Hi all: I am modelling a fire and I have a volumetric heat source inreasing linerly with time upto 15th minute where released heat rate is 5 MW. I have never written a PDF before and i am a beginner in C. So your advices would be appreciated. -Matt

As most other users will tell you, you got to read the manual.

Use the UDF that defines a profile. You can put a check for the flow time and when the logic is true it will stop increasing the temperature.

or you could use...

#include "udf.h"

DEFINE_SOURCE(energy_source,c,t,dS,eqn) {

real time = CURRENT_TIME;

real source = 100. * time; /* units of Watts/m3 */

dS[eqn] = 0.;

return source; }

thank you much Phil and cg, appreciated..