What exactly is meshing convergence?

Hi friends,
could anyone tell what is meshing convergence?
how do the results of impedance changes, when finer and finer mesh is used?

good question.. i would want to know too
thanks

The idea of a converged mesh is a bit of a misnomer...what you want is a converged result, ie S parameters, Gain, etc. When a result stops changing within a given tolerance from one mesh to another mesh with more density (or higher basis order) it is considered converged. The resulting mesh can be considered a converged mesh though, again, the goal is to converge the result, not the mesh directly. This is especially true since different results can require different meshes to be considered converged...ie S parameters tend to converge more quickly than, say, antenna sidelobe levels...

tallface65 said:

...S parameters tend to converge more quickly than, say, antenna sidelobe levels...

Click to expand...

Hi tallface65,
Thanks for explaining. Could you please elaborate or give some example, So that dummies like me can understand. We are getting S11 parameter for antenna, how to be sure that the S parameters converged, with the provided mesh.

Let say you want to find gain or RL using meshing technique of the problematic volume. This volume initially devided per say 200 parts and solve these 200 small parts either FEM or FDTD etc. You will get one solution after integrating with 200 parts. next we may further divide the same volume in to 300 parts and further integrate the solution with these parts.
The solution with 300 parts may or may not BE SAME as 200 parts case, it depend on the problem and the solution type.
if the solution by 200 and 300 parts is differ by pre-threshold set then solution is not converge and solver will try to further divide the same parts and this time it could be 400 parts.
if solution of 200 parts and 300 parts are closely equal then need not to go for 400 parts right. so now we declare that mesh converged.

hope you understood now

Hi Kspalla,
Thanks very much for crystal clear explanation. one more clarification, is there is any thumb rule or so to select the mesh size.

There are no real rule of thumbs. But some necessary conditions:

1) Make sure that the cell size is smaller than the shortest wavelength of interest (depending on the accuracy you need usually you need cell sizes 10-20 times smaller than the shortest wave length)

2) Make sure that important pieces of your model geometry can be accurately
modelled. Of course 'important' and 'accurately' are not so easy to explain.

Roughly:
important => places you expect the strongest reflections etc
accurately => depends on the geometry but at least you should not short circuit separate wires by choosing too large mesh sizes etc.

But really you have to find out for each model by using smaller and smaller cell sizes until the result seems to get stable.

Hi iyami,
Thanks you people are really good and helpful