parham Vatankhah]

Hi all,

By interpreting UDFs you can not access particles position.
Generally, it's better to compile complex UDFs.

best regards,

Parham