Fluent porous media

lostinicem · January 20, 2012, 10:20

Hello community,
as described in the title I've got some problems with porous media diffuser. I try to describe as good as possible and hope for your help

My problem is to create a fluid flow in a porous diffuser; which fluid is now not really important, so I took nitrogen like in tutorial.
So firstly I created a mesh with ICEM: http://img268.imageshack.us/img268/1076/fluent12.jpg
since I'm new to this whole stuff; I think I invested the right amount of time so it should be ok ..
so after that I imported it to fluent:
1) general: I scale it and click on axis-symmetric
2) models: I choose the viscous laminar
3) materials: nitrogen, so I took all datas from tutorial
4) cell zone conditions: I choose nitrogen and click on porous zone; i take also the same inertial and viscous resistance; so I dont use power law model nor do I change the porosity ( its 1)
5) boundary conditions): inlet: I enter here the fluid velocity, since I can calculate it; outlet: I dont touch anything here
6) solution methods: all I change here is the momentum: its on second order upwind
7) monitors: at residuals I change absolute criteria to 1e-6 ( its bigger than in tutorial, I tried to work with the bigger one, but still no convergence); surface monitors: I choose outlet as surface, I also keep the settings from tutorial
8) so at the last step I initialize and compute from inlet, since the tutorial also says so.

So I tried to change and play with the settings but still no convergence, so my velocity profile looks quiet disappionting; and also since I'm new to this stuff maybe I made a stupid mistake?
Hope someone could help me and sorry for my english

lostinicem · January 23, 2012, 04:17

maybe some hints?

SHL · January 25, 2012, 14:40

Hello,

I'm not sure, but maybe you can try to use the ANSYS meshing. Sometimes, incompatibility in mesh causes such problems. Also, you can start calculations with first order upwaind, and then after some degree of convergence, switch to first order.

Hope this works.

lostinicem · January 26, 2012, 11:35

thanks SHL,
but already found the mistake; the problem was in the boundary condition; I didnt defined it as interior.

January 20, 2012, 10:20	Fluent porous media	#1
lostinicem New Member Horst Join Date: Jan 2012 Posts: 19 Rep Power: 14	Hello community, as described in the title I've got some problems with porous media diffuser. I try to describe as good as possible and hope for your help My problem is to create a fluid flow in a porous diffuser; which fluid is now not really important, so I took nitrogen like in tutorial. So firstly I created a mesh with ICEM: http://img268.imageshack.us/img268/1076/fluent12.jpg since I'm new to this whole stuff; I think I invested the right amount of time so it should be ok .. so after that I imported it to fluent: 1) general: I scale it and click on axis-symmetric 2) models: I choose the viscous laminar 3) materials: nitrogen, so I took all datas from tutorial 4) cell zone conditions: I choose nitrogen and click on porous zone; i take also the same inertial and viscous resistance; so I dont use power law model nor do I change the porosity ( its 1) 5) boundary conditions): inlet: I enter here the fluid velocity, since I can calculate it; outlet: I dont touch anything here 6) solution methods: all I change here is the momentum: its on second order upwind 7) monitors: at residuals I change absolute criteria to 1e-6 ( its bigger than in tutorial, I tried to work with the bigger one, but still no convergence); surface monitors: I choose outlet as surface, I also keep the settings from tutorial 8) so at the last step I initialize and compute from inlet, since the tutorial also says so. So I tried to change and play with the settings but still no convergence, so my velocity profile looks quiet disappionting; and also since I'm new to this stuff maybe I made a stupid mistake? Hope someone could help me and sorry for my english

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January 23, 2012, 04:17		#2
lostinicem New Member Horst Join Date: Jan 2012 Posts: 19 Rep Power: 14	maybe some hints?

January 25, 2012, 14:40		#3
SHL New Member Soheil Join Date: Jan 2012 Posts: 1 Rep Power: 0	Hello, I'm not sure, but maybe you can try to use the ANSYS meshing. Sometimes, incompatibility in mesh causes such problems. Also, you can start calculations with first order upwaind, and then after some degree of convergence, switch to first order. Hope this works.

January 26, 2012, 11:35		#4
lostinicem New Member Horst Join Date: Jan 2012 Posts: 19 Rep Power: 14	thanks SHL, but already found the mistake; the problem was in the boundary condition; I didnt defined it as interior.