CFD Online Logo CFD Online URL
Home > Forums > CFX

Flow through porous medium using CFX: lack of convergence

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   February 14, 2011, 12:33
Default Flow through porous medium using CFX: lack of convergence
Senior Member
Join Date: Oct 2010
Location: Zurich
Posts: 176
Rep Power: 6
Chander is on a distinguished road

I am simulating flow through porous medium. In my domain, the fluid enters an inlet duct vertically downwards (-z direction) and impinges on a porous medium vertically , then turns and flows horizontally (y-direction) through porous medium and then at the other end, it again turns upwards (+z direction) and exits through outlet duct. The outlet duct is taken to be long so as to avoid an opening type of boundary condition. Please refer to the attached figure for an explanation of the computational domain.
I am using uniform mesh of equal cell size in x-y-z direction. The porous medium has anisotropic permeability so as to inhibit the flow in x-direction. There is also a small fluid gap above the porous medium.
Now I am not able to get convergence. My inlet Reynold number based on hydraulic diameter for inlet rectangular duct is 3023. Inlet flow is 1 l/min and normal to inlet boundary. I have tried the following:
a) Using a k-omega , and SST model for turbulent flow instead of using laminar model
b) reducing the timescale factor in solver settings so as to under-relax the solution
c)Using a finer mesh

However, I see that the residuals just fail to reduce below certain levels (1e-2 to 1e-3) and thus solution does not converge. Many of the maximum residuals are located near porous-medium-fluid interface. Please suggest a remedy for this issue.
Attached Images
File Type: jpg test_case.jpg (96.1 KB, 102 views)
Chander is offline   Reply With Quote

Old   February 14, 2011, 18:04
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,053
Rep Power: 86
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
A good guide for general tips on convergence is here:

What version of CFX are you using?

There have been some issues with high residuals at the edge of porous regions in past versions, I think more recent versions are improved.
ghorrocks is offline   Reply With Quote

Old   February 15, 2011, 10:16
Senior Member
Join Date: Apr 2009
Posts: 523
Rep Power: 12
stumpy is on a distinguished road
Try the expert parameter:

FLOW: Flow Analysis 1
porous cs discretisation option = 1
stumpy is offline   Reply With Quote

Old   July 23, 2014, 06:32
New Member
shubham jain
Join Date: Dec 2013
Posts: 21
Rep Power: 3
shubham jain is on a distinguished road
hi, i am simulating a Brush seal using Porous medium approach in CFX.

My inlet (INLET) and outlet (OPENING) channels are very long. CFX says that wall is placed at a portion of Inlet, then it stops the simulation.

;My mentor told me to try it with shorter channel length. I tried with shorter inlet and outlet channels and it worked. But i could not understand, why the shortening of channel length makes it (wall places at INLET) better??

Picture attached: Green region in right is inlet.... Dark yellow in the middle is the porous medium ..... light yellow in the left is outlet

Thanks in advance
Attached Images
File Type: jpg geom_1.jpg (6.8 KB, 15 views)
File Type: jpg geom_1_3D.jpg (13.7 KB, 12 views)
shubham jain is offline   Reply With Quote


cfx, lack of convergence, porous medium, porous-fluid interface

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mass flow and U-Mom flow in CFX Zhihua Xie CFX 0 September 3, 2007 09:49
3D Fluid Flow Convergence problem Emily FLUENT 2 March 21, 2007 23:18
Turbulent flow through porous medium? Shankar FLUENT 3 September 26, 2002 15:46
gas flow through porous medium Shankar FLUENT 0 February 18, 2002 22:18
fluid flow fundas ram Main CFD Forum 5 June 17, 2000 21:31

All times are GMT -4. The time now is 03:37.