2-2 GMS Tutorials Volume II
You can e if the components are enabled by lecting the File | Register
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command.
一分米等于多少毫米2.2 Description of Problem
The problem we will be solving in this tutorial is shown in Figure 2-1. This
problem is a modified version of the sample problem described near the end of the
MODFLOW Reference Manual. Three aquifers will be simulated using three
layers in the computational grid. The grid covers a square region measuring
75000 ft by 75000 ft. The grid will consist of 15 rows and 15 columns, each cell
measuring 5000 ft by 5000 ft in plan view. For simplicity, the elevation of the top
and bottom of each layer will be flat. The hydraulic conductivity values shown
are for the horizontal direction. For the vertical direction, we will u some
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fraction of the horizontal hydraulic conductivity.
Flow into the system is due to infiltration from precipitation and will be defined
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as recharge in the input. Flow out of the system is due to buried drain tubes,
discharging wells (not shown on the diagram), and a lake which is reprented by
a constant head boundary on the left. Starting heads will be t equal to zero, and
a steady state solution will be computed.
Figure 2-1 Sample Problem to be Solved.
2.3 Getting Started
Let s get started.
MODFLOW - Grid Approach 2-3
1.If necessary, launch GMS. If GMS is already running, lect the File |
New command to ensure that the program ttings are restored to their
default state.古风高清壁纸
2.4 Units
At this point, we can define the units ud in the model. The units we choo will
be applied to edit fields in the GMS interface to remind us of the proper units for
each parameter.
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1.Select the Edit | Units command.
2.For Length, enter m (for meter). For Time, enter d (for days). We will
ignore the other units (they are not ud for flow simulations).
3.Select the OK button.
2.5 Creating the Grid
The first step in solving the problem is to create the 3D finite difference grid.
1.In the Project Explorer right-click on the empty space and then, from the
pop-up menu, lect the New | 3D Grid command.
2.In the ction entitled X-dimension, enter 22860 for the Length value, and
15 for the Number cells value.
3.In the ction entitled Y-dimension, enter 22860 for the Length value, and
15 for the Number cells value.
4.In the ction entitled Z-dimension, enter 4570 for the Length value, and 3
for the Number cells value.
Later, we will enter the top and bottom elevations for each layer of the grid.
Thus, the thickness of the cells in the z directions you enter here will not affect the
MODFLOW computations.唯美成语
5.Select the OK button.
The grid should appear in your window in plan view. A simplified reprentation
of the grid should also appear in the Mini-Grid Plot.
Figure 2-2 Mini-Grid Plot
2-4 GMS Tutorials Volume II
2.6 Creating the MODFLOW Simulation
The next step in tting up the model is to initialize the MODFLOW simulation.
1.In the Project Explorer right-click on the 3D Grid Data folder
MODFLOW - Grid Approach 2-5 of -1 for each of the thirty constant head cells. However, there is another way to edit the IBOUND array that is much simpler for this ca. This method will be described later in the tutorial. For now we will leave all of the cells active.
2.Select the OK button to exit the IBOUND dialog.
Starting Heads
The next step is to t up the Starting Heads array.
1.Select the Starting Heads button.
The Starting Heads array is ud to establish an initial head value when performing a transient simulation. Since we are computing a steady state simulation, the initial head for each cell shouldn't make a difference in the final solution. However, the clor the starting head values are to the final head values, the more quickly MODFLOW will converge to a solution. Furthermore, for certain types of layers, if the starting head values are too low, MODFLOW may interpret the cells as being dry. For the problem we are solving, an initial value of zero everywhere should suffice.
The Starting Heads array is also ud to establish the head values associated with constant head cells. For our problem, the constant head values are zero. Since all of the starting head values are already zero by default, we don't need to make any changes.
2.Select the OK button to exit the Starting Heads dialog.
Top and Bottom Elevations
The next step is to t up the top and bottom elevation arrays.
1.Select the Top Elevation button.
2.Make sure the Layer is 1.
3.Select the Constant Layer button.
4.Enter a value of 60 and lect the OK button.
最厉害的招聘话术5.Select the OK button to leave the Top Elevations dialog.
GMS forces the top of a layer to be at the same location as the bottom of the layer above. Thus, we only need to enter the bottom elevations of all the layers now and the tops of the layers will be t automatically.
6.Select the Bottom Elevation button.
7.Make sure the Layer is 1.
2-6 GMS Tutorials Volume II
8.Select the Constant Layer button.
9.Enter a value of -45 and lect the OK button.
10.Change the Layer to 2.
11.Select the Constant Layer button.
12.Enter a value of -120 and lect the OK button.
13.Change the Layer to 3.
14.Select the Constant Layer button.
15.Enter a value of -215 and lect the OK button.
16.Select the OK button to exit the Bottom Elevation dialog.
17.Select the OK button to exit the MODFLOW Global Package dialog.
2.7 Assigning IBOUND Values Directly to Cells
As mentioned above, the IBOUND values can be entered through the IBOUND
Array dialog. In some cas, it is easier to assign values directly to cells. This
can be accomplished using the Cell Properties command. Before using the
command, we must first lect the cells in the leftmost column of the top two
layers.
2.7.1 Viewing the Left Column
To simplify the lection of the cells, we will change the display so that we are
viewing the leftmost layer.
1.Choo the Side View button
.
3.Change the Z magnification to 15.
4.Select the OK button.
2.7.2 Selecting the Cells
To lect the cells:
