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iMOD User Manual version 5.2 (html)


7.15Interactive Pathline Simulator

(Extension of this functionality is in progress; we expect it will be completed and part of a Deltares-release of the iMOD-executables in February 2016.)

WHY?
Interactive Particle tracking analyses can be essential in understanding how a geohydrological system works. For reasons of system analyses this tool might be having a great additional value. The main purpose of this tool is to gain insight in geohydrological processes by using animated groundwater flows and the ability to interactively change your point of view in a 3D-environment.

WHAT?
iMOD is equipped with iMODPATH that is a modified version of MODPATH version 3 (Pollock, 1994). iMODPATH is a particle tracking code that is used in conjunction with iMODFLOW. After running a iMODFLOW simulation, the user can use the runfile of iMODPATH (see section section 8.7.6) to enter the 3-D tool of iMOD (see section section 7.3). In this 3-D environment, the user is able to interactively analyze the flow path of groundwater particles, e.g. pause the flow at arbitrary moments. Particles can be tracked either forward in time or backward in time.

Note: The IPS runs only for a Steady State flow situation. In case a transient iMODPATH run file is uploaded, only the first stress period is read and used for particle tracking.

HOW?
Select the option Toolbox from the main menu, click on the submenu option Interactive Pathline Simulator and then on Start IPS… to select an appropriated runfile for iMODPATH. The 3-D tool will start and all the necessary files (top, bottom and fluxes) will be allocated for the current zoom extent. It is easily to start the tool for limited areas of interest, especially to be more efficient. On default iMOD starts the IPS with default display settings (checked in IPS-submenu), this means that all the files available in the runfile are loaded into the 3D-tool. Another option is to choose User Defined Display and iMOD only loads the files selected in the iMOD manager.

IPS-submenu:

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3D Plot Settings window, Pathlines Folder tab:

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Start Point
Definition

With the following options the starting point of the particles can be defined.

Area:

Select this option to define a rectangular area with starting points somewhere in the modeled area.


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Select
Click on this button to drag a rectangle (NOT AVAILABLE IN CURRENT VERSION!).


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Attributes
Click on this button to open the
Location Settings window:
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Enter the minimum and maximum x, y and z-coordinates to define the extent of the box in which the starting points needs to be placed.

XY interval

Enter a value for the amount of staring points in x- and y-direction.

Z

Enter a value for the amount of starting points in the z-direction.

Configure
Particles…

Click on this option to open the Particle Settings window:
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Act.

Check this option to activate a particle group.

Colour

Click on this field to change the colour of the particles and starting points.

No. Particles

Total amount of particles in a group.

BW/FW

Click on this field to change the tracking option in "Forward" or "Backward".

SP-Size

Click on this field to change the size of the starting point.

P-Size

Click on this field to change the size of the particle.


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Open PTF
Opens an PTF(Particle Tracking File)-file containing the particle settings per group.


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Save As
Saves the particle group settings in a IPF-file, if points needs to be analyzed in iMOD separately from the IPS-tool, or in a PTF-file for later use in IPS.

IDF:

Select this option to define the starting points based on the in a loaded IDF-file available points. Make use of the dropdown menu to select the preferred IDF-file.


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Attributes
Click on this button to open the window IDF Settings:
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Flux Depending

Select from the dropdown menu the preferred vertical direction of the flux in a particle related cell: Up (only positive fluxes are drawn), Down (only negative fluxes are drawn) or both (all fluxes are taken into account).

Layer

iMOD uses the fluxes from the layer defined with this option, e.g. if Layer=1, iMOD uses the fluxes from model layer 1.

XY Sampling

Give the horizontal distance in meters between the starting points.

Vertical Offset

Give the vertical distance in meters between the top of the layer and the particle start position.

Randomize

Check this option to randomly place the starting points with the given settings.

Sink:

Select this option to locate the starting points on the location of the in the model area available sinks. Check Strong to apply the given condition, defined with the dropdown menu and the value box, only to strong sinks. The background theory about strong and weak sinks can be found in section 7.14 under Weak Sinks tab.


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Attributes
Click on this button to open the window Sink Settings:
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Shape:

Choose the shape of the points on the sink locations; Square or Circle.

Radius (meter)

Enter the size of the radius in meters of the sinks related points.

Sample on
circle

Enter a value for the horizontal influence area around the sink (in meters) to be shown in the simulation.

Vertical
sampling

Enter the amount of starting points per layer in the vertical direction at the sink location, e.g. if 5 layers are selected and a vertical sampling amount of 10 is chosen, there will be in total 5x10=50 starting points in the vertical direction.

Extraction
rate:

Define the range of the sink extraction rate. Only sinks with discharges within the given range are labeled as sinks.

Randomize
positions

Check this option to randomly place the starting points with the given settings.

Layers

Select the layers to be taken into account in the PTS at the well locations (e.g. selecting 5 layers results into 5 groups with each the total amount of defined starting points).

Treat subsequent
Layers as One

Check this option to evaluate all selected layers as one layer (be aware: only successive layers are consolidated to one layer), e.g. 5 selected layers with 10 vertical samples results in 50 starting points, with this option checked on there is only 1 group with 5 layers and 10 starting points in total.

