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

I have same problem.

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

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

Hi,

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

[almostafa67]

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]

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]

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]

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]

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]

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]

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]

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]

Originally Posted by ashraf88

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]

Originally Posted by Volumeoffluid

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]

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]

Originally Posted by Zaktatir

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]

same problem is there with me

[mahditorabiasr]

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]

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