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-   -   Time step of steady particle tracking (http://www.cfd-online.com/Forums/fluent/69061-time-step-steady-particle-tracking.html)

payam_IUST October 10, 2009 16:38

Time step of steady particle tracking
 
Hi
I am using steady particle tracking and then generate step by step file to see positions of particle at evrey time step.unfortunately the time step that fluent considers is very small(ebout 1e-6) and I want to change it(to about 1e-2),but however I change length scale or step length,the time step does not chang effectively,I even examined this udf to change time step :


#include "udf.h"
#include "dpm.h"

DEFINE_DPM_TIMESTEP(PAYAM,p,dt)
{
return 0.1;
return dt
}

but nothing changes!
Anyone can help me?:confused:

Andrej October 12, 2009 08:19

Probably you can not make time step more , then
length of Cell divided by the Velocity of the particle in cell. CFL Number in Cell can not be more then 1.0.


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