Lin Jimmy

#Case target
In my case need to set 2 radial wells.

A radial well have 10 pipes, each pipes should extract 5,000 CMD.

Then a radial well will extract 50,000 CMD.

2 radial wells will extract 100,000 CMD.

#My model
1. Unsaturated flow (Richard's), the well zone van Genuchten parameters is: (alpha=14.5, n=2.68, sr=0.045).

2. One aquifer and one aquitard.

3. Set radial well by discrete feature with well BC

#Problem
I just set the first radial well (50,000CMD), then get non-convergence.

I have try to smooth mesh but not work.

According to the reference: https://www.waterloohydrogeologic.com/2017/10/20/experiencing-non-convergence-error-here-are-some-tips/, I consider the dry cell is the reason that result in non-convergence.

If the well location (elevation) cannot adjust(layer thickness fixed), how can i solve the convergence problem?

*The detail setting and result as shown in picture.

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?

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?

Thanks Peter's reply.

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

I seen the FEFLOW document introduction (http://www.feflow.info/html/help73/feflow/09_Parameters/Boundary_Conditions/Flow/multilayer_well.html).

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).

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).

Thanks you so much.

I took your reference.

And i specially adjust the layer thickness of negative recharge zone, that can avoid the water below the zone.

And this solve the convergence problem.

TO: Durchlassigkeitsbeiwert

Thanks your explain.

Why the recharge in gravel only can work when area below water table?

I'm run a richard's case.

And my condition involve recharge(some >=0； some <0).    [b](* ps: Because this area didn't have enough well data, so the negative recharge is replace well) [/b]

And my richard's parameters are following :

Property            Sr        alpha      n
Gravel              0.0349  5.79  2.2355
Sand                0.045  14.5  2.68
Clay                0.068    0.8  1.09

Actually i'm not sure the gravel parameters(right/wrong?)
(reference:https://www.researchgate.net/publication/270118948_Evaluation_of_Hydraulic_Parameters_Obtained_by_Different_Measurement_Methods_for_Heterogeneous_Gravel_Soil)

[b]My problem is :

I set two layer for this case(aquifer, aquitard), and get convergence result.

However I discrete first layer to 10 layer(parameter be the same), get a result that no convergence(very high head).[/b]

Is my richard's parameters set wrong?

In my comprehension, the higher 'alpha' will cause water drain easy, so the recharge water will easy to drain to aquitard layer which numerical simulation easy divergence part,
therefore I try to let all layer 'alpha' be 0.0008, and get convergence. But it's very unreasonable.

thanks

The first time to do this case.

And i confused why i set the final simulation time(3650 days), but the particle trace time will come to '166371'(bigger than my simulation time).

Thanks!

Hi bgourley!

Thanks u tell me add layers in FEFLOW, it help me to save lots of time .(I always add layers by coding, it need to export and import elevation data).

And the table reference:
https://www.researchgate.net/figure/1-Van-Genuchten-parameters-and-saturated-hydraulic-conductivity-K-s-for-soil-layers_tbl13_256546124

And Durchlassigkeitsbeiwert!

Thanks u so much, you help me more understand van genuchten parameters!

I think i need to look more article about unsaturated simulation and van genuchten model.

And my case is part of GWF.

Jimmy