Posted Mon, 08 Nov 2021 08:03:28 GMT by Lin Jimmy
I want to set a radial collector well in FEFLOW7.3.

Like (Lee et. al., 2012), the pictures1's horizontal arm(ex:first arm) will be a MultiLayer well range

So I convert a layer to TetGen mesh.

However, I cannot set MultiLayer well in the zone (Pictures2).
Posted Mon, 08 Nov 2021 10:46:16 GMT by Peter Schätzl Grundwassermodellierer
When having tetrahedral parts in the model domain, you will need to do the selection as a basis for the multi-layer well in a 3D view. I'd probably use discrete features that I set myself plus a well bc rather than multi-layer wells in such a case.
Posted Tue, 09 Nov 2021 16:29:00 GMT by Lin Jimmy
Thanks Peter's reply.

But the "well BC" and "MultiLayer Well" have different physical properties.

I seen the FEFLOW document introduction (

If i didn't misunderstanding, the "well BC" are just points extraction or injection; the "MultiLayer Well" are all the screen interval(top to bottom) extraction?

And in the reality, the radial collector well(like MultiLayer Well) should result in lower drawdown than point well(like well BC).
Posted Wed, 10 Nov 2021 07:32:23 GMT by Peter Schätzl Grundwassermodellierer
Yes, indeed, but even internally in FEFLOW for the simulation run a multi-layer well is a combination of a well bc (on the lowest node) plus a discrete feature representing the well pipe along the screen (only the input/data storage is different). Thus you can mimick a multi-layer well by setting this combination yourself rather than using a multi-layer well. For the Ranney well, you can use a well bc at the bottom of the center shaft, and discrete features for the collector pipes. I'd typically use the Hagen-Poiseuille law (laminar flow) for the collector pipes, and from the FEFLOW book you can figure out what their properties would have to be for a circular pipe with a certain diameter.
Posted Fri, 12 Nov 2021 13:18:58 GMT by Lin Jimmy
Thanks so much, i convert MLW to discrete feature now.

And i set 5 pipes (picture), each pipes use discrete feature property  : [b]source/sink[/b], cross sect.area, hydraulic aperture.

Without Well BC, is this method can approximate radial well?
Posted Mon, 15 Nov 2021 06:33:56 GMT by Peter Schätzl Grundwassermodellierer
Yes, this can be done. You will, however, by setting source/sink define what the discharge from each of the pipes is. By setting a well in the center the discharge is distributed by the model according to acutal pipe lenghtes, flow field, etc.
Posted Tue, 30 Nov 2021 08:42:55 GMT by Lin Jimmy
Dear Peter.

Now i facing "Convergence problem" for steady state.

The picture is the well position(cross section).

radial well 1: red star(elevation : 6-7m), 25,000 CMD
radial well 2: red start(elevation : 2m), 25,000 CMD

Just setting well 1, the simulation can get convergence(balance:1e-5). (however the saturation of elements near well zone approximated '0').

After setting well 1 and well 2, the simulation cannot convergence.

I have try to smooth my mesh, but it cannot solve.

I refer some papers and articles, i know the "Dry cell" will result in convergence problem in unsaturated flow,
but in my case, the well 1 is close to well 2 which cause my elements will be very small(easy to be dry cells).

Any suggestion about simulated convergence problem?

Posted Tue, 30 Nov 2021 14:55:39 GMT by Peter Schätzl Grundwassermodellierer
if the two wells are exactly above each other, you should make sure that in between you have at least one or two extra slices. Otherwise one well will always immediately influence the other one, leading to non-convergence.

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