pictures/imod_logo.png

iMOD User Manual version 5.2 (html)


7.9Start Model Simulation

WHY?
A runfile is required for a groundwater flow model that is configured with the iMOD concept. Such a runfile (see chapter 10) consists of a header with general information about the location, horizontal resolution, number of modellayers and solver settings. This type of information can be easily modified in the Start Model Simulation Tool described in this section. A runfile can be constructed using the Project Manager, see section 5.5. Alternatively, a simulation can be initiated using the Project Manager and/or using the iMOD Batch Function RUNFILE, see section 8.7.5.

WHAT?
It takes two requirements to start a model simulation within iMOD:

HOW?
Select the option Toolbox from the main menu and then choose the option Start Model Simulation to display the Start Model Simulation window.

Start Model Simulation window, Main Configuration tab:

pictures/h5/image763.png

Runfiles (*.run)

This list displays the existing runfiles (*.run) in the folder {user}\runfiles (for more detailed information on runfiles see chapter Runfile). Whenever a runfile is selected, iMOD will try to read the header information and if no errors are found, the extent of the model (as described by the BNDFILE in the runfile) will be displayed on the graphical display (hatched area).


Example of the graphical display:

pictures/h5/image764.png


pictures/h5/image765.png

CheckRun
Click this button to check the existence of all files in the selected runfile. iMOD will check files with the extensions *.IDF, *.IPF, *.ISG and *.GEN as these are valid to be used in a runfile. A list of all missing files are recorded in a file: {user}\tmp\runfile.log.

Example of a runfile.log:

pictures/h5/image766.png


pictures/h5/image767.png

Info
Click this button to display the content of the selected runfile (*.RUN) in a texteditor.


pictures/h5/image768.png

RunfileCopy
Click this button to make a complete copy of the content of the selected runfile for the current window. All IDF and IPF files that can be found in the runfile will be clipped to this window.


pictures/h5/image769.png

Project Manager
Click this button to display the Project Manager (section 5.5) and read in the selected runfile. This might be handy as different runfiles can be generated from the Project Manager as well as steering a runfile from the iMOD Batch Function RUNFILE (section 8.7.5) is more efficient for simulations that need to be carried repeatedly.


pictures/h5/image770.png

ZoomFull
Click this icon to zoom to the entire extent of the model.

Help …

Click this button to start the HELP functionality.

Close

Click this button to close the Start Model Simulation window.

Start Model Simulation window, Model Dimensions tab:

pictures/h5/image772.png

Number of Modellayers

Select the number of modellayers to be used in the current model simulation. Whenever the Number of Modellayers is less than the MXNLAY variable in the run-file, iMOD will display a message at the right of the dropdown menu, indicating that the boundary condition of the lowest modellayer will be a Constant Head boundary condition.

Define Spatial Dimensions Interactively

Select this option to determine the dimension and size of the rastercells (computational nodes) interactively.

Draw Simulation Area of Interest

Click this button to start drawing a rectangle on the graphical display to indicate the location of the simulation area (hatched area). Use your left-mouse button to position the first points of the rectangle, use the left/right-mouse button to identify the opposite border. Whenever you move the mouse cursor inside the hatched area, a cross-arrow appears indicating that the entire hatched area can be moved while clicking the left-mouse button. Similar the borders can be moved whenever the horizontal/vertical arrows appear.

Example of a model extent after drawn interactively on the graphical display:

pictures/h5/image778.png

XULC,XURC, DeltaX

Enter the X-coordinate for the lower-left-corner (XULC) and the upper-right-corner (XURC). The difference between them will be computed automatically (DeltaX). All variables need to be entered in meters, moreover, they will be filled in automatically whenever the simulation area is adjusted interactively on the graphical display.

YULC,YURC, DeltaY

Enter the Y-coordinate for the lower-left-corner (YULC) and the upper-right-corner (YURC). The difference between them will be computed automatically (DeltaY). All variables need to be entered in meters, moreover, they will be filled in automatically whenever the simulation area is adjusted interactively on the graphical display.

Simulate model
with cellsizes
equal to

Select one of the cellsize from the dropdown menu or enter a value in the input field next to it.

Include a Buffer-
zone of:

Select one of the buffersizes from the dropdown menu or enter a value in the input field next to it. The Buffer-zone is an extra “ring” of modelcells around the chosen simulation area and indicated by a green rectangle.

Increase Cellsize
in buffer upto:

Select this option to increase the cellsizes in the Buffer-zone upto a cellsize that can be selected from the dropdown menu or entered in the input field next to it.

Snap Coordinates to Entered Cellsize

Select this option to snap the coordinates of the model domain to the entered cellsizes. In this manner, the coordinates of the model will have ”nice-and-round” coordinates.

Use Spatial
Dimensions
Defined in IDF:

Select this option whenever an (ir)regular network needs to be used that is described in the header information of an IDF that can be entered in the corresponding input field.


pictures/h5/image779.png

Open IDF
Select this button to select an IDF-file from the system.

pictures/h5/image780.png

Figure 7.1: Start Model Simulation window, Solver Settings tab

Number of outer
iterations:

Enter the maximum number of outer iterations.

Number of inner
iterations:

Enter the maximum number of inner iterations.

Head closure
criterion:

Enter the maximum head residual in meters.

Budget closure
criterion:

Enter the maximum budget residual in cubic meters.

Use
Dampingfactor

Check this option to include adaptive damping. The relaxation factor (RELAX) will be adjusted according to Cooley’s method with Huyakorn’s modification. This will increase convergence for a nonlinear model.

