Thomas O.

Pete,

sorry for this really late reply. And thanks for replying to my post BTW. Agreed that transient help getting a better feeling of the situation. In this case, considering other sources of uncertainty, I wonder if the extra work is worth the effort of implementing everything in a numerical model and doing simulations with very short time steps...

Thomas

Hi everyone,
we're often using FEFLOW to estimate groundwater inflow and drawdown related to excavations in fractured bedrock (eg.: tunnels). To do so, we use hydraulic conductivity values obtained from packer tests and/or long duration pump tests.
Often, our groundwater inflow estimates are used to guide contractors in pump selection. The long term steady-state estimates from numerical might be OK.
However, such estimates probably represent significant underestimate of the initial heading inflow rate coming from narrow zones of higher permeability that contractors may have to deal with.
Now, the actual question.  How do you deal with the initial heading inflow rate estimates? Is this the kind of estimate we should try to derive from numerical modelling? Do the the progressive excavation schedule (and geometry) of the excavations and discrete nature of fractures prevent us to provide realistic and timely estimates of these transient groundwater infiltration?
Are Heuer-like empirical equations the best approach for flush flow estimates?
Any thoughts greatly welcome.
Best regards,
Thomas

Hello Feflowers,

I'm at my first heat transport model and I'm wondering what feflow does with the thermal properties when in unsaturated mode...

1- Are the heat conductivity and capacity varied with saturation?
2- When the materials are unsaturated, are these properties modified to take into account the solid-air properties?

I took a quick look at the basic equations in feflow's reference manual, thermal section, but even with it, I'm not entirely sure about it. Probably it's because I'm too good at reading math equations!

What do you think? Any thoughts is welcomed.

Thanks,

Thomas

OK!

pour le français... c'est seulement ton adresse email qui t'a trahi

ciao!

T

Thanks for your answer, Michael.

I was wondering if setting the top slice as phreatic in the unconfined mode was something you sometimes consider?

I think that if you simply run the model confined, the saturated thickness of an aquifer becomes equal to its  total thickness, thus exagerating the transmissivity.

What do you think

Merci bien pour ton temps! ;)

Thomas

Hello all,

I try to run a model of an aquifer system located in a valley surrounded by two hills. This system has two different aquifers. These two aquifers are separated by a confining layer (see a cross section of the problem in the attached file):

1- The upper aquifer is unconfined and found only in the centre part of the valley;
2- The lower aquifer is semi-confined and is found both (a) in the centre of the valley [confined] and (b) on the sides of the neighbouring hills [unconfined]. Looking at the attached file, you will notice that the lower aquifer is made of two different materials.

The confining layer is only found in the centre of the valley.

I try to run this model in steady state for flow only, unconfined. However, the model will only reach convergence if I use the option confined aquifer. According to me, this is not how the system should be modelled, since the upper aquifer and the lower aquifer (on hill sides) have free surfaces...

When I tried to run the model unconfined, I assigned the following slices properties:

Slice 1: Free & Movable
Slices 2-5: Unspecified
Slices 6-11: Fixed (the water level in  the upper aquifer will not get lower than the top of the confining layer )

Any ideas on why the model will not reach convergence when run unconfined? Is there any changes you think I should do?

Thanks

Thomas

I could, but you wouldn't understand!

Hahahhahaha! Just kidding!

The numerical implementation of flow and transport equations is not something I'm familiar with. All I can do is refer you to help (isn't it a fantastic answer?)

I've tried this as I was desperate to see convergence of a mass transport problem in a sub regional scale model...

Take care

Thomas

Hi Michael,

have you tried to modify the type of upwinding (in temporal and control data)?

This is a switch I once pulled when I was facing a similar problem...

Also, there may be something in the Iterative solver settings menu, but I've never dared changing anything in this menu.

Hopefully, I'm not pointing wrong directions...

Good luck: transport convergence for big models can be painful...

Thomas

Thanks for all the information, Chris!

You are contributing a lot to the forum and it is really appreciated.

your IFM work sounds very interesting as all these extra export possibility probably give you a real sharp overview of your input data...

I'll check the forum for launch dates!

Regards,

Thomas

Hi,

I just read the paper ''IFM tool development to streamline data management for large-scale models'' from Chris Gabriel at aquaresource and noticed an IFM module to export particle tracks from FEFLOW to TECPLOT exists.

Will this module eventually be available on wasy website ?

http://www.wasy.de/english/products/feflow/referenzen/module/index.html

If not, is there someone I can contact?

Thanks,

Thomas