Error: Divergence detected in AMG solver: xmomentum
I am doing air injection on water using VOF model with axisymmetric condition. But when i start the calculation it gives me this error
:( Error: Divergence detected in AMG solver: xmomentum Please can anyone help Thanks in advance Regards, Smaras 
Reduce the under relaxation factors

Quote:
Already done that....but still the same problem. Is it something related to axial or radial direction as i am doing axisymmetric VOF? Thanks in advance. 
Hi Smaras,
Does it run for a few iterations before getting this error? If you are running 2Daxi, are the mesh checks ok? have you set your domain in the XY plane, only positive Y and defined the axis (if you have nodes on Y=0)? Marion. 
Quote:
Daniele 
Quote:
Thanks everyone 
Quote:
is taking x axis as axisymmetric needed in 3D too??? 
Try to change the size mesh and if you are employing a tetrahedral mesh change to hexahedral

Quote:
but it,s not possible for my geometry to use hexahedral:( 
Change the mesh, time step or relaxation factors

Quote:
but i tried a lot but i coudnt make my mesh better(using gambit) and i,m using steady solver. i reduced the relaxation factors too but it didn,t work. i,m sure that problem is related to my periodic boundaries.but i don't know what is the problem and what to change about them:confused: 
Quote:
Can you post your domain/BCs and describe your problem more? OJ 
Quote:
i found that the problem was in one of my walls.i set its coroct boundary and it is working now:D 
Error: Divergence detected in AMG solver: xmomentum
Hello,
I have the same problem though! For my problem, I am defining most of the boundary conditions (like inlet velocity, turbulence boundary conditions) with UDF file which is successfully interpreted into the Fluent. However, the solution is not converging and the error of "Divergence detected in AMG solver: xmomentum" is showing up. I have reduced the under relaxation factors to almost 2 order of magnitude for pressure & momentum+ changed the numerical scheme as well as the descretization order+ lowered the initial guess value for the velocity+ converted the tetrahedral cells to hexahedral one BUT still the divergence error appears without any iterations!! nevertheless, after lowering the initial velocity value, the case run for few iterations (less than 15) then again the error came on the screen :( So, I have gone through many ways to solve this problem and now have no more idea. I will really appreciate to hear some suggestion/help from you forum people as I am stuck on my project. Thank you in advance 
Does your simulation run if you use (reasonable) constant values at the boundary conditions instead of the UDFs?

Thank you dear Alex.
After what you have asked I have tried to (one by one) replace the UDF with the a constant value wherever necessary in order to find out the problem. Finally, I've noticed that there is something wrong with the UDF that defines a resistance profile in the porous zones. However, I was not able to figure it out what causes the problem! Any idea now?? 
You could try to figure it out by yourself, or you could post the UDF here along with all relevant information and see if someone can help.

Quote:
my problem was related to the periodic boundaries.after changing some things in gambit ;i had solved my problem.if your problem has periodic boundaries i,ll explan it in details for you. 
AMG solver divergence
Quote:
My geometry is sym about Y axis, i am giving it sym. But i am getting AMG solver divergence X momentum. I tried changing URF. Also it dont run for even 1 iteration. Can you suggest me the way. https://www.dropbox.com/sh/udmvmhbiaxsjrl1/Dd9RRnu7OI thanks 
Quote:
Daniele 
All times are GMT 4. The time now is 02:46. 