Tutorial 3.04

Tutorial 3.04

4. Flow and transport in a transect to a stream

The most complicated fourth example considers water flow and solute transport in a vertical transect with a stream. The transport domain is relatively complex and consists of objects formed by polylines and splines. The problem, divided into three parts, also demonstrates how results of a previous simulation can be used in follow-up calculations with different boundary conditions or having additional features. At first (A), steady state water flow in the transect towards the stream is calculated. Second (B), a source (e.g., simulating water drainage from waste disposal site) is added to the soil surface about 30 m to the left of the stream for a duration of 100 d. Finally (C), the contaminant source is assumed to be removed after 100 days. Transport of the 100-day solute pulse through the unsaturated zone into groundwater and to the stream is subsequently followed for 1100 days.

1. Steady-state water flow
    
2. Water and contaminant source at the surface
    
3. Plume movement towards a stream

We believe that by carrying out these four examples, HYDRUS users will obtain the basic skills necessary to solve their own two-dimensional problems. We wish you all the luck and patience needed in this endeavor..

1. Water Flow to a Stream 1

Video (52 MB) Download

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

New Project (or File->New Project)
Name: Plume1
Description: Water flow to a stream - 1
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=-100 cm, Xmax=5100 cm, Zmin=-50 cm, Zmax=550 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: 100
Initial Time Step: 0.0001
Minimum Time Step: 0.00001
Maximum Time Step: 5
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: 6
Update
Print Times: 1 5 10 25 50 100
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)
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
Explore Catalog of Soil Hydraulic Properties and Neural Network Predictions
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)
Tab Main: Targeted FE – Size –Automatic with TS = 25 cm
Tab Stretching: Stretching Factor = 3
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 = 100 cm, Distance h = 20 cm
Click on Snap to Grid at the toolbar (or Tools->Snap to Grid)
View->View Stretching: In Z-direction: 5

Define Outer Boundary
Select the Line-Polyline command from the Edit Bar (or Insert->Domain Geometry->Lines->Polylines->Graphically)
Select the Spline command from the Edit Bar (or Insert->Domain Geometry->Lines->Splines->Graphically)

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=10.0 cm.
Alternatively select FE-Mesh from the Navigator Bar and Insert Mesh Refinement from the Edit Bar and specify Finite Element size S=10.0 cm.
After clicking OK, select all nodes at the top of the transport domain.
Click Generate FE-Mesh from the Edit Bar (or Edit->FE-Mesh->Generate FE-Mesh)

Click on View All at the toolbar (or View->View All)

Water Flow Initial Conditions:
On the Navigator Bar click on Initial Conditions – Pressure Head (or Insert->Initial Conditions->Pressure Head)

1. Select the entire transport domain between x=0 cm and 4700 cm.
   Click on the Set Value command at the Edit Bar, check Equilibrium from the lowest located nodal point, set equal to 400 cm (Bottom Pressure Head Value), and check Slope in the x-direction = -2.8o.
2. Select the entire transport domain between x=4600 cm and 500 cm.
   Click on the Set Value command at the Edit Bar, check Equilibrium from the lowest located nodal point, set equal to 175 cm (Bottom Pressure Head Value), and check Slope in the x-direction = 2.4o.

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

1. Select Constant Head from the Edit Bar, select the left side boundary, and specify 400 cm with Equilibrium from the lowest located nodal point.
2. Select Constant Head from the Edit Bar, select the right side boundary, and specify 190 cm with Equilibrium from the lowest located nodal point.
3. Zoom on the stream. Select Constant Head from the Edit Bar, select all nodes with the z-coordinate smaller than 175 cm, and specify 80 cm with Equilibrium from the lowest located nodal point.
4. Zoom on the slope left of the stream. Select Seepage Face from the Edit Bar and select all nodes with the z-coordinate smaller than 300 cm,

Default View.

