ANSYS Fluent for transient modelling of fixed mass of gas

[crustaccione]

Hi all, I am extremely new to ANSYS Fluent so pardon me if these questions are very basic. Basically I want to model the flow of a fixed amount of air in a pressurized gas tank throw a pipe and into a chamber using Fluent, how would I go about doing this?

I currently just have the chamber modeled with the inlet set at a certain pressure, but it just doesn't seem like the proper modelling method because the chamber pressure just constantly increases (due to no restrictions on the total mass of the air). Hope someone can help me out.

Thanks!

 

[crustaccione]

*through. I have been reading up a little and I believe it's something to do with mass transfers, but I can't seem to find any tutorials (or at least, my school doesn't have them on the computer) that can help me out.