Tutorial 2
Building a multi-layer heterogeneous, anisotropic model with various boundary conditions
Introduction
This second tutorial builds on the model created in the first tutorial. The first tutorial model was two-dimensional and steady, but this second tutorial will guide you through creating a model that has a multi-layer three-dimensional (3D) region in an area near the middle reach of the river. The well will be changed from fully-penetrating to partially-penetrating. This model may be built with the Demo version of Anaqsim, and will contain two levels in the multi-level region. More levels are possible with the Deep Designer licensed version of Anaqsim and there is some instruction about that at the end of the tutorial.
Opening the First Tutorial Model
Either begin with the model you had after competing the first tutorial, or download and then open the following file tutor1.anaq from Anaqsim. To open the file in Anaqsim, select File / Open from the main menu, then locate and open the tutor1.anaq file. Next select File / Save As and save this under another name such as 'tutor2.anaq'.
Zoom in on the area where you will make the model multi-level (2D) so that the resulting view looks something like the following image. In this case, the basemap (available in the C:\Program Files\Yellow Sub Hydro\Anaqsim\Documentation folder) is displayed in gray. The model elements are displayed in green.
Adding New Domains for the Multi-Layer Area
In the area near the well and the middle river reach (h=144 to h=108), we will create a region with two levels instead of one. The first step is to create new domains for this region. Select Model Input / Domains / Confined and/or Unconfined to bring up the domains data table, which contains two domains 'all' for most of the model, and 'recharge basin' for the recharge basin area. These two domains have the same properties, but differing recharge rates.
We will add 2 new domains for the multi-level region. The quickest way to create the new rows is to duplicate the two existing rows. Select both existing rows as is shown below.
Then right-click and choose Copy Selected Rows and then right-click and select Paste New Rows. Edit the first 5 columns of the new rows so that they look like the following table. Columns 6+ will all be unchanged, since these domains all have the same properties, just different elevations.
Note that the bottom elevation of the new two-level area is 80, a bit lower than the bottom elevation of the 'all' domain at 82. This is just to show that elevations may change laterally in a model if you want them to. The '3D upper' domain is in level 1 and is unconfined with a base at elevation 95. The '3D lower' domain is in the 2nd level (level numbers increase with depth) and is confined with a constant saturated thickness of 15, going from elevation 80 to 95.
At this point, save your model with File / Save from the main menu or Ctrl-S.
Interdomain Line Boundary to Define the 3D Region
We have defined the two new domains that will apply in the 3D region, but still need to define the area where those domains exist. Anaqsim does this with external line boundaries that refer to the domains. In this case, we will create one new interdomain line boundary that will represent the lateral transition from the single-level 'all' domain to the multi-level 3D area. At interdomain boundaries, the conditions imposed are continuity of flow and continuity of head across the boundary.
First digitize the interdomain boundary. Select the Plot tab, and make sure that under the plot menu Snap Settings / Snap to Elements is checked. This allows the digitized interdomain line boundary to 'snap to' the same vertex coordinates as the river line boundaries. When the cursor moves over an existing vertex, an orange box will appear; if you click with the orange box showing, it will snap to the same coordinates. Digitize a closed polygon boundary like the yellow one shown below, making sure to snap to the river vertexes labeled 'h=114' and 'h=108'. You can go around the boundary in either clockwise or counter-clockwise order, but it is important to remember which way you went.
Next, select Model Input / Line Boundaries / Inter-Domain and add a new row so it looks like this:
The 'ID' boundary defined the limits of the recharge basin, and the new '3D limits' one will define the boundary of the 3D area. Click on the Edit button in the '3D limits' row and paste in the coordinates you just digitized, and then press OK.
Then, click on the Select button under Domains_left. If you digitized in clockwise order, select the 'all' domain and if you digitized in counter-clockwise order, select both '3D Upper' and '3D Lower'. Imagine walking on the ground surface along the line you just digitized; Domains_left would be to your left as you walk along the boundary and Domains_right would be to your right. This interdomain boundary makes a transition from two levels (3D upper, 3D lower) on one side to a single level (all) on the other. By doing this, interdomain boundaries can help you efficiently concentrate computing power and multiple levels in a limited area. Interdomain boundaries can also join a single domain on one side with a single domain on the other side.
Now click on the Select button under Domains_right. If you digitized in clockwise order, select both '3D Upper' and '3D Lower' and if you digitized in counter-clockwise order, select the 'all' domain.
To check your input, select Make Plot / Model Elements Only, then select level 1 and press OK, and you should see something like this in the area near the well.
The new interdomain line boundary is now green, since it is composed of elements in the model. Move the cursor over the vertexes of the interdomain line boundary to check that the left/right sense of the domains is correct. Move the mouse across the boundary, and observe the domain listed at the left. When you are outside the 3D area, you should see this:
When you are inside the 3D limits you should see this:
Now make a similar plot, but chose level 2 instead of level 1 and you will see something like this:
The river elements do not show up, since they are in level 1. Move the mouse across the boundary, and observed the domain listed at the left. When you are outside the 3D area, there is no level 2 and you should see a blank under Domain Name:
When you are inside the 3D limits you should see this:
