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

Mass imbalance in fast chem. reaction

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 12, 2014, 09:41
Default Mass imbalance in fast chem. reaction
  #1
New Member
 
Alexey
Join Date: Jan 2014
Posts: 18
Rep Power: 3
Laexzzz is on a distinguished road
I have a problem with chem.reaction modeling in Fluent (laminar Finite-rate model)

Boundary conditions:

Mixture - 3 species

Mass fraction of I0 = 0.001
Mass fraction of R0 = 0
Mass fraction of M = 0.999

Mixture flows into the tube

Reactions:

I0 -> 2R0
M is not involved into reaction.

After calculation, mass fraction of specie I0 become 0, mass fraction of specie R0 become 0.0015, and mass fraction of M become 0.9985 (so, M turns into R0, BUT M should not react and change own mass fraction).

I tried to use stiff solver, but result is the same.

Any ideas?

I can attach files with solution if it's necessary
Laexzzz is offline   Reply With Quote

Old   March 13, 2014, 02:00
Default
  #2
New Member
 
Alexey
Join Date: Jan 2014
Posts: 18
Rep Power: 3
Laexzzz is on a distinguished road
Also one more problem.

Reaction reaction does not proceed to the end.



But reagent concentration must constantly fall
Laexzzz is offline   Reply With Quote

Old   March 14, 2014, 10:26
Default
  #3
Senior Member
 
François Grégoire
Join Date: Jan 2010
Location: Laval University, Canada
Posts: 366
Rep Power: 8
macfly is on a distinguished road
A numerical solution is not an analytical solution, there is some discrepancy depending on the numerical implementation. You get a discrepancy of 0.05% between the analytical value of Y_M and the numerical value, that's fine with me.
macfly is offline   Reply With Quote

Old   March 17, 2014, 00:19
Default
  #4
New Member
 
Alexey
Join Date: Jan 2014
Posts: 18
Rep Power: 3
Laexzzz is on a distinguished road
Quote:
Originally Posted by macfly View Post
A numerical solution is not an analytical solution, there is some discrepancy depending on the numerical implementation. You get a discrepancy of 0.05% between the analytical value of Y_M and the numerical value, that's fine with me.
Thank you for your response.
What can be done to minimize this error?
Laexzzz 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
Mass imbalance causing no convergenc: domain IS supposed to be positively pressurised kingjewel1 FLUENT 5 April 11, 2012 22:13
Mass imbalance definition Asghari Main CFD Forum 0 January 7, 2007 13:59
define a fast reaction in pre Gab CFX 0 March 9, 2006 17:11
OutletBoundary Condition Causes Mass Imbalance Andy Main CFD Forum 0 March 11, 2004 15:05
Residual Problem -Mass Imbalance Jie FLUENT 0 February 19, 2002 11:49


All times are GMT -4. The time now is 16:07.