Posted Sun, 20 Sep 2020 01:48:21 GMT by Felipe Gutiérrez

I have 2 queries related to BCs, both more or less theoretical questions:

1) How does FEFLOW handle the fact of variable elevation at the boundary of a model, when you set a fixed head boundary condition?

It is important for me, because I want to model a big river with Dirichlet BC, but I want to maintain  a reasonable distance (let's say 1-2 [m]) from the elevation of the topography at the boundaries of the model. Is there a way to handle this? maybe by using the 'expression' mode, is there a way to set as a function of elevation?

Something like Head=z(node)-1[m]. Where z(node) is the elevation of a node.

2) In case of modeling this river with third BC (Cauchy), do I have to select two 'rows' of nodes, as shown in the attached picture?, and why the units of Cauchy's formula are given in [m]?

Thanks in advance!
Posted Mon, 21 Sep 2020 05:53:38 GMT by Peter Schätzl Grundwassermodellierer
1) You can do exactly as you wrote. Use an expression with the formula "Elev - 1"
2) Yes, the Cauchy BC needs to cover an area (either horizontal or vertical) - thus you need two rows of nodes on one slice, or you use nodes on two slices (then only a line on each). The value is the reference water level, you need to put a value for the transfer rate in addition (in material properties).
Posted Mon, 21 Sep 2020 14:57:49 GMT by Felipe Gutiérrez

Once again, thanks so much!

Kind regards :)
Posted Tue, 22 Sep 2020 05:47:50 GMT by Peter Schätzl Grundwassermodellierer
Had not seen that your mesh is unstructured - so forget what I said about slices...

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