Carlos Andres Rivera Villarreyes Business Owner - FEFLOW

Dear Ali,

There is even an easier way. You could use the "Sensitivity" option implemented in the FePEST interface. Such as option is useful to create sensitivity maps based on the Jacobian matrix estimated by PEST. We run the PEST utility named JROW2VEC (see PEST Manual for all the details).

Regards,
Carlos

Dear Usman,

I think the important point to mention is if you want to try these fluxes as parameters or as observations.
If you want to threat them as parameters, i.e. calibrate the boundary fluxes, this is only possible via IFM programming (see previous posts).
If you want to threat the values as observations, this is already implemented in the FePEST interface (after FEFLOW 6.2. patch 5). In the FEM you would need to define the budget groups by activating "Budget Charting Mode" in a nodal selection. Subsequently in FePEST, you can declare these groups as observation definitions.

Regards,
Carlos

Dear Sven,

Every time you modify the problem settings within the interface, FePEST will "realize" these changes and therefore it will ask to re-create the PEST files. Alternatively, you can easily open the PEST Control File from FePEST and modify the single parameter, which controls the termination criteria (NOPTMAX).

By the way, if you stop the PEST run without this has terminated by its own, FePEST will provide the last parameter estimates found by PEST also.

Regards,
Carlos

Dear Ali,

FePEST provides not limitation in respect to the number of parameters to calibrate. If you need to include additional parameter (also with different type), you can simply add a new parameter definition (See User Manual FEFLOW 6.2).

There are a plenty of methods for the sensitivity analysis from local sensitivity, where you modify manually the parameters and evaluate the outputs, until complex global sensitivity methods with random realization of parameters. For this second option, please refer to post [color=blue][i]"Null space Monte Carlo with FePest?"[/i][/color] in this forum. Before entering to the sensitivity analysis, you can take advantage of all the FePEST outputs such as correlation matrix, covariance matrix and eigenvalues/eigenvectors in order to have a first idea about the parameter influence on the FEFLOW problem.

Best regards,
Carlos

[list]Hi,

Based on the number of singular values for a specific problem, PEST and its utilities are able to distinguish between solution parameters and null-space parameters. We use RANDPAR to create random realizations of parameter distributions based on some prior knowledge (i.e. PEST uncertainty file). However, it may be the case that RANDPAR-generated parameters are far away from a calibrated status. That is the reason to use PNULPAR utility, which gets close to a status of “quasi-calibrated” parameters. Since they are not “fully” calibrated yet, we need to optimize each realization. That means if you have for example 500 parameter distributions, after optimizing each set you will obtain 500 calibrated models.
If the total number of parameters is significant per each realization set (i.e.  pilot points).  You can take advantage of the SVD-Assist methodology in PEST. For this task, you need to run for each parameter realization the utility SVDAPREP, which prepares automatically all the files needed before SVD-Assist. Then launch a PEST run with SVD-Assist for each realization.

The second workflow is easier. Let’s say you believe that all parameter realizations are close enough to a “calibrated” stage, and then you may only want to take a single model run for each realization.  This task can be easily carried out by using the new version of PEST and BeoPEST (already available in PEST homepage) and the FePEST interface. The new PEST version contains a /f-switch to launch multiple parameter files (*.PAR) in parallel model. The workflow is the following:

[list]
[li]In FePEST version 6.2, you need to make sure that the new PEST/BeoPEST executables are defined in the interface (Tools -> Option menu), before creating any PEST input file.  [/li]
[li]Open the [color=red][b]run_pest.bat[/b][/color] created by FePEST and edit the end of the following line:
[i] "C:\Program Files\beopest\beopest64.exe" "MonteCarlo.pst" /H :4052 [b][color=red]/f < "pest.in"[/color][/b][/i][/li]
[li]Create the “pest.in” file as follows: root-name of *.PAR files, initial/final number of parameter realizations and output file.
[color=blue][i]Filename
1
500
500
ResultTable.rrf[/i][/color]
[/li]
[li]Go back to the FePEST interface and run PEST without creating again the files.[/li]
[/list]


[/list]

Hi,

The use of a non-Fickian dispersion has been observed relevant for systems with high-concentration differences, for example brine concentrations in deep aquifers or waste disposal in salt formations. This option can be activated directly in the Problem Settings - Transport Settings. Subsequently a parameter "Nonlinear dispersion" is available in the Data Panel in FEFLOW 6.2.

This high-concentration dispersion coefficient varies inversely to the flow velocity. In the FEFLOW Book you can find an analytical expression (Schotting et al. 1999) to calculate this parameter for a range of flow velocity from 10[sup]-5[/sup] and 10[sup]-3[/sup] m/s.

Further information can be found in sections 11.10.1, 11.10.3 and 11.11.6 in the FEFLOW Book.

Best regards,
Carlos

Thank you for the information. We will fix this soon.

Hi Morgan,

Since already a year ago, DHI-WASY has moved its official FEFLOW support address to mikebydhi.de@dhigroup.com. Please try using this email address. If the problem persists, let us know.

Best regards,
Carlos

Dear Dan,

I would not say that there is not water... Although the first five layers are above the phreatic level, you have imposed a residual water in the Problem Settings dialog. Particle tracking is calculated based on Darcy velocities, therefore only if the lateral velocity is negligible the flow as well.
It seems to me (without knowing layer thickness) that you may have a considerable unsaturated zone. You may try the Richards approach for a better approximation of the fluxes in the vadose zone.

Best regards,
Carlos

Dear Sven,

Did you check if the parameter definitions are set as either [color=red][b]none [/b][/color] or [color=red][b]log[/b][/color] (in Default section)? The definition "none" refers that parameter will be adjusted by using its default units (not transformation at all). If a parameter group is set as [color=red][b]"fixed"[/b][/color], this will not be adjusted during the optimization.

There are parameters (e.g. conductivity, transmissivity, etc.) which are easily adjusted by using a log-transformation. [color=blue][i]"Often a proper choice of whether and what parameters should be logarithmically transformed has a pronounced effect on optimisation efficiency; the transformation of some parameters may turn a highly nonlinear problem into a reasonably linear one"[/i] [/color](PEST Manual, 1-8). If we are talking about a coupled process (flow-heat), a high degree of non-linearity is inherent in the problem.

In general, the "standard" (or default) settings need to be reviewed by the modeller. Several of these settings have been taken from the PEST manual, however there may be cases where they are not applicable for all the models.

Best regards,
Carlos