CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

How to stop diffusion and advection in a zone for selected species.

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

LinkBack Thread Tools Search this Thread Display Modes
Old   March 18, 2012, 23:59
Unhappy How to stop diffusion and advection in a zone for selected species.
New Member
Join Date: Jan 2012
Posts: 4
Rep Power: 0
hda is on a distinguished road
I have a microchannel partitioned in two sections with a perforated membrane of a finite thickness. A dilute mixture of oxygen, glucose and water is given from inlet.

The mixture can flow through the perforation as it is. In addition, there is molecular diffusion (but no advection) through the membrane solid. I want to make the membrane allow diffusion of water and oxygen but not of glucose.

How can we model this?

Here is what I tried but it did not work:
1) Set the membrane and both of the sections to be fluid zones of "mixture" material.
2) Set the velocity components in the membrane to zero using "fixed values" tab. This will stop advection.
3) Using a UDF, set the mass diffusion coefficient of glucose inside the membrane zone to a very small number, say 1e-20 (setting it to zero gives a warning). However, set the coefficients of oxygen and water to their appropriate values. This will stop diffusion of glucose while allowing oxygen and water to diffuse.

Outside the membrane zone all species have appropriate values for their mass diffusion coefficients (order of 1e-10).

Unfortunately, when I run this, I see glucose diffuse right into the membrane. Setting its mass diffusion coefficient exactly to zero (despite the warning) won't help.

It seems like UDF works fine because I see in the contour plot whatever value I assign for diffusion coefficient of glucose in the membrane. Fixed values for velocities also work, since the contour plots show zero velocity inside the membrane.

I thought that this trick would stop the diffusion and advection mechanisms for glucose in the membrane but it did not work.

Any ideas why did this fail?

Last edited by hda; March 19, 2012 at 16:32. Reason: grammar
hda is offline   Reply With Quote


advection, convection, diffusion coefficient, zone, zone specific

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
multiple species diffusion sosat1012 ANSYS 2 November 23, 2011 11:48
convection, diffusion, advection, dispersion Lam Main CFD Forum 7 May 18, 2007 12:04
convection, diffusion, dispertion, advection ? vijesh joshi Main CFD Forum 14 March 17, 2006 23:20
2D advection - diffusion Radu Main CFD Forum 1 September 28, 2004 03:47
Advection - diffusion??? Amanda FLUENT 0 January 29, 2002 20:26

All times are GMT -4. The time now is 19:13.