Carlos Andres Rivera Villarreyes Global Product Specialist - FEFLOW

Hi Karanka,

I would like to re-open this forum post. [u][i][b]Correction[/b][/i][/u]: Since FEFLOW 6.2 (p8), you have access to the full budget (rate or period). In FePEST we have shortly implemented a new feature, where you can provide a time series (*.pow file) to be used directly for the model calibration.

Regards,
Carlos

Hi Sam,
After the steady-state simulation finishes, simply click on the save (or save as) button. The saved model will contain the steady-state heads.
Cheers,
Carlos

Dear Karanka,
Unfortunately, such as plug-in does not exist. If you have some experience with programming in C++, the plug-in would not be a big deal...
Regards,
Carlos

Hi Karanka,

First in FEFLOW, you would need to activate the budget history charting mode in a selection with the spring nodes. Then FePEST can recognize the budget activation and provide the option of creating an "Observation Definition" based on a rate-budget value. At the moment FePEST only supports the budget at the end of the model run or the difference (final - initial). As a first estimate, you may use this option.
You can implement a complete budget calibration via IFM programming. If you have a plug-in, which is able to retrieve the budget fluxes at specific time steps and write them down in a file named ifm.fpo (two-columns format: Obs. Name, Value), then FePEST can read this information and use it for the model calibration. In FePEST, you would need to setup a so-called [color=blue][i][b]IFM-Implemented Observation Definition[/b][/i][/color] with the same number of observations and names.

Regards,
Carlos

Dear Usman,

The Null Space Monte Carlo approach has several variants (conceptually), which may be complicated to explain full details here. For example you could make the analysis with an uncalibrated model (i.e. pre-calibration approach) or after the calibration is done (post-calibration approach). If you are interested in more background, you can get some insight on the philosophy from the now available PEST Book (http://www.pesthomepage.org/PEST-The_Book.php).
You can take PEST out of its box with some help of FePEST. In the next release FEFLOW 7.0, the methods are fully incorporated and straightforward.
For Instance, you could calibrate your model constrained by a Tikhonov regularization and quite-probably using any other device (e.g. such as SVD-Assist). On the basis of the calibrated model, generate parameters as explained below (or other post) using RANDPAR & PNULPAR and finally evaluate the predictive uncertainty from the results of all the realizations.

Regards,
Carlos

Dear Anne,
If you would like to apply an expression for the outflow flux, you can only do it by means of a material property named "Sink/Source" (or Inflow/Outflow on top/bottom for 3D models). If the model is transient for flow, you can simply make a right-click on the parameter name and activate the expression editor. In such a manner, the fluid-flux BC is free for other purposes such as recharge.
Regards,
Carlos

Dear Rapheul,

All the process variable charts (hydraulic-head, concentration and temperature) and budget charts (rate and period) contains always all the time steps used for the model run. If you want to extract information from specific time steps, you can use the standard export based on nodal selections for specific time and/or all times in the DAC file.

Regards,
Carlos

Dear Ali,

There are two possible explanations:
1) The value of PD1 is not so large compared to PD0. Therefore, PEST cannot maximize/minimize the observation. You need to extend your definition of a "calibrated" model in the parameter space.
2) The hydraulic heads are not so sensitive to the calibrated parameters (i.e. the parameters are indeed changing, but the observations do not).

You may try to go further in your analysis and carry out a Monte Carlo analysis with FePEST. You need a couple of manipulations in the command line to get started in FePEST (see the post [color=blue][i][b]"Null space Monte Carlo with FePest?"[/b][/i][/color])

Regards,
Carlos

Dear Ali,

A run under the PEST predictive mode, it means that PEST would start modifying the parameters in other to minimize/maximize certain observation, but keeping the model "calibrated" at the same time.

PD0 is the target objective function. This is the value what you would expect for a calibration model. Normally, you can take this value from a previous PEST run (i.e. standard estimation mode).
PD1 is the acceptable objective function. Since you want to keep the model "calibrated", then you would need to say what "calibrated" status means. This is simply few percentages above PD0 (e.g. 1-2%).
PD2 tells PEST when to change to the next iteration after having try several Marquardt Lambdas.

You can find all the details in the PEST Manual (section 6-14, page 192).

Regards,
Carlos

Hi Thomas,

It is not correct that you set a head BC equal to the topographic level, this would reflect the behavior of a seepage boundary. For an artesian well, the head BC should get a value, which depends on the high pressure located down in the aquifer. I would recommend you the following options:
Head BC -> Pressurized value
Minimum flow-rate constraint = Maximum flow expected through the artesian well in m3/d
Maximum flow-rate constraint = 0 m3/d (avoid possible water inflow).

Depending on the local settings, you may use a discrete feature element (DFE), which can enhance the vertical flow. Thus, the outflow would be mainly dominated by the deeper aquifer and not the shallow locations. Phreatic and piezometric surfaces may be complicated, so the most-correct evaluation can be only reached by using the Richards' approach in FEFLOW.

Regards,
Carlos