Tutorial 3.02

Tutorial 3.02

Subsurface Line Source

The example in this computer session considers a subsurface line source (e.g. drip irrigation) of water (first without and then with a solute) in a vertical cross-section. The (x, z) transport domain is 75 x 100 cm2, with the source located 20 cm below the soil surface on the left boundary of the transport domain. Infiltration is initiated with a variable flux boundary condition and is maintained for 1 day, with the duration of the solute pulse being 0.1 days; with 2 cycles per week. An unstructured finite element mesh is generated using the Meshgen-2Dprogram. The example is again divided into two parts: first only water flow is considered, after which solute transport is added. This example will familiarize users with the basic concepts of transport domain design in the graphical environment of HYDRUS, with boundaries and domain discretization, and with the graphical display of results using contour and spectral maps.

A. Infiltration of Water From a Subsurface Source

Video (45 MB) - Download
Download Project Source1.zip (0,4 MB)

Project Manager (File->Project Manager) Button “New”

New Project (or File->New Project)
Name: Source1
Description: Infiltration of Water from a Subsurface Source
Working Directory: Temporary – is deleted after closing the project
Button “Next”

Geometry Information (Edit->Domain Geometry->Geometry Information)
Type of Geometry: 2D Vertical Plane
Domain Definition: General
Units: cm
Initial Workspace: Xmin=-25 cm, Xmax=100 cm, Zmin=-25 cm, Zmax=125 cm (to accommodate the transport domain)
Button “Next”

Main Processes (Edit->Flow and Transport Parameters->Main Processes)
Check Box: Water Flow Button “Next”

Time Information (Edit->Flow and Transport Parameters->Time Information)
Time Units: days
Final Time: 7
Initial Time Step: 0.0001
Minimum Time Step: 0.000001
Maximum Time Step: 5
Time Variable BC: Check
Number of Time-Variable BC: 4
Button “Next”

Output Information (Edit->Flow and Transport Parameters->Output Information)
Print Options:
Check T-Level Information
Check Screen Output
Check Press Enter at the End
Print Times: Count: 14
Print Times: 0.1, 0.25, 0.5, 0.75, 1, 1.5, 2, 3.5, 3.6, 3.75, 4, 4.5, 5.5, 7 d
Update
Button “Next”

Water Flow - Iteration Criteria (Edit->Flow and Transport Parameters->Water Flow Parameters->Output Information)
Leave default values as follows:
Maximum Number of Iterations: 10
Water Content Tolerance: 0.001
Pressure Head Tolerance: 1
Lower Optimal Iteration Range: 3
Upper Optimal Iteration Range: 7
Lower Time Step Multiplication Factor: 1.3
Upper Time Step Multiplication Factor: 0.7
Lower Limit of the Tension Interval: 0.0001
Upper Limit of the Tension Interval: 10000
Initial Condition: In the Pressure Head
Button “Next”

Water Flow - Soil Hydraulic Model (Edit->Flow and Transport Parameters->Water Flow Parameters ->Soil Hydraulic Model)
Leave default values as follows:
Radio button - van Genuchten-Mualem
Radio button - No hysteresis
Button “Next”

Water Flow - Soil Hydraulic Parameters (Edit->Flow and Transport Parameters->Water Flow Parameters ->Soil Hydraulic Parameters)
Leave default values for loam
Button “Next”

Variable Boundary Conditions (Edit->Flow and Transport Parameters->Variable Boundary Conditions)

Time	Transp	Var.Fl1 (variable flux)
1.0	0	-60 (drip discharge distributed over the circumference of the drip)
3.5	0	0
4.5	0	-60
7	0	0

Button “Next”

FE-Mesh - FE-Mesh Generator (Edit->FE-Mesh->FE-Mesh Generator)
Radio button - Meshgen
Button “Next”

FE-Mesh - FE-Mesh Parameters (Edit->FE-Mesh->FE-Mesh Parameters)
Targeted FE – Size – Unselect Automatic and specify TS = 5 cm
Button “OK”

Definition of the Transport Geometry
Click on Grid and Work Plane Setting at the toolbar (or Tools->Grid and Work Plane)
Grid Point Spacing – Distance w = 1 cm, Distance h = 1 cm
Click on Snap to Grid at the toolbar (or Tools->Snap to Grid)

a) Outer Boundary
Select the Line-Polyline command from the Edit Bar (or Insert->Domain Geometry->Lines->Polylines->Graphically)
Nodes coordinates: (0,79), (0,0), (75,0), (75,100), (0,100),(0,81) b) Drip
Zoom at the source.
Select the Arc via Three Points command from the Edit Bar (or Insert->Domain Geometry->Lines->Arc->Graphically->Three Points) and specify coordinates of three points: (0,81), (1,80), (0,79)
View All (View->View All).

Define the Base Surface
Domain Geometry->Surface->Graphically and click at the outer boundary
Alternatively select the Surface via Boundaries command from the Edit Bar and click at the outer boundary

Define FE-Mesh
Insert->FE-Mesh Refinement->Graphically: a dialog appears in which specify Finite Element size S=0.5 cm
After clicking OK, select three nodes defining the drip at the left side.

