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

legendyxg · May 11, 2010, 05:08

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.

leonardo.morita · May 11, 2010, 06:30

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.

legendyxg · May 11, 2010, 08:32

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

May 11, 2010, 05:08	How to specify an inlet boundary conditions for a fully developed gas flow in a duct.	#1
legendyxg New Member Yang Xiaoguang Join Date: Apr 2009 Posts: 24 Rep Power: 17	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. CFD_beginner12 likes this.

May 11, 2010, 06:30		#2
leonardo.morita Member Leonardo Giampani Morita Join Date: Apr 2009 Location: Paris, France Posts: 58 Rep Power: 17	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. CFD_beginner12 likes this.

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May 11, 2010, 08:32		#3
legendyxg New Member Yang Xiaoguang Join Date: Apr 2009 Posts: 24 Rep Power: 17	I'll have a try and thanks for your help.