How to specify an inlet boundary conditions for a fully developed gas flow in a duct.
 

Dear everyone,

My model contains a rectangular duct with various kinds of gases flow through it. What I care is only the fully-developed region while I only know the mass flow rate. I found that if I specify the inlet boundary as a mass-flow-inlet type, the inlet region is not fully developed. So what kind of boundary type should I use in order to avoid the inlet developing length?

Thank you.

Hello,
If you want a fully developed flow at inlet, you should firstly run another simulation, in which you impose periodic conditions or you have a sufficiently long developing region. Once you obtain a developed flow at the outlet of this system, you can write a profile (Write > Profile) for your velocity and then read it in your final case (Read > Profile). When setting boundary conditions, you'll see that this profile will be available ("constant" tab). See FLUENT User's Guide chapter 4.6 for some more details.

I'll have a try and thanks for your help.