Relax parameter:

Enter the relaxation parameter (0.0 \(<\) relax \(<\) 1.0)

Acceptable
Overall
Waterbalance
Error

Enter the overall acceptable waterbalance error in percentage of the waterbalance error (Q\({}_{in}\)-Q\({}_{out}\)) divided by the mean of the absolute total of both: 0.5*(Q\({}_{in}\)+Q\({}_{out}\)). Whenever the simulation can not find a solution within the number of outer * inner iterations, it can still continue whenever it meets the Acceptable Overall Waterbalance Error.

Acceptable
Number of Inner
Convergences

Enter the number of sequential inner convergences that forces the solver to stop further iteration. The simulation will continue whenever the result passes the Acceptable Overall Waterbalance Error too.

Preconditioning:

Choose the preferred pre-conditioning method (only possible when using the PCG-solver):
1. Modified Incomplete Cholesky (for use on scalar computers),
2. Polynomial matrix conditioning method (for use on vector computers or to conserve computer memory).
If the Preconditioning Method is set to Cholesky, the Relaxation parameter can be set. Although the default is 1, in some cases a value of 0.97-0.99 may reduce the number of iterations required for convergence.

Minimal
Transmissivity:

Enter a value for the minimal transmissivity that may occur in the model. In case a grid value is found below this threshold this will be corrected before the model simulation is started.

Minimal Vertical
Resistance:

Enter a value for the minimal vertical resisitance that may occur in the model. In case a grid value is found below this threshold this will be corrected before the model simulation is started

Preferred method
of subdomain
partition:

Choose the preferred subdomain partition option. There are two methods supported:
1. Uniform subdomain partitioning (default) for uniform partitioning in lateral x and y-direction,
2. Recursive Coordinate Bisection (RCB) subdomain partitioning that computes the subdomain dimensions according to be specified pointer IDF grid (selecting a pointer IDF-file is required with this option).
By selecting None the PKS package will not be used during the simulation. Note: Each subdomain always includes all model layers.

Load pointer
IDF-file:

In case hte RCB option is chosen, the filename of the needed pointer IDF grid needs to be filled in here.


pictures/h5/image801.png

Open
Click this button to find and select an IDF-file with the needed PKS pointer information.

Merging IDF
output files
of subdomain

Check this option if merging of parallel subdomain IDF output files is needed (see for more information section 10.6). Note: Enabling this option could slow down overall parallel computations.

Note: Consult scientific literature regarding the Solver Settings as described above in order to avoid any unwise input.

Start Model Simulation window, Output Variables tab:

pictures/h5/image782.png

Result Variable

This list will display the available output variables that are within the selected runfile from the Main Configuration tab. Select one of the following:

File (*.idf)

Variable

Description

SIMGRO

Flux in/out Simgro elements

BDGBND

BOUNDARY

Flux in/out constant head boundaries

HEAD

GROUNDWATERHEAD

Groundwater head

BDGFFF/BDGFRF

FLUX FRONT/RIGHT FACE

Flux in/out front/right cell faces

BDGFLF

FLUX LOWER FACE

Flux in/out bottom cell face

BDGSTO

STORAGE

Flux in/out storage

PURGED WATER TABLE

Absent

ANISOTROPY

Absent

HORIZ.FLOW BARRIER

Absent

TOP

Absent

BOT

Absent

CONCENTRATION

Absent

HORIZ.K VALUE

Absent

VERT.K VALUE

Absent

BDGWEL

WELLS

Flux in/out well systems

BDGDRN

DRAINAGE

Flux out drainage systems

BDGRIV

RIVERS

Flux in/out river systems

BDGEVT

EVAPOTRANSPIRATION

Flux out evapotranspiration

BDGGHB

GENERAL HEAD BOUNDARY

Flux in/out general head boundaries

BDGRCH

RECHARGE

Flux in recharge

BDGOLF

OVERLAND FLOW

Flux out overland flow

BDGBND

CONSTANT HEAD

Flux in/out constant head boundaries (identical to BOUNDARY)

BDGISG

SEGMENT RIVERS

Flux in/out river systems

BDGIBS

INTERBED STORAGE

Flux in/out interbeds

Selected
Layers

Select the modellayers for which the current selected variable need to be saved. The number of modellayers to choose from is determined by the Number of Modellayers selected in the Model Dimensions tab.

SaveBudget Terms for each
Boundary System

Select this item to save budget terms for each of the defined sub-systems in the selected runfile. Each subsystem will be added to the filename, e.g. bdgriv_sys1_steady-state_l1.idf.

Saved Result
Variable inclu-
sive the given
Buffer Size

Select this item to save the results within the specified buffer size entered in the Include a Buffer-zone of field on the Model Dimensions tab.

Save Results in Double Precision

Select this option to save all results in double precision accuracy instead of single precision (which is the default). Bear in mind that all files will be doubled in size as well as the option for double precision is selected. Also, result files saved in double precision cannot be read in iMOD version older than v3.4.

Start Model Simulation window, Result Folder tab:

pictures/h5/image783.png

Enter or Select
Output Folder

The selected variables, as specified in the Output Variables tab, will be saved in the folder entered/selected here. Each variable will be saved within a separate folder, e.g. {outputfolder}\BDGRCH\BDGRCH_STEADY-STATE_L1.IDF.

Block iMOD from Using …

Click this option to block iMOD from usage during a simulation. iMOD becomes available whenever the simulation terminates. Unchecking this option allows to use iMOD directly after launching the simulation. There will be no message whenever the simulation is finished, this need to be examined outside iMOD.

Redirect output of Simulation Window in Logfile …

Click this option to redirect all information from the window echo into a separate file called RUN_LOG.TXT. This file will be saved in the simulation folder and contains all echo information of the simulation. Use this file whenever a simulation abort unexpectedly.

Start Model
Simulation …

Click this button to start a model simulation. iMOD will ask you to confirm, before the actual simulation starts.