Create
Separate Groups

Check this option if it is preferred to treat each selected layer as an separate subgroup within 1 group, e.g. 1 group is made with the 5 selected layers, each containing 10 starting points (50 starting points in total).

Layer:

Select this option to locate the particles at one of the displayed model boundaries. W=West boundary, N=North boundary, E=East boundary, S=South boundary and A=all boundaries.


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Attributes
Click on this button to open the window Layer Settings:
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In this window it is possible to i.e. select the layers to place the starting points in.

Layers

Select the layers to be taken into account in the PTS at the border location(s).

Treat Subsequent
Layers as One

Check this option to evaluate all selected layers as one layer (be aware: only successive layers are consolidated to one layer).

Z

Enter the amount of starting points per layer in the vertical direction.

XY Sampling

Give the horizontal distance in meters between the starting points.

Randomize

Check this option to randomly place the starting points with the given settings.

Create
Separate Groups

Check this option if it is preferred to treat each selected layer as an separate subgroup within 1 group, e.g. 1 group is made with the 5 selected layers, each containing 10 starting points (50 starting points in total).

File:

Select this option to choose an IDF- or IPF-file for the start point definition.


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Open
Use this button to search for and open the preferred file.


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Attributes
Click on this button to open the window IDF Settings which is similar to the IDF-option settings window.


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New
Click on this button to reset the Particle settings, the Part. value boxes are set on 0.


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Add
Click on this button to add a new PSP (Particle Start Point) definition group to the simulation. Every time this button is used a new group is added to the particle simulation and the value in the first Part. value box is increased with 1.


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Show Selection
Click on this button to analyze the location of the defined particles in advance of or during the particle simulation.


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Color
Click on this button the change the color of the just defined point-group.

Part.

The first value box counts the amount of PSP definition groups specified by the user. Every time the ( pictures/h72-end/image1158.png)-button is used, this value is increased with 1 (total value = amount of defined particle groups). In this case 4 start point definitions are specified. The second value box is the sum of all the defined starting points (in this case 5520). By clicking on Configure Particles…the total amount of particles per start point definition can be distinguished.

Particle Tracking

With the below mentioned options it is possible to set the graphic settings of the particle tracking. A change in some of the options is directly visible on screen.

Appearance:

Choose the representation of the simulated path line points; Lines, Points or Voxels (Not Available yet).

Weak Sinks:

Make a choice between "Use spec. fraction", "Particles stop…" and "Particles pass…". Selecting "Use spec. fraction" allows the user to enter a fraction number in between 0 and 1 (See page 368 at Particles are stopped when they enter… for a more extended description). The other two menu items use a fixed factor value in their selection (see page 368 for an extended explanation about these other two Weak Sinks options).

Maximum
Travel time
(year):

Give the maximum time a particle can travel through the model area during the simulation before the particle disappears from the screen or restarts from its starting point, e.g. a value of 1000 years gives the user the opportunity to follow a particle for 1000 years of simulation time.

Intermediate
Travel steps
(year):

Give the time step size in between two shown particles. Examples: 1. an intermediate travel step of 0.10 year and a maximum travel time of 10 years results into 100 time steps, 2. An intermediate travel step of 1 year, on the other hand, and the same maximum travel time (10 years) results in 10 time steps. The actual time of the simulation is longer in the first example compared to the second example, because the actual simulation time is based on the amount of time steps (more=longer).

Tail Length

Enter a value to define the length of the particle "shadow". The shadow shows a part (the length of the tail) of the particles pathline, in real life comparable to the contrails of aircrafts in the sky.

Repeat
when trapped

Check this option to restart a particle at its starting point after the particle disappeared, e.g. it was trapped in a sink or it flews outside the model domain (only available when Repeat Freq. is not checked).

Repeat Freq.

Check this option to restart a particle after the entered time step value, e.g. at a frequency of 1.00 iMOD starts a new particle simulation every year of simulation time (only available when Repeat
when trapped
is not checked).

Filter part.
whenever captured by:

Check this option to be able to apply a particle filter to the whole simulated particle cloud. In this refinement there are the following options:
1. Inactive cell: restart only the particles in the simulation that are captured by an inactive cell.
2. Zero velocity: restart only particles that have no velocity at the moment they are trapped.
3. Strong sink: restart only the particles that are captured by strong sink(s).
4. Weak sink disregard flux: restart only the particles that are trapped by weak sinks with a negligible flux compared to the total inflow.
5. Weak sink flux gt frac: restart only the particles that are stopped by weak sinks with a flux larger than the fraction of the total inflow.
6. Boundary grid reached: restart only the particles that reached the boundary of the presented model grid.
7. T greather than max T: Restart all particles when the current simulation time is greater than the maximum Travel time.

Start

Click on this button to start the simulation.

Stop

Click on this button to stop the simulation.

Backward

Select this option to track the particles backward.

Forward

Select this option to track the particles forward.

Current Time
of Simulation
(year):

Counter for displaying the current time of simulation. It counts from 0 until the set Maximum Traveltime (years) with a time step given by textitIntermediate Travelsteps (year). The counter starts over again, when the maximum travel time is reached and a repeat-option is selected.

Active
Particles:

Counters for the total amount of particles at the beginning of the simulation (left value box) and the amount of active particles during the simulation (right value box).