Menu: File->Save (or from Toolbar)

Menu: Calculation->Run HYDRUS (or from Toolbar)
(Execution time on 3 GHz PC – 10 s) OUTPUT:
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 different display modes using Options->Graph Type

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

2. Water Flow and Solute Transport to a Stream 2

Video (26 MB) - Download

Add the source at the soil surface: Close the Plume1 Project (click Save Project at the Toolbar or File->Save)

Project Manager (File->Project Manager)
Select the Plume1 project
Button “Copy”
Name: Plume2
Description: Water flow and solute transport to a stream - 2
Button “OK”

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

Solute Transport - General Information (Edit->Flow and Transport Parameters->Solute Transport Parameters->General Information)
Select GFE with artificial dispersion
Button “Next”

Solute Transport - Transport Parameters (Edit->Flow and Transport Parameters->Solute Transport Parameters-> Solute Transport Parameters)
Diffus. W. = 3
Disp.L = 10
Disp.T = 1
Button “Next”

Solute Transport - Reaction Parameters (Edit->Flow and Transport Parameters->Solute Transport Parameters-> Solute Reaction Parameters)
CBound1=0
Cbound2=1
Button “Next”

Water Flow Initial Condition:
Import the final pressure head profile from Plume1 as the initial condition for Plume2 (Edit->Initial Conditions->Import)
Find project Plume1
Select Pressure Head and click OK
On the Navigator Bar click Initial Condition.

Water Flow and Solute Transport Boundary Conditions:

1. On the Navigator Bar click on Boundary Conditions – Water Flow.
   Zoom on the soil surface with x=16-17 m.
   Select Constant Head from the Edit Bar, select the top four nodes between x=16 and 17 m, and specify h=0 cm.
2. On the Navigator Bar click on Boundary Conditions – Solute Transport.
   Select Third-Type from the Edit Bar, select the top nodes between x=16 and 17 m, specify Pointer to the Vector of Boundary Conditions = 2.

Menu: View->View All (or from Toolbar)

Menu: File->Save (or from Toolbar)

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

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 different display modes using Options->Graph Type

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.

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

3. Water Flow and Solute Transport to a Stream 3

Video (34 MB) - Download

hange boundary condition after 100 d of simulation:

Close the Plume2 Project (click Save Project at the Toolbar or File->Save)

Project Manager (File->Project Manager)
Select the Plume2 project
Button “Copy”
Name: Plume3
Description: Water flow and solute transport to a stream - 3
Button “OK”

Time Information (Edit->Flow and Transport Parameters->Time Information)
Time Units: days
Initial time: 100
Final time: 1200
Initial Time Step: 0.001
Minimum Time Step: 0.00001
Maximum Time Step: 50
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: 11
Update
Default
Button “Next”

Water Flow and Solute Transport Initial Condition:
Import the final pressure head profile from Plume2 as the initial condition for Plume3 (Edit->Initial Conditions->Import)
Find project Plume2
Select Pressure Head and Concentrations and click OK
On the Navigator Bar click Initial Condition.

Water Flow and Solute Transport Boundary Conditions:
On the Navigator Bar click on Boundary Conditions – Water Flow.
Select Constant Flux from the Edit bar and assigned it to all nodes at the soil surface between the seepage face and the left side, and between the stream and the right side; and specify a flux=0.05 cm/d.

Observation Nodes
On the Navigator Bar click on Domain Properties – Observation Nodes.
Click on Insert at the Edit Bar and specify 5 points arbitrarily between the source and the stream.

Menu: View->View All (or from Toolbar)

Menu: File->Save (or from Toolbar)

Menu: Calculation->Run HYDRUS (or from Toolbar)
(Execution time on 3 GHz PC – 195 s)

OUTPUT:
Menu: Post-Processing ->Observation Points: Concentrations
Menu: Post-Processing ->Time Information: Peclet Numbers
Menu: Post-Processing ->Boundary Information->Solute Fluxes: Constant Boundary Flux
Menu: Post-Processing ->Mass Balances Information
Menu: Post-Processing -> Graphical Display of Results
Concentrations