 ## Fluids

• rmoss06
Subscriber

Hi,

I am trying to simulate a Electrostatic Precipitator in Fluent. I have my PM10 injection flowing through my mesh, and my last step is to create a UDF which simulates an electric force acting on the particles. I modified the magnetic force code from the Ansys UDF manual as follows, below, then I place the c file in the folder with my project files, interpret the UDF, select it from the dropdown under UDF in my PM injection, initialize and calculate. During the iteration, I get the following error: chip-exec: electric_force: wrong return type: void udf function expectednumber tracked = 19, escaped = 19

I'm very new to using UDFs so I was wondering if anyone my be able to point me in the right direction as to where I went wrong.

Thanks

/* UDF for computing the electric force on a charged particle */

#include "udf.h"

#define Q 7.0     /* particle electric charge   */

#define E 3.0    /* electric field magnitude */

#define TSTART 0  /* field applied at t = tstart  */

/* Calculate electric force on charged particle.  */

/* velocity with electric field: Fx= q*bz*Vy, Fy= -q*bz*Vx */

DEFINE_DPM_BODY_FORCE(electric_force, p, i)

{

real bforce[ND_ND] = 0;

if (P_TIME(p) >= TSTART)

{

if (i == 0) bforce[i] = Q * E*P_VEL(p);

else if (i == 1) bforce[i] = -Q * E*P_VEL(p);

}

else

bforce[i] = 0.0;

/* an acceleration should be returned */

return (bforce[i] / P_MASS(p));

}

• YasserSelima
Subscriber
try this ..
#include "udf.h"

#define Q 7.0/* particle electric charge*/

#define E 3.0/* electric field magnitude */

#define TSTART 0/* field applied at t = tstart*/
DEFINE_DPM_BODY_FORCE(electric_force, p, i)
{
real bforce = 0;
if (P_TIME(p) >= TSTART)
{
if (i == 0) {
bforce = Q * E*P_VEL(p);
} else if (i == 1) {
bforce = -Q * E*P_VEL(p);
} else {
bforce = 0.0;
}
}
/* an acceleration should be returned */
return (bforce / P_MASS(p));
}

Let me know if you are still getting the same error
• rmoss06
Subscriber
Thanks Yasser, thatÔÇÖs seemed to work. I can compile it now and apply it as a body force, the body force doesnÔÇÖt seem to be affecting my particle motion at all, but at least this is a big step forwards, appreciate it!
• Rob
Ansys Employee
Continues here to work out why the particles aren't doing anything!
https://forum.ansys.com/discussion/26079/body-force-not-affecting-particle-motion#latest 