Denim Umeshkumar Anajwala

Hi All!
i want to import to my model a time-series of recharge.
what method should i use?

i already have rain-stations in which the time-series are known.
now i need to change the file format to one which FEFLOW can import.

maybe there are another suggestions? what abou T-List? how should i use it?

Elad

hello!

I would like to know if there are rule of thumbs for cells and layers dimensions? More precisely:

1- a horizontal to vertical dimension ratio?
2- a minimum thickness for a layer?

any references?

thanks

Boris -- is it one to two meters per layer, or one to two meters total domain height?

In the first case, the vertical resolution would be almost certainly too coarse if you use any of the nonlinear pressure-saturation functions such as van Genuchten.

In the second case, the resolution might be sufficient (~10 to 20 cm per layer) but we should still take a look at the parameters, especially the 'A' parameter if it's the van Genuchten model.

Volker

Hello Boris,

A potential source of error for unsaturated models is insufficient vertical resolution. What are the approximate dimensions of your model domain; in particular, how many elements are available to resolve its vertical extent?

Volker

Peter Schatzl: YOU solved my problem!
Many many thanks!
Thomas

Hi there,

I'm modelling  Steady Mass Transport (in 3D) using 1st kind Mass Transport Boundaries as a source.

To me, the expected result should be a plume moving downgradient from the source and ending at the lower head boundary, which is about 2 Km away from the source. This is supported by field observation on the plume shape. Actually, I've already modelled the same setting using FRAC3D and obtained such results.
However, the plume modelled using FEFLOW doesn't reach the boundary of the model: it simply vanishes somewhere halfway to reach 0 mg/L. Could someone explain this to me?

Here are some of the parameters I used in this model that might explain this behaviour:

Saturated media
Flow and mass transport (both are steady)
Recharge (In(+)/Out(-) flow on top): 8.2 x10-4 m/d (300 mm/yr)
Unconfined
Longitudinal dispersivity: 5m
Transverse dispersivity: 0.5m
Linear (std) dispersion
Diffusion: 1x10-9 m2/s
No decay or  Sorption

Solver settings: Preconditionned restarted ORTHOMIN... (since the defaults would not work)

Cheers!
Thomas

Hi all!
i'm running a model with a single phreatic/confined layer.
-when i'm using "unconstained" for dring cells, my water budget is OK.
-when i'm using "constrained" to prevent cell drying and a "residual water depth"
  the outflow is much higher that inflow.

is that mean that FEFLOW solve the residual watertable issue by entering additional water to the dring cells?

if it so, i understand that i need to 1) not use the constarin option. 2) lower the conductivity on the area that is subject to drying.

is there another way to overcome this problem?
 

hi!
i've found out that once the screen is in zoom on part of the model than only the point/polygons which show on the screen are exported.
it may be a bug in the FEFLOW code  ::), but it can be useful for you.
so, you should focus on the area (rectangle) you want to study and then do the export procedure.

Elad Dafny

Hi mate,

the answer hides in your question.
whenever you wish to "fix" your layers you should use "fixed" option.
as i understand it, the moveable layers option was created for the upper layers of phreatic aquifers, in which groundwater table can shift up and down.  so, this option is actualy 1) raise your resolution and 2) allow you to change groundwater table without driyng the uppermost cells.
i don't think that there is a "rule" for your question, rather, you should (and did)used your common sense.

Elad

I've been having the same problem on long runs. FEFLOW stops and exits without warning or error messages. It is sporadic, and impossible to reproduce. It has happend to me overnight, but also during the day.

It does not seem to be a power spike affecting my computer as other applications I have open are still running fine. Furthermore, previous experience demonstrates that power spikes result in the PC shutting down, not automatically restarting and reopening applications running previously.

We though it might be MS or Norton automatic updates. Investigation proved otherwise.

It is possibly a power spike on the server (were the license resides) but probably not for the same reasons above. My IT guy does not report anything unusual with the server coinciding with the times it shuts down.

My guess is that it is FEFLOW, and not a power interruption issue. It is an inconvience, but not a disaster.