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-   -   divergence detected in AMG solver: momentum (https://www.cfd-online.com/Forums/fluent/43285-divergence-detected-amg-solver-momentum.html)

sudhakar January 10, 2007 00:36

divergence detected in AMG solver: momentum
 
Hello Friends, i am working on shell and tube heat exchanger using seggregated solver and laminar,and alsoheat exchanger models My simulation today give me an error message:"Divergence detected in AMG solver:x momentum Error object:()

I have no idea what it means and how to get around it.

I like to be helped by members of the forum.

With advanced thanks

sudhakar

Wang January 10, 2007 12:42

Re: divergence detected in AMG solver: momentum
 
I have same problem.

KP January 10, 2007 13:02

Re: divergence detected in AMG solver: momentum
 
Tighten your under relaxation factors and then run. For instnace check on momemtum under relaxation factors now say its 0.5 tighten it to 0.1. Then this error should go away. However doing this increase your tun time. KP

sudhakar January 11, 2007 05:53

Re: divergence detected in AMG solver: momentum
 
I tried from urf from .7 to .001 .but i could not get. in my problem no of cells are more than 8 lakh. my problem is shell and tube heat exchanger in 3 dimensional using seggregated solver.previous i solved same problem with out headers .but now i inserted headers now i got above problem divergence detected in AMG solver: momentum

please help me to solve this problem

Wang January 12, 2007 07:56

Re: divergence detected in AMG solver: momentum
 
Hi,

I used coupled solver instead of seggregated one. Then reduced urf. The case is working.


almostafa67 August 7, 2010 05:26

divergance
 
hi everybody...
i have same problem,i changed urf from 0.5 to 0.05 but again error message showed up!
dear wang i did not understand ur method please explain more and help me out.
thank u in advance for any help provided:)

mrnsmith May 5, 2011 18:14

So by coupled I think he means under the solutions methods tab and under Pressure-Velocity coupling Scheme to change it to coupled. And then urf means Under relaxation Factors in the solution controls tab.

However I am having the same divergence in x-momentum error and this isnt working either!

zeybi1604 March 11, 2012 16:25

Hello. i am doing a multiphase simulation in a packed bed using the mixture model. the volume fraction used was 0.5316.i keep getting the error message "divergence detected in AMG solver: x-momentum" for all the different solvers used and i even changed the under relaxation factors. i really have no idea how to proceed with this simulation!plzz help!thank u.

zfa91 July 1, 2013 03:27

mine too
 
Dear friends,

I'm having same problem , as i ve checked the meshing was ok. but, x-axis still not 0. how to state the axis as needed plus how you re sure your boundary condition is correct?

This x-momentum problem make me stuck forever.

Help me

zeybi1604 July 11, 2013 01:04

to check whether your boundary conditions are properly defined just have a look at your values obtained from the velocity vector profiles.you should generally have an idea where should be the inflow or outflow this can also help you to check your suitable conditions.

which version of fluent are you using?

i got this proble because i was using an old version of fluent.maybe you should update yours.

my problem on the x-momentum was never solved.

try the different relaxation factors and your conditions setings.

goodluck!

ashok September 21, 2013 10:40

Solution for Error : Divergence detected in AMG solver: x-momentum
 
This error is due to large mesh element size. If the mesh was created in units other than metre the mesh has to be scaled. Go to problem setup/general/mesh/scale and check on the specify scaling factors.

Volumeoffluid November 28, 2013 10:17

Hi all,
i have this error...

# Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!

Error: Divergence detected in AMG solver: x-momentum
Error Object: #f

May i must increase from the solution controls---advanced---max fine relaxation ????
What shall i do??
Thank you in advance!

ashraf88 November 28, 2013 11:34

Hi, I had the same problem before,

1. check your mesh, make finer
2. check the initial conditions, usually this kind of errors appears because of wrong values of the initial conditions
3. good luck

Volumeoffluid November 29, 2013 06:44

Quote:

Originally Posted by ashraf88 (Post 463921)
Hi, I had the same problem before,

1. check your mesh, make finer
2. check the initial conditions, usually this kind of errors appears because of wrong values of the initial conditions
3. good luck

Hi dude,

I have still the same problem...Maybe i should chande the under relaxation factors and scale better the mesh...pfff..

ashraf88 November 29, 2013 14:45

Quote:

Originally Posted by Volumeoffluid (Post 464007)
Hi dude,

I have still the same problem...Maybe i should chande the under relaxation factors and scale better the mesh...pfff..

try to make the energy under relaxation factor 0.995
I am sure that eventually you will solve the problem.

good luck

Zaktatir November 30, 2013 09:13

the reason of the divergence is manifold: without any setting you get only speculative tips nothing more! Either you post your settings or you contact you Ansys support if you have a legal license.

-Boundary Conditions
-Velocity Profiles
-Numerical Setup

The fact that you give small URS til 0,001 and we still get failure that means your setup is wrong

Volumeoffluid December 3, 2013 11:12

Quote:

Originally Posted by Zaktatir (Post 464148)
the reason of the divergence is manifold: without any setting you get only speculative tips nothing more! Either you post your settings or you contact you Ansys support if you have a legal license.

-Boundary Conditions
-Velocity Profiles
-Numerical Setup

The fact that you give small URS til 0,001 and we still get failure that means your setup is wrong

Hi Zaktatir,
so do you want to send you my settings-project to take a look?
My email is jimromanas@hotmail.com
Thank you in advance!

sachin07essence December 16, 2013 01:29

same problem is there with me

mahditorabiasr January 12, 2014 17:28

Minor problem in geometry
 
Any minor problem in geometry also can lead to such a error.


In my case, I used DesignModeler and I got following warning after using FaceSplit tool between modeling.

"Warning: At least one tool geometry selection did not result in a split"


Although the Model status was Ready(but in yellow color!!) and I jumped to Setup, that error returned.

samir_cfd March 28, 2014 11:00

Good day
I have a problem when I am simulate unsteady flow around a propeller, divergence detected in amg solver. x momentum, I reduce the URF but is the same problem


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