change a certain input boundary condition to a different material in FLUENT 6
 

May I clarify, is it possible for us to change a certain velocity input boundary condition to a different material (chemical tracer) in FLUENT 6? Or must we use other methods such as injections? Correct me if I am wrong but i.e. in FLUENT 12 I remember I can do that.

I need to input a pulse input into a rectangle tank to measure the velocity decay of the tracer. What would be the easiest way to do that?

Any help is greatly appreciated.

Haze