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-   -   AMG solver and floating point divergence (http://www.cfd-online.com/Forums/fluent/104721-amg-solver-floating-point-divergence.html)

ndabir July 13, 2012 14:21

AMG solver and floating point divergence
 
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Hi,

I am modeling bubble collapse close to wall. when I use the 2d plane simulation, the simulation starts for a while and continues until at later iterations, it diverges. But when I change the setting to 2d axisymmetric, it gives this error at the first iteration:


Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: temperature
Primitive Error at Node 0: floating point exception

any idea what is the problem? do you think the mesh has a problem? why does it works for plane simulation but does not work for axisymmetric? attached is a picture of pressure contours after the first iteration which the solution diverges. the blue parts correspond to 1 Pa!

ndabir July 13, 2012 17:20

I think I found what was my problem. the axial and radial directions were opposite. which means, I guess fluent only accepts geometries which their axis of axisymmetry, is lied on typical "x-axis" not "y-axis". previously, the axis of axisymmetry in my case was on the "y-axis". I simply change it on to "x-axis" and now the simulation is working. hope it doesn't diverge late.


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