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UDF to change particle integration step and print it

- June 22, 2026 at 3:08 am
  
  aniruddhabose96
  Subscriber
  
  Hi
  I am using DEFINE_DPM_TIMESTEP to change the particle tracking time step following UDF manual, but when i am printing it using DEFINE_SCALAR_UPDATE, it is printing Fluents default time step value. What is the issue here? I have attached my UDF below.
  #include "udf.h"
  #include "dpm.h"
  
  DEFINE_DPM_TIMESTEP(my_dt,tp,dt)
  {
  if(dt<0.001)
  {return 1;}
  return dt;
  } /*UDF to check particle time step*/
  
  DEFINE_DPM_SCALAR_UPDATE(store_vel,c,t,initialize,tp)
  {
  if (initialize)
  return;
  
  Message("part time step=%e\n",TP_DT(tp));
  
  }
- June 22, 2026 at 8:33 am
  
  Rob
  Forum Moderator
  
  I assume you hooked it up?
- June 22, 2026 at 1:48 pm
  
  aniruddhabose96
  Subscriber
  
  Yes like Function-compiled and then Build and load and then hooked it in respective area. It is printing Fluents default time step and not my given step.
- June 22, 2026 at 2:21 pm
  
  Rob
  Forum Moderator
  
  What did you set in the DPM panel?

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