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

Error: Divergence detected in AMG solver: x-momentum

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 29, 2015, 10:25
Default Error: Divergence detected in AMG solver: x-momentum
  #1
Senior Member
 
Gustavo
Join Date: Jun 2015
Posts: 121
Rep Power: 3
gustavosimiema is on a distinguished road
Hi,

Im trying to simulate the gas (O2 + N2) flow inside a low pressure chamber. In this moment Im not interested in reactions.
Im using steady state, laminar model (Low Pressure boundary slip), activated energy equation and species Transport (inlet Diffusion, Diffusion energy source, Thermal Diffusion enabled).
Operating conditions - 1Pa
inlet (mass-flow-rate) = 4.26e-6
outlet (pressure-outlet) = 0Pa

When I start Simulation the message error appears "Error: Divergence detected in AMG solver: x-momentum" and Im not able to solve it. I tried to reduce the Relaxation factors... but didnt worked.

Anyone has a hint?

thanks in advance
gustavosimiema is offline   Reply With Quote

Old   June 29, 2015, 14:06
Default
  #2
Member
 
Jim
Join Date: May 2015
Posts: 47
Rep Power: 4
CFDYourself is on a distinguished road
try the following:

- don't use mass flow; stick to velcity inlet and pressure outlet. do a back-of-the-envelope calc to find velocity from continuity.
- don't mess with the URFs justnow; stick to the defualt settings.
- don't start with mixtures; start with the defualt air.

keep going more and more simple until it works. also, could be an issue with the mesh. have you named the inlet & outlets etc ?
CFDYourself is offline   Reply With Quote

Old   June 29, 2015, 15:06
Default
  #3
Senior Member
 
Gustavo
Join Date: Jun 2015
Posts: 121
Rep Power: 3
gustavosimiema is on a distinguished road
Thank you so much for your suggestions. I will try it and let you know. Regarding your questionar I named The outlet and outlet. Should I named walls too?
How can I find The velocity from The continuou equation using mass flow rate?
The Knudsen number is 0,038

Thanks
gustavosimiema is offline   Reply With Quote

Old   August 7, 2015, 10:20
Default
  #4
Member
 
Jim
Join Date: May 2015
Posts: 47
Rep Power: 4
CFDYourself is on a distinguished road
Hi gustavo,
sorry, I shouldn't have called it a "continuity equation", the term is ambiguous in this context.

I meant:
Q=rho*u*CSA
mass fr = density * velocity * cross sectional area for flow.

and rearrange for velocity.
CFDYourself is offline   Reply With Quote

Reply

Tags
divergence amg solver

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
divergence detected in AMG solver: momentum sudhakar FLUENT 37 August 29, 2016 20:00
Error: Divergence detected in AMG solver: pressure correction wanna88 FLUENT 19 April 6, 2016 02:57
AMG solver divergence; Mike FLUENT 17 December 14, 2015 14:01
Divergence detected in AMG solver: pressure correction xinquanzhoucn FLUENT 5 July 21, 2014 04:49
Error: Divergence detected in AMG solver: x-momentum/ epsilon/ temperature bubuchacha FLUENT 6 February 26, 2013 04:30


All times are GMT -4. The time now is 08:23.