Tutorial Parameters

In the following exercises we use different methods to assign process varia­bles, boundary conditions, constraints, material properties and discrete fea­tures.

Click  Open and load the file parameters.fem. This model is a 3D tran­sient flow and transient mass-transport model.

 

Selection toolbar.

 

Editor toolbar.

 

Snap-Distance toolbar.

Assignment of Constant Values

In the first exercise we assign constant values manually. We start with the assignment of boundary conditions and constraints for flow and mass trans­port.

Set the 3D view active, go to the  Data panel and activate Boundary Con­ditions (BC) > Fluid flow > Hydraulic-head BC with a double-click. Next, select the nodes to which the boundary condition is to be assigned. We use the node selections displayed in the  Selections panel to set a selection. Double-click on Southern Border to set the selection active. The selected nodes of the southern border now appear as yellow spheres.

Now, enter a value of  32.1 m in the input box of the  Editor toolbar and click  Assign. The selected nodes are now surrounded by blue cir­cles, the symbol for a 1^st kind boundary condition. Clear the selection with a click on and proceed with the northern border.

 

Boundary conditions at southern border.

Double-click on Northern Border in the  Selections panel to set this node selection active. Enter  46 m in the Editor toolbar and click the green check mark to assign the value.

We proceed with the assignment of mass-transport boundary conditions for the two borders. Go to the  Entities panel and click on Domain. In the  Data panel, activate the parameter Mass transport > Mass-concentra­tion BC. In the  Selections panel open the context menu of Southern Border. This time, select the option  Add to Current Selection to select all nodes at both the southern and the northern borders. Type a value of  0 mg/l in the Editor input box and click Assign.

To ensure the possibility of a free outflow of mass at these borders we add a constraint. First, click on Domain in the  Entities panel again. In the  Data panel, open the context menu of Mass-concentration BC and select  Add Parameter > Min. mass-flow constraint. Double-click on  0 g/d in the input box of the  Editor toolbar and assign the value with a click on the green check mark. The constraint will limit the applicability of the 0 mg/l fixed-concentra­tion BC to flow entering the model domain (here treated as positive). At BC nodes with outgoing (here negative) flow, the fixed-concentration BC will be replaced by the constraint. The minimum constraints are displayed as white bars below the boundary-condition symbols in the model. Make sure to clear any selection before proceeding to the next assignment.

 

Adding constraints.

Assignment of Time-Series Data

We assume a mass source that is defined as time-varying mass-flux bound­ary condition in our model. We therefore use a time series to assign time-var­ying boundary condition values.

Open the Time-Series Editor via  Edit > Time Series. The ID list on the top left of the dialog is still empty and shows that the model does not contain any time series yet. To load the time series click on  Import and choose the file massflux.pow.

This file contains one times series with the ID 10 that is now added to the time-series list. Before the time series can be assigned, we need to include a gap in the series in order to turn the boundary condition off during a specific time period. Additionally, we need to define the unit class of the time-series values. The time-series graph currently shows a linear increase of the mass flux between days 60 and 90. In order to deactivate the boundary condition between these two time stages, we include a gap after day 60. To do so, click into the line for day 60 in the time/value list on the right-hand side of the editor and then click on Insert Gap.

 

Time series including a gap.

Both the time/value list and the time-series graph now reflect that the bound­ary condition will be turned off between days 60 and 90.

To change the unit class of the time-series values, right-click on Value, select  Change Unit Class and then click on  Integrated mass rate. The dis­played user unit now switches from cardinal to [g/m²/d].

Click on  Apply and  OK to confirm the changes and to leave the dia­log.

Make sure that the Slice view is the active view and that Slice 1 in the  Entities panel is selected. Double-click on Mass transport > Mass-flux BC in the  Data panel and also on the stored node selection Mass Source to set the selection active. To assign the time-varying mass flux, click on the symbol in the input box of the  Editor toolbar until it switches to  Time Series input mode and the time series for the mass-flux boundary condition is displayed. Complete the assignment with a click on  Assign. The time-varying character of the boundary condition is indicated by a white wave sym­bol on top of the boundary condition in the active view. The time-series ID is also displayed next to the BC symbol.

 

Time-varying mass-flux BCs.

Assignment of Map Data

Interactive Data Input

To complete the boundary conditions we assign a fixed concentration (1st kind Mass BC) to the nodes of the two contamination sites.

Instead of creating a selection prior to the parameter assignment, we perform the assignment using the map geometry as target geometry.

