[keith08]

Hello, everyone.

I'm using DPM model to simulate the flow of air and water droplets, where droplets are regarded as discrete phase. Now I need give an force for motion of droplets.
Fx=-2.4*(ux-4)/ √t
Fy=-2.4*(uy)/ √t
And i used DEFINE_DPM_BODY_FORCE macro. Here is the case.

#include "udf.h"
#define TSTART 0.0 /* field applied at t = tstart */
DEFINE_DPM_BODY_FORCE(particle_body_force, p, i)
{
real bforce;
if(P_TIME(p)>TSTART)
{
if(i==0) bforce=-2.4*(P_VEL(p)[0]-4)/sqrt (P_TIME(p));
else if(i==1) bforce=-2.4*(P_VEL(p)[1]-0)/sqrt (P_TIME(p));
}
else
bforce=0.0;
/* an acceleration should be returned */
return (bforce/P_MASS(p));
}
Fluent shows it’s right. But it works very slowly. Even max number of steps is very big, like 100000000, it shows the particle trajectory is still incompleted.
I hope you can tell the reason if you know. Thank you!