I am a beginner in C, I need to simulate a fire. Transient solution. A guru (cg) wrote me the below UDF for linearly increasing energy source with time. I need to turn on the fan after two minutes fire starts,how can i do that, any help would be greatly appreciated...

fan BC is just simple constant input. it will make a jump start...i hope it would work.

#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; }

Just add a boolean compare for the calculation to start such as:

if (time >= 2*60)

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

else

{ real source = 0 }

Thank you so much LWoodsend. My question was not clear enough, i meant to turn on the fan at time=120 sec. Fan is simply define by constant pressure jump in BC (Fan BC). Yesterday, i just waited for solution to come up to 30 sec and then i stopped and changed the BC from interior to fan. i just wanna do it fancy way again appreciated ur help, have great weekend!