CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

Formation of oxide

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 29, 2012, 10:41
Red face Formation of oxide
  #1
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
Hello, gays, I wonder if I can simulate the formation of oxide in a tube flowing water saturated with oxygen, and how could you do this, since the oxide is a solid material.
If not.
How do I implement a thickness for the oxide, in the pipeline to set boundary conditions for diffusion of oxygen in the oxide that are different from the fluid.
cmageski is offline   Reply With Quote

Old   July 1, 2012, 08:32
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,823
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
How does the oxide form? Does oxygen react with gas/liquid and precipitate out or does it react with the vessel wall and form an oxide skin?

And what do you want to model with this chemistry? The surface roughening? Or the wall thinning? Or the fluid domain getting choked with oxide? Or just how thick the oxide becomes?
ghorrocks is offline   Reply With Quote

Old   July 2, 2012, 08:21
Default
  #3
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
It react with the vessel wall and form an oxide skin.
I want the concentration oxigen on the surface this oxide and the thickness of it after a certain time. In order to predict the corrosion rate this pipe.
cmageski is offline   Reply With Quote

Old   July 2, 2012, 08:39
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,823
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
CFX can model all the basic physics and chemistry in this process, you just need to specify it. What information do you have about corrosion rate versus oxygen concentration, and any other parameters (eg corrosion rate versus depth of existing oxide)?
ghorrocks is offline   Reply With Quote

Old   July 2, 2012, 09:25
Default
  #5
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
I have an equation that depends on the concentration of oxygen, and I need os concentration in the first node near the wall. although with the formation of oxide position of the node and concentration also changes. In susface of the oxide the velocity is zero, but the concentration not. What I export of the CFX is a concentration of oxygen carried by water through the additional variable in developed turbulent flow at the entrance. But to provide the formation of the oxide I'm not getting.

Please help me!
cmageski is offline   Reply With Quote

Old   July 2, 2012, 19:09
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,823
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Do you have a model for how the existing oxide affects new oxide formation?

I suspect you will need an AV to track the oxide thickness. Ideally this would be an AV on the wall only but I cannot see how to implement that so it will probably have to be a field AV, but one which you only define values at the wall.
ghorrocks is offline   Reply With Quote

Old   July 3, 2012, 07:46
Default
  #7
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
But you know how can I todo this? Do you have more information about this field AV?
cmageski is offline   Reply With Quote

Old   July 3, 2012, 07:53
Default
  #8
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
Sorry I forgot to answer first question. I don't have a model, but of the oxide only is formed. It don't exist before and after of formed it don't affect new oxide formation.
cmageski is offline   Reply With Quote

Old   July 3, 2012, 18:59
Default
  #9
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,823
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
The tutorials have some examples of AVs (I think).

Sounds like a simple case of integrating the oxygen concentration over time then. But unfortunately this is tricky to implement in CFX - you can either do it in fortran, or use a sneaky trick to allow you to access the value of an AV in the previous time step (search the forum for TRANS_LOOP and I think you will find it).
ghorrocks is offline   Reply With Quote

Old   July 24, 2012, 13:09
Default Problem in pressure
  #10
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
I have a problem with transport in turbulent flow of additional variable where the pressure grows and stabilizes above the speed which means that there is no convergence problem.
What type of solution is the outlet pressure of 1 atm.
The geometry is a pipe with contraction and expansion.
Please help me.
cmageski is offline   Reply With Quote

Old   July 24, 2012, 20:56
Default
  #11
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,823
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Can you post this as a new thread? No need to hijack other threads.
ghorrocks is offline   Reply With Quote

Old   July 25, 2012, 13:28
Default
  #12
New Member
 
Cecília Mageski
Join Date: Sep 2011
Posts: 16
Rep Power: 5
cmageski is on a distinguished road
Yes I did this. When I realized I was posting here it was late.
cmageski is offline   Reply With Quote

Reply

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
Ice Particle formation using CFX Dinesh CFX 1 April 7, 2010 17:39
FLuent Sulphur formation jehuty FLUENT 1 April 14, 2009 03:07
VOF and Droplet Formation saang CD-adapco 1 June 7, 2005 03:59
NOx Formation in Turbulent hydrogen combustion Ali Yigit FLUENT 1 December 22, 2003 04:50
SOx formation olivier Main CFD Forum 0 December 18, 2001 13:27


All times are GMT -4. The time now is 10:14.