First, click on Slice 1 in the  Entities panel when the Slice view is the active view. Activate the parameter Mass-concentration BC in the  Data panel. Double-click Supermesh > Polygons in the  Maps panel. Enter a concentration of  500 mg/l and switch to the now active tool  Assign Data by Map Polygon located in the map-assignment tools next to the input field of the Snap distance to  1 m in the  Snap-Distance toolbar to limit the selection to the nodes within the con­tamination sites. Click on Clear to deactivate the selection. Move the mouse cursor over the contamination sites until they are highlighted. Assign the concentration with a single click into each of these areas. The boundary conditions now appear as blue circles around the nodes.

 

 Highlighted contamination site (left) and assigned boundary conditions (right).

Automatic Data Input

Parameter Association, Regionalization and Assignment

Having the boundary-condition assignment completed we proceed with the assignment of material properties. To assign values for hydraulic conductivity and recharge we use some of the maps that are included with the model. These contain attribute values which have to be linked to the respective FEFLOW parameters.

Start with assigning hydraulic-conductivity values to the top layer of the model. Go to the con­duc2d with a right-click. Select the entry  Link to Parameter to open the Parameter Association dialog.

The list on the left hand side contains the attribute data which are stored in the map. Click on CONDUCT. To link these data to the FEFLOW parameter now double-click on Material Properties > Fluid flow > Conductivity K_xx in the list on the right hand side. A black line shows the created link. The link properties are edited in the table below.

Leave the Time constant data and set [10-4 m/s] as Source data unit for the conductivity values. Do not change the fields Element/Layer Selection and Default Link Selection.

As the map contains point data, we need to define a regionalization method for data assignment.

From the list of available methods select the Akima method. Set a Linear as Interpolation Type and choose 3 Neighbors and 0 Over-/Under Shooting. Confirm the link settings and leave the dialog with  OK.

To assign the linked conductivity Data, make sure that the  view is the active view and double-click on the entry for the link in the  Maps panel. Conductivity K_xx now becomes the active parameter in the  Data panel, the assignment mode is changed to Maps and the correct map for assign­ment is automatically set in the input field of the  Editor toolbar.

Browse to slice 1 in the Entities panel and click on  Select All. To assign the data click the green check mark in the  Editor toolbar.

Assignment via Quick Import

To demonstrate how all or multiple exported model parameters can conven­iently be re-imported into the same model or an alternative scenario of the same model we export all boundary conditions and then reassign them using the Quick Import option.

To export all flow and mass-transport boundary conditions into one file, right-click on Boundary Conditions (BC) and select  Export Data > All Nodes and save the file as boundary_conditions.shp. Confirm the automatic add­ing of the map to the current model with  Yes. The map boundary_condi­tions.shp now appears under Exported Maps section in the Maps panel.

To illustrate that all boundary conditions are assigned correctly via the  Quick Import, we delete all boundary conditions first. The fastest option to do this is again to right-click on Boundary Conditions (BC) in the  Data panel and to select  Assign Multiple. Make sure that the setting  Apply to entire model domain is active and confirm the deletion with  OK.

Now, go to the  Maps panel, right-click on the map boundary_conditions.shp and select  Quick Import from the context menu. Make sure that all the boundary-condition types that we want to re-import are checked. Choose the option  Select by node number as Node Selection Mode and  Apply to entire model domain as Model Domain. After clicking on  OK all fluid-flow and mass-transport boundary conditions are re-im­ported.

 

Assignment via Quick Import.

Assignment via Expression

The hydraulic conductivity in z-direction is assumed to be smaller by a factor of ten than the conductivity in x-direction. To assign the conductivity values in z-direction, a user-defined expression is applied.

In the  Data panel, double-click on Conductivity K_zz. Right-click on the symbol in the input box of the  Editor toolbar and switch to Expression assignment mode. Open the Expression Editor with a double-click on Cur­rent Expression in the input box of the  Editor toolbar. Delete Current in the working window and open Material Properties > Fluid flow > Conduc­tivity in the list of model parameters on the right-hand side of the dialog. Dou­ble-click on CONDX and then click on the Insert a fraction template symbol. To complete the expression, click into the blue input box and enter  10. Hydraulic conductivity in z-direction is now linked to conductivity in x-direction.

Leave the dialog with Close button and click on   Select All in the Slice view and execute the assignment with a click on  Assign. The completed expression is shown in image below:

 

Expression-based assignment.

Assignment via Copy and Paste

For the conductivity in y-direction the same values as for the x-direction shall be applied. To assign the values, copy the K_xx values to the parameter K_yy.

First, a selection needs to be created from which parameter values will be copied. Again, select all elements of the top layer with  Select All. In the  Data panel, open the context menu of Conductivity K_xx and click on  Copy. Then, right-click on the parameter Conductivity K_yy and select  Paste.

