Björn Kaiser

Perl, in 3D models source/sink relates to the volume of an element, it can typically not be used for the description of groundwater recharge. In/out flow on top/bottom is an area related property [e.g. mm/a=l/(m²*a)] which can be applied to describe the net infiltration into the model area from the top.

Sergiy, 1D Discrete Features consist of geometries either of type Join Edges or of type Slice Edges. Accordingly you need to select either Join Edges or Slice Edges in the Selection toolbar. If you have a selection active please go to the Data Panel, right click on Discrete Features and add a Discrete Feature.

[b]1) In general, how do I know when warnings about convergence are something to be concerned about? Should I always expect model results to be unacceptable if I get a convergence warning?[/b]
In principle I always would critically inspect the results with regard to numerical artefacts and I always would try to improve the model to reach convergent computational findings.

[b]2) Why is there a warning at "time:  1.000000e-03" if this is a steady-state model? (I wouldn't expect time to be a meaningful descriptor in this case.)[/b]
You are more than right. “Time” is not a meaningful descriptor. The word may be rather considered as a dummy-time, which has been introduced in times when FEFLOW was born. Since then the word “time” has been changed to a more descriptive word, because the difference between steady-state and transient is clear.

[b]3) What changes could be made to this model (or a model in general) to fix the convergence problem?[/b]
One option is to switch from steady-state to transient by keeping the boundary conditions and material properties constant. In this way you allow the system to evolve through time to reach a steady-state solution. Another option is to increase the residual water depth for unconfined layers in the Problem Settings. Please note that this option may introduce an artificial wetting of the “unsaturated zone” to archive numerical stable computations. Given the fact that the system is very dry, I suggest to solve the Richards equation instead of Darcy.

Hi Zeno, to mimic a BHE by means of a Heat nodal sink/source BC you may use a highly conductive 1D Discrete Feature (DF) and distribute Heat nodal sink/source BC’s evenly along the DF. The crucial disadvantage is given by the fact that you have to know a priori the charge/withdrawal, while for BHE’s you may use for instance a temperature differential. Usually vertical axisymmetric models are used for fully discretizing the geometry of the BHE within the finite element mesh.

If you like to model a BHE in a 2D vertical axysimmetric projection I assume you want to investigate local rather than regional effects. In this context, I recommend to fully discretize the geometry of the BHE in the mesh.

All material properties related with sources/sinks (e.g. in/outflow on top/bottom, source/sinks for fluid, heat and mass) may be manipulated by parameter expressions. If you want modify other parameters you need to develop your own plugin as already stated by Blair.

Hi Zeno, yes the plugin works for FEFLOW 6.2. The plugin uses callback functions related with the simulation. Accordingly, you only have to attach the plugin to the fem-problem and run the simulation. You may even check the impact of varying the thermal conductivity according to temperatures. Run the exactly the same model two times, one time with and one time without the plugin.

Hi Ramón,

The predefined distribution Error Norm Heat works fine using the latest patch. Could you please update to the latest patch and try to reproduce your observation again?

Please click on Help in the FEFLOW menu, then on about. Finally, “check for updates”

There are two possible reasons.

The first reason is that you are in demo mode and you try to open a model created on another PC which exceeds the number of nodes, while the model created on your PC is lower than the limitation. In demo mode the limitation is given by 500 nodes per slices with a maximum number of 5 slices.

The other reason is that you do not have a cooperate license, but you try to open two models at the same time.