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-   -   Error on Global Courant Number during 'calculation' (http://www.cfd-online.com/Forums/ansys/116247-error-global-courant-number-during-calculation.html)

Bin April 16, 2013 01:06

Error on Global Courant Number during 'calculation'
 
Hi all,

I encounter an error stating that:
"Error: Global courant number is greater than 250.00 The
velocity field is probably diverging. Please check the solution
and reduce the time-step if necessary."


I had reduced the time-step as recommended by the software, it performs good in 1st few seconds. After that, this message pops out again.

May I ask what possible factors that cause this error and how can i solve it?

Thanks alot for the helps.

Regards
Bin

oewnce932c April 16, 2013 07:12

write some data about your simulation. velocity, grid size and time step.
for time step check this thread http://www.cfd-online.com/Forums/cfx...step-mean.html
may be using step-function after some iteration will help your.

dklastiwka April 20, 2013 10:18

What kind of simulation are you doing? We need more information before recommending some solutions.

Bin April 20, 2013 21:12

I'm doing simulation on horizontal distillation column. I'm new to ANSYS so at this moment I'm just trying to set up FLEUNT to check whether the model can be run. Here is my setting

Model:
multiphase: VOF
enery equation: on
Species: Transport Species
Material:
Mixture of ethane+water
Phase:
phase1 - air
phase2 - water+ethane mixture
Boundary condition:
Inlet: mixture tab ~ velocity-inlet with 0.15m/s v at 300K
phase 2 tab ~ volume fraction 1
all outlets: default pressure outlet
bottom wall: 370K (To separate ethane from water, not sure the number is
correct or not)
Solution Initialization:
compute from inlet, all the values are in default

Sometime I will get other errors instead of courant number, like AMG solver: temperature or pressure. Is this settings correct? Sry if my setting is a total mess, I'm new to the software ==". And what settings cause the errors??


Thank you for all the helps, seniors.

Regards
Bin

dklastiwka April 23, 2013 00:02

What is the phase mixture at the inlet? Is this a transient or steady state run?

Bin April 25, 2013 06:03

Quote:

Originally Posted by dklastiwka (Post 422471)
What is the phase mixture at the inlet? Is this a transient or steady state run?

First of all, thanks for the reply.

I'm using steady at this moment. Is the overall settings reasonable? Since I cant found any tutorial that directly teach about modelling distillation column, I had tried to adopt the settings that I think is related to my project and apply it.

Do you have any suggested websites, guides, pdf or etc as references to this project? I need it desperately. I had try to search on web for weeks, but I cant get anything close. I'm currently reading the user guide and tutorial guide to find some clues.

Thank you for the replies and helps

Regards,
Bin


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