adaptive time step UDF

tizianoghisu · May 15, 2014, 11:21

Hello everyone,

I wastrying to write a UDF defining an adaptive time step function for a time-dependent simulation ... but i encountered problems even before i arrived to the adaptive part, just by using the DEFINE_DELTAT UDF

while i was doing this, I encountered a very strange problem. While the simulation is stable for a given time step without the UDF, as soon as i use the udf to set the time step, the simulation blows up, even if i use the same time-step i was using earlier. The UDF I am using is very simple

/************************************************** *******************
UDF that changes the time step value for a time-dependent solution
************************************************** ********************/
#include "udf.h"

DEFINE_DELTAT(mydeltat,d)
{
real dt=1.0e-4;
return dt;
}

How is this possible? Any suggestions? Thanks

Tiziano

mahditorabiasr · November 25, 2014, 16:58

Too late reply ;) but maybe works for others...

The problem is a result of using "Extrapolate Variables" option in calculation menu during adaptive time-step calculation (at least in my case).

May 15, 2014, 11:21	adaptive time step UDF	#1
tizianoghisu New Member Tiziano Ghisu Join Date: May 2009 Posts: 1 Rep Power: 0	Hello everyone, I wastrying to write a UDF defining an adaptive time step function for a time-dependent simulation ... but i encountered problems even before i arrived to the adaptive part, just by using the DEFINE_DELTAT UDF while i was doing this, I encountered a very strange problem. While the simulation is stable for a given time step without the UDF, as soon as i use the udf to set the time step, the simulation blows up, even if i use the same time-step i was using earlier. The UDF I am using is very simple /************************************************ *************** UDF that changes the time step value for a time-dependent solution ********************************************** ******************/ #include "udf.h" DEFINE_DELTAT(mydeltat,d) { real dt=1.0e-4; return dt; } How is this possible? Any suggestions? Thanks Tiziano

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November 25, 2014, 16:58		#2
mahditorabiasr New Member Mahdi Torabi Asr Join Date: Dec 2013 Posts: 10 Rep Power: 12	Too late reply ;) but maybe works for others... The problem is a result of using "Extrapolate Variables" option in calculation menu during adaptive time-step calculation (at least in my case).