how to get the particle residence time in UDF?
 

hello,every one

please tell me how to identify particles injected in different time steps in UDF?

I think the time that particles at the injection can be the sign of identification, but i don't know how to get it in UDF, so i want to get the particle residence time to calculate it, the particle residence time could be shown in the '.part'file, how to get it in UDF? what's the meaning of 'time_of_birth' of particles?

could anyone tell me? thanks in advance!