CAPE Forum

Ansys => Fluent => Topic started by: infocfd on February 04, 2012, 04:21:53 PM

Title: I am getting divergence on the first iteration for an axisymmetric problem?
Post by: infocfd on February 04, 2012, 04:21:53 PM
I am running a 2d axisymmetric simulation but it diverges on the first iteration with the following message:

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

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

Help me please.
Title: Re: I am getting divergence on the first iteration for an axisymmetric problem?
Post by: william on February 04, 2012, 04:23:32 PM
One reason could be that the geometry is not correct. Do a Mesh->Check to make sure you don't get

Checking for nodes that lie below the x-axis.
WARNING: Invalid axisymmetric mesh: 6 nodes lie below the x-axis.

and
WARNING: Mesh check failed.


For axisymmetric, the axial direction should be x and radial is positive y. Even if the y starts with -1e-32, it will fail.

To fix this:
Use Mesh->Translate and move the geometry so ymin is +ve.