Values cannot only be copied to other parameters but also to the same parameter on a different slice or layer. Make sure to click  Clear before proceeding. Browse to Layer 3 in the  Entities panel and select all elements of this layer with a click on Select All.

Now double-click on Drain-/fillable porosity in the  Data panel and select the option  Copy from the context menu of the parameter. Open the con­text menu once more, click on  Paste to Slice/Layer and select layer 1 as target layer. The values for Drain-/fillable porosity are now copied from layer 3 to layer 1.

Parameter assignment using Copy/Paste.

Assign Multiple Parameters

The material properties for mass transport are assumed to be homogeneous throughout the entire model domain. Except for the parameters Transverse dispersivity the already assigned values are accepted.

To edit these two parameters simultaneously, open the context menu of Material Properties > Mass transport in the  Data panel, with a right-click and select  Assign Multiple. Deactivate all parameters except for the two dispersivities. Double-click into the Value field for Longitudinal dispersivity and enter a value of  70 m. Press the <Tab> key on the keyboard and enter 7 m as Transverse dispersivity value. Make sure that the option  Apply to entire model domain is selected and confirm the assignment with  OK.

Time-Varying Material Property Assignment

Continue with assigning recharge which in FEFLOW is treated as a material property. Go to the  Maps panel and select  Link to Parameter in the context menu of the map year_rec to open the Parameter Association dia­log.

The map contains five different datasets which we will assign as cyclic tran­sient recharge data. To define time-varying recharge values, open the context menu of In/outflow on top/bottom in the list on the right hand side and select the option Assign material Data to time stages. In the Material Data Time Stages dialog, click on  Import... and select the file material_­times.pow to load the time stages for which the input map contains recharge Data. Confirm the import with  OK. The loaded time stages are now listed below In/outflow on top bottom. Click on the entry ULTRAWET_Y, hold the <Shift> key and click on ULTRADRY_Y. To set all links between the map attributes and the corresponding material times at once, double-click on 0 [d] on the right-hand side. Black lines indicate that five links have been defined. Click on one of the links to display the link settings.

As source data unit for the recharge values keep the default unit of [10 ^-4 m/d]. Do not modify the fields Element/Layer Selection and Default Link Selection. As this map is a polygon shape file no regionalization is necessary to import the data. All necessary settings are shown below.

 

Parameter Association dialog for time-varying recharge Data.

Click on  OK to confirm the settings and to leave the dialog. The link between the map data and the FEFLOW parameter is now shown in the  Maps panel in the tree year_rec > Linked attributes.

To assign the linked recharge data, reduce the snap distance to 0 m and follow the same steps as for the assignment of hydraulic conductivity in sec­tion

The legend of In/outflow on top/bottom in the Slice view displays the time stage that the plotted parameter distribution belongs to.

To use the defined recharge values in cyclic mode, open the context menu of In/outflow on top/bottom in the  Data panel and select  Edit Time Dependency > Cyclic.

Assignment via Interactive 1D Interpolation

In the next step a time constant boundary condition is assigned via Interac­tive 1D Linear Interpolation. The boundary condition is assigned along the outer model boundary but the interpolation at locations within the model domain works completely analogously.

Make sure that the Slice view is the active view and navigate to the top slice via the  Entities panel. Activate the boundary condition Hydraulic-head BC with a double click on the parameter in the  Data panel. Once the boundary condition is activated for assignment, the tool  Linear 1D Inter­polation becomes available in the drop-down list of tools located at the far right in the  Editor toolbar. To use the tool, simply click on it.

We will define both the geometry and the values to be used for the interpola­tion interactively. In the input field of the  Editor toolbar, enter a value of 40 m and click on a node along the model boundary in the East while you keep the <Ctrl> assigns the value, time series or expression currently entered in the Editor toolbar at the selected node location while a simple click only adds a vertex along the inter­polation path without a value. The assigned head value of 40 m is automati­cally displayed next to the first vertex.

Place additional vertices along the outer model boundary by clicking the left mouse button: A green line indicates the element edges along which the line geometry will be placed. As the snap distance is used for the selection of ver­tices, make sure that it is large enough for a convenient use of the interpola­tion tool.

In case that you would like to remove the last vertex of a line, place the mouse cursor on top of it and then hit <Del>.

To finish the line and to start the interpolation between the defined values and locations, enter 38 m in the  Editor toolbar, hold <Ctrl> and double-click on a node at the outer model boundary which represents the end of the line. To display the interpolated boundary-conditions values, check the entry  Value Label in Hydraulic-head BC in the  View Components panel.

 

Interpolated boundary conditions.

