[esi1520]

Hi,

I have two mixture in fluent model for two different zones.
In fluent manual emphasize when user add mixture component the last species automatically disappear in BC species list, Initialization tab and other sections.

I have a big problem!!!

For example in mixture species, N2 selected as last component. N2 attend only in 1 zone. I set only flow model and check continuity. after some iterations, result report shows that N2 with high mass fraction attend in two zone.


How to set fluent model to define N2 is for "only" 1 zone and fix continuity problem?

Thanks a lot

Please help me...

[Светлана]

Why is N2 only present in one zone and not in another? If there is a barrier which prevents entrainment of N2 from one zone into another, have you defined an interface between these two zones?

[esi1520]

Originally Posted by Светлана

Why is N2 only present in one zone and not in another? If there is a barrier which prevents entrainment of N2 from one zone into another, have you defined an interface between these two zones?

Thanks for your reply,

In my geometry and model there is 2 zone like shell and tube that exchange energy from shell wall to tube. Each zone have mixtures of species. Nitrogen (N2) only present in shell but after some iteration, mass fraction of N2 in tube section reach a number around 0.7 while because of physical model i expect mass fraction of N2 be zero.

Also after initialize, fluent automatically set 0.01 for mass fraction of species and value "1-sum of species" for last species in list. I think this initial mass fraction cause to continuity problem.

Another problem in this post is that last species of mixture list disappear in BC, under-relax factor and ...

How can i resolve this problem?

Thanks a lot

[Zigec]

I had some similar problems with the convergence, I had the continuity between 0 and 1... I tried with up to 40 inner iterations and under-relax for all other species 0.3 and lower the u-r also for pressure. This solved my problem with the convergence. It was after that e-4.

Regarding that N2.. I have some similar problems with the ST model. If you find a solution to this, please post it in the forum.

[esi1520]

Originally Posted by Zigec

I had some similar problems with the convergence, I had the continuity between 0 and 1... I tried with up to 40 inner iterations and under-relax for all other species 0.3 and lower the u-r also for pressure. This solved my problem with the convergence. It was after that e-4.

Regarding that N2.. I have some similar problems with the ST model. If you find a solution to this, please post it in the forum.

Dear Ziga,
Thanks for reply and advice

I will try again with your suggestion. What is 'inner iterations" and how can i set these in fluent?
Also i cann't understand "lower the u-r also for pressure" in your post?
Please help me again?

When i found a way to solve problem of N2, i send u a message in private

Tjanks again

[Zigec]

u-r, i shortened under-relaxation. I have for pressure 0.3, the same for species.

Solving tab/Advanced... and set Max Iterations to 40.

[esi1520]

Originally Posted by Zigec

u-r, i shortened under-relaxation. I have for pressure 0.3, the same for species.

Solving tab/Advanced... and set Max Iterations to 40.

Ok I've got it!!!

Is in your simulation u have "reverse flow" problem?

Thank you very much....

[Zigec]

First I had the reverse flow problem. I changed the geometry so that outlets have been further away from the inlet, that solved my problem ..