Click on the Insert Mesh Refinement at the Edit Bar, click New, and specify Finite Element Size = 2 cm. Assign this refinement to the node at the top left corner.

Click Generate FE-Mesh from the Edit Bar (or Edit->FE-Mesh->Generate FE-Mesh)

Specify Initial Condition:
On the Navigator Bar click on Initial Conditions – Pressure Head (or Insert->Initial Conditions->Pressure Head)
Select the entire transport domain
Click on the Set Value command at the Edit Bar, and set equal to -400 cm (Pressure Head Value).

Water Flow Boundary Conditions:
On the Navigator Bar click on Boundary Conditions – Water Flow (or Insert->Boundary Conditions->Constant Head)
Zoom on source: (0,80)

1. Select Variable Flux 1 from the Edit Bar and assign it to the arc Click on View All at the toolbar (or View->View All)
2. Select Free Drainage from the Edit Bar and assign t points at the bottom of the soil profile

Observation Nodes
On the Navigator Bar click on Domain Properties – Observation Nodes (or Insert->Domain Properties->Observation Nodes)
Click on the Insert command on the Edit Bar and specify 5 points arbitrarily in the transport domain between source and drain

Menu: File->Save (or from Toolbar)

Menu: Calculation->Run HYDRUS (or from Toolbar)
(Execution time on 3 GHz PC – 18 s)

OUTPUT:

Results – Other Information: Observation Points (from the Navigator Bar, or Results->Observation Points from menu)
Pressure Heads
Water Contents

Results – Other Information: Boundary Fluxes (from the Navigator Bar, or Results->Boundary Information->Boundary Fluxes from menu)
Variable Boundary Flux
Free Drainage Boundary Flux

Results – Other Information: Cumulative Fluxes (from the Navigator Bar, or Results->Boundary Information->Cumulative Fluxes from menu)
Variable Boundary Flux Results – Other Information: Mass Balance Information (from the Navigator Bar, or Results->Mass Balance Information from menu)

Results – Graphical Display: Pressure Heads (from the Navigator Bar, or Results->Display Quantity->Pressure Heads from menu)
Use Listbox Time Layer or Slidebar on the Edit Bar to view results for different print times
Check Flow Animation
Select Boundary Line Chart from the Edit Bar and draw pressure heads for one vertical column
Select Cross Section Chart and draw pressure heads through the middle of the column
Select different display modes using Options->Graph Type

Results – Graphical Display: Water Contents (from the Navigator Bar, or Results->Display Quantity->Water Contents from menu)

Results – Graphical Display: Velocity Vectors (from the Navigator Bar, or Results->Display Quantity->Velocity Vectors from menu)

B. Infiltration of Water and Solute From a Subsurface Source

Video (41 MB) - Download
Download Project Source2.zip (0,6 MB)

Close the Infiltr1 Project (click Save Project at the Toolbar or File->Save)

Project Manager (File->Project Manager)
Select the Source1 project
Button “Copy”
Name: Source 2
Description: Infiltration of Water and Solute from a Subsurface Source
Button “OK”

Main Processes (Edit->Flow and Transport Parameters->Main Processes)
Check Box: Solute Transport Button “OK”

Solute Transport – General Info (Edit->Flow and Transport Parameters->Solute Transport Parameters->General Information)
Leave default values
Button “Next”

Solute Transport - Solute Transport Parameters (Edit->Flow and Transport Parameters->Solute Transport Parameters->Solute Transport Parameters)
Leave the default values
Bulk Density = 1.5 cm3/g
Disp.L = 2 cm
Disp.T = 0.2 cm
Diff.=0
Button “Next”

Solute Transport - Transport Parameters (Edit->Flow and Transport Parameters->Solute Transport Parameters->Solute Reaction Parameters)
Leave the default values for tracer
Note that cBnd in Boundary Conditions is equal to 1 (this is boundary concentration)
Button “Next”

Variable Boundary Conditions (Edit->Flow and Transport Parameters->Variable Boundary Conditions)
Click on Time 1 and click add line
Click on Time 4.5 and click add line

Time	Transp	Var.Fl.1	cValue1
0.1	0	-60	1
1.0	0	-60	0
3.5	0	0	0
3.6	0	-60	1
4.5	0	-60	0
7	0	0	0

Button “Next”

Specify Initial Condition:
Import the final pressure head profile from Source1 as the initial condition for Source1 (Edit->Initial Conditions->Import)
Find project Source1
Select Pressure Head and click OK
On the Navigator Bar click Initial Condition.

Menu: Calculation->Run HYDRUS (or from Toolbar)
(Execution time on 3 GHz PC – 50 s)

OUTPUT:

Results – Other Information: Solute Fluxes (from the Navigator Bar, or Results->Boundary Information->Solute Fluxes from menu)
Variable Boundary Flux
Free Drainage Boundary Flux

Results – Graphical Display: Concentrations (from the Navigator Bar, or Results->Display Quantity->Concentrations from menu)
Click with the right mouse button on the color scale and from the pop-up menu click on Min/Max Global in Time. See how the display changed.