Posted Thu, 17 Nov 2016 16:22:12 GMT by Lillibrilli1
Dear all,

I hope someone can help me!
I created a 2D model with hydraulic heads at in- and outflow as BC and some wells on the right and the left side of the boundary.
I defined the bottom elevation and the hydraulic heads over the model domain.
The model works finde for confined conditions, so I guess there is no Major error in the System.
The Problem is as follows:
The thickness of the groundwater table is very low (distance between aquifer bottom Elevation and hydraulic head), therefore it is quite hard to reach a steady state.
I think the fluctuations of the hydraulic head related to the thickness of the groundwater layer are proportional high which is why a convergence state cannot be reached.
I tried nearly evrything: Different equation System solver, quasi steady state calculation (transient mode with constant Parameters), refine the mesh in order to decrease the relative big element size related to the thin thickness of the groundwater table, increase residual water depth, setting the Initial conditions (hydraulic head) from a Long transient run and a confined run.
Nothing has worked out, the model will not get into a steady state mode.
What can I do more? Did I Forget something?
I would really appreciate some help !!!
Thank you very much in advance,
Posted Sat, 26 Nov 2016 14:55:20 GMT by Björn Kaiser
Did you use an appropriate error tolerance? The error is normalized by the maximum occurring value of the process variable(s) you are solving. For example, if you have quite low heads, the default error tolerance can be too strict.

If you have reasonable distributions of the process variable(s) and very low imbalances you could check whether or not a less restrictive error tolerance is sufficient.

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