Increase in reactant concentration

Jenny_W · September 17, 2012, 08:09

Hi Everyone,
I am simulating a reaction in FLUENT. There are 2 reactants and 2 products.
I wrote my own reaction mechanism and it seemed right.
However, when I checked the results, the concentration of one of my reactants increased towards the exit of my computational domain.
This is very confusing because I think that the amount of reactants should reduce as they are converted to the products.
If anyone has faced this problem before or knows what may have gone wrong, please kindly let me know.
Thank you,
Jenny

eng_s_sadeghi · September 17, 2012, 08:52

That may be the reverse flow at outlet. You have not set outlet fuel mass fraction as zero and when it reverses, cames back to domain.

snh · September 18, 2012, 03:36

Quote:

Originally Posted by eng_s_sadeghi

That may be the reverse flow at outlet. You have not set outlet fuel mass fraction as zero and when it reverses, cames back to domain.

Hi,
how to set the outlet fuel mass fraction to zero ?

eng_s_sadeghi · September 18, 2012, 04:17

Quote:

Originally Posted by snh

Hi,
how to set the outlet fuel mass fraction to zero ?

Outlet should be as "pressure outlet" to could set the species parameters.

Jenny_Wong · September 18, 2012, 11:59

Thank you very much eng_s_sadeghi, I will try it.
Jenny

September 17, 2012, 08:09	Increase in reactant concentration	#1
Jenny_W Member Jenny Join Date: Apr 2011 Posts: 34 Rep Power: 15	Hi Everyone, I am simulating a reaction in FLUENT. There are 2 reactants and 2 products. I wrote my own reaction mechanism and it seemed right. However, when I checked the results, the concentration of one of my reactants increased towards the exit of my computational domain. This is very confusing because I think that the amount of reactants should reduce as they are converted to the products. If anyone has faced this problem before or knows what may have gone wrong, please kindly let me know. Thank you, Jenny

September 17, 2012, 08:52		#2
eng_s_sadeghi Member Join Date: Mar 2011 Posts: 64 Rep Power: 15	That may be the reverse flow at outlet. You have not set outlet fuel mass fraction as zero and when it reverses, cames back to domain. Jenny_Wong likes this. __________________ Saeed Sadeghi Ansys Fluent CFD Consultant

September 18, 2012, 11:59		#5
Jenny_Wong New Member Jenny Join Date: Jan 2012 Posts: 11 Rep Power: 14	Thank you very much eng_s_sadeghi, I will try it. Jenny eng_s_sadeghi likes this.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Reaction with zero reactant..	hard33psingh@gmail.com	FLUENT	0	January 21, 2010 05:43
How can I increase Heat Transfer at Domain Interf?	B.Simon	CFX	3	October 28, 2008 19:53
Concentration Scale Data Interpretation	usker	Siemens	4	October 23, 2007 21:30
negative species concentration again	Andrew Garrard	FLUENT	0	March 22, 2005 12:36
initial concentration in multicomponent mixtures	isidro	Siemens	0	April 26, 2004 08:40