Urgent:buried natural gas pipeline
 

Hello everybody
I'm working on "buried natural gas pipeline" that has a leakage on it,I used following model:
Define-->Models-->Species-->Transport & Reaction
for one of my boundary condition that is pressure outlet,I don't know "species mass fraction" amount of natural gas .
now I have two questions:
1-what is affect of this parameter on solution?
2-if we assume this parameter equal to "zero",will we have true results?

Thanks with regards

1. There is no effect of this parameter on the final solution as long as no back flow is present.

2. You will however during the solution process if backflow occurs having an errenous value of species mass fraction might offset residuals in this area and resulting in severe instabilities.

Dear CFD-Studend
first thank you for your answer
I think backflow occurs in turbulent flowes,but in my work the flow is laminar,so as I can understand from your answer, my assumption is true and it doesn't affect on the final solution,does it?
(I'm working on gas pipeline leakage and our flow is laminar)
with the best regards

hi...
i m also working on the leakage of natural gas in pipelines. I have one question in my problem i get back flow from the inlet after some time of simulation. how can i solve ?

It may because of high pressure loss through pipe line.

thanks for reply.....I know the mechanism but how can i simulate the problem in fluent if there is any tutorial regard this please send....