Additional options to ignore boundary-condition values already assigned along the line geometry during the interpolation process, options for the inter­polation of time-varying data or extrapolation are accessible via  Tools > Global Settings > Tool Properties > Linear 1D Interpolation.

Multilayer-Well Assignment

For this example, it is assumed that the pumping rate is time-constant and that the wells are screened over the entire model depth.

After switching to the Slice view activate  Data panel. In the  Selections panel, set the join-edge selection Well West active with a double-click.

The currently active assignment mode is Multilayer Well which is shown by the Multilayer Well symbol in the input box of the  Editor toolbar. Dou­ble-click into the input box to open the Multilayer Well Editor dialog.

The preview on the right-hand side of the dialog shows the well coordinates and the currently selected join-edges along which the well screen will be placed.

As Capacity, enter a value of 1000 m³/d. For all other parameters we accept the default values. Set the  Assign and leave the dialog with Multilayer Well symbol now indi­cates the position of the specified boundary condition. Use the  Attributes tree in the  View Components panel to display the different attribute val­ues of the  Selections panel, double-click on the stored join-edge selection Well East and open the Multilayer Well Edi­tor dialog again with a click into the input box of the  Editor toolbar. Change the capacity of the well to 500 m³/d and follow the same assign­ment steps as described for the western well.

 

Multilayer Well Editor.

Assignment of Borehole Heat Exchangers

Reload the model parameters.fem to add a Borehole Heat Exchanger (BHE) to the model.

First, open the Problem Settings dialog via  Edit > Problem Settings and switch to Include transport of...  Heat on the Problem Class page. Confirm the changes with  Apply and leave the dialog with OK.

In the  Data panel, activate Boundary Conditions (BC) > Heat transport > Borehole Heat Exchanger with a double-click. In the Selections panel, double click on the stored join-edge selection BHE to set the edges active along which the BHE will be placed.

Borehole Heat Exchanger Dataset Editor.

As a first step, a BHE Dataset has to be created that defines the geometric characteristics of the heat exchanger and also contains the information on the properties of the refrigerant and exchanger components. Double-click on Borehole Heat Exchanger in the input box of the Editor toolbar to enter to the Borehole Heat Exchanger Editor. To add a new dataset, click on Edit borehole heat exchanger datasets and then click on  Add new borehole heat exchanger dataset. This creates the new BHE Dataset #1. Alternatively, the BHE dataset Editor can be accessed via Edit BHE Datasets in the Borehole Heat Exchanger toolbar.

Leave the Double U-shape geometry and only reduce the Borehole Diame­ter to  0.1 m. The geometry change is automatically reflected in the bore­hole sketch at the bottom of the dialog window. For the Heat-transfer coefficients switch from  User-defined to  Computed mode. Confirm the settings and return to the Borehole Heat Exchanger Editor with a click on  OK.

The BHE Data set is now available for assignment and the geometric proper­ties are displayed in the dialog. Two remaining properties need to be defined, the flow rate of the refrigerant within the borehole pipes and also the inlet temperature. Instead of applying a constant inlet temperature, we assign a temperature difference between the inlet and the outlet of the BHE. Switch from  Inlet Temperature to  Temperature Difference and enter a value of  -3° C. Next, enter a Flow Rate of 30 m³/d. For the extent in z-direc­tion leave the setting  From Selected Join Edges. The dialog with all settings is shown in Figure below. Assign the Borehole Heat Exchanger with click on Assign and leave the Editor with OK.

Use' the ' Attributes tree in the  View Components panel to display the different attribute values of the heat exchanger.

 

Borehole Heat Exchanger Editor.

Discrete-Feature Assignment

Reload the model parameters.fem.

On slice 3 we assign some one-dimensional discrete features that represent highly conductive fractures. In the  Selections panel, double-click on the stored slice-edge selection Fractures. We can now go to the Discrete Features panel and open the context menu of Discrete Features. Select  Add Slice-Edge Feature Element > Hagen-Poiseuille.

 

Adding Discrete Features.

The discrete feature is now added to the Discrete Features panel and there is a parameter list is initialized in the  Data panel corresponding to Discrete Features. In the Discrete Features panel, we make a right-click on Feature 1 and open its context menu  Rename. in the context menu of Feature 1. We change the name to Fractures.

To show the discrete feature in the active view, we can double-click on Hydraulic aperture in the Discrete Feature section of the Data panel.

The values for Hydraulic aperture will be edited at all edges belonging to the discrete feature. Double click on Fractures in the Discrete Features panel to activate the target geometry for the assignment.  Enter a value of 1 m in the input box of the  Editor toolbar and click on Assign to complete the operation. Finally click on Clear to de-select the edges.

Discrete Features in the view and Data panel.