GMS

Converting a 3D UGrid in GMS

By aquaveo on May 9, 2023

Have you ever had an unstructured grid (UGrid) or mesh in your project in the Groundwater Modeling System (GMS) that you want to convert to another geometry? While there isn't a specific tool for converting UGrids in GMS, it can still be achieved by following a few simple steps. Typically a UGrid will need to be converted to a scatter set and from there the scatter set can be converted to other geometries. Converting UGrids or mesh into scatter points can be a good way to compare data between models, especially if one of the models is older and doesn't, or can't, include a UGrid or mesh. If this is something that interests you, this article will explain how to get from a UGrid or mesh to either 2D or 3D scatter points.

First, go to the Display menu above the macros in the GMS window. Then choose Convert to CAD. Note: CAD data. is generated from whatever is currently visible in the Graphics window, so make sure that everything you need is displayed before you continue. The new CAD data will appear in the project window as a (*.dwg) file. Now right-click on the CAD data and convert CAD Points to TIN Points. A dialog window will appear asking you to designate which layers of the data you want to include in the conversion and to name the new TIN. You can customize this in whichever way best suits your needs.

This new TIN data can be converted directly into a scatter set. Right-click on the TIN and convert it into a 2D scatter set. 3D scatter sets can be made by simply executing a conversion one more time with the 2D scatter set.

If ultimately you want to compare scatter data with another model, it may be helpful to be able to view both sets of data in the same window. You can easily export the scatter set from GMS by right-clicking on the scatter set in the project window and selecting Export, then open the newly exported file in the GMS window with your other project. The scatter set can also be used to create a boundary for a 2D or 3D Cartesian grid which could be used with an older version of MODFLOW.

Head over to GMS and try converting UGrids into scatter sets today!

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Exploring the MODFLOW HUF Package

By aquaveo on April 18, 2023

Are you looking to control flow between grid cells in your MODFLOW project using the Ground-water Modeling System (GMS)? MODFLOW offers a couple packages for doing this, but consider using the Hydrogeologic-Unit Flow (HUF) package. This package gives you greater control over the properties of cells regulating flow in a MODFLOW model and help represent more complex stratigraphy in your project.

The HUF package is located in the MODFLOW Global options, and can be used in conjunction with other packages. The HUF package is one of the flow packages, of which you can only have one flow package selected for a project. Once the HUF package has been added to the project, it can be accessed through the MODFLOW menu.

The benefit of using the HUF package in your MODFLOW model is that the materials are not bound to the grid, making it possible for there to be more than one material mapped to a single cell. The hydrogeologic units are calculated independent of the cell boundaries, so by using the HUF package the model can more accurately represent the relationship between materials.

View the hydrogeologic units by going to the display options and clicking on the MODFLOW tab under 3D Grid Data, then turn on Hydrogeologic units. Back in the Graphics Window, when in ortho mode, you can view the model from the top, front, or side.

By accessing the HUF package under the MODFLOW menu, you can select the Edit Materials button to view or change the conductivity level of each material. In the HUF package dialog, you can also edit the top values or thickness values in the array manually, and designate whether to use vertical hydraulic conductivity (VK) or vertical anisotropy (VANI). You can also define each layer as confined or convertible, assign a head to dry cells, adjust grid elevations, and more. The HUF arrays can also be exported to grid datasets, which makes them viewable as contours or in a table.

Incorporating the HUF package into GMS also expands how the package can be used. For example, GMS has the ability to use TPROGS to generate HUF data.

Go to GMS and see how the HUF package can be used in your MODFLOW model today!

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Setting Up a Cross Section Animation in GMS

By aquaveo on March 28, 2023

Have you ever wanted a way to better visualize cross sections in your project? The Animation Wizard in the Ground-water Modeling System (GMS) can help you do just that. Any project involving a 3D mesh or 3D grid can utilize the cross section animation feature.

To build your initial cross section, you’ll need to start with a 3D mesh or grid as a foundation. After your foundation is set, build the cross section. Keep in mind that the Animation Wizard will create the animation through what is currently visible in the Graphics Window, so it is a good idea to get the display settings where you want them before starting the animation process.

Go to the Display menu and scroll down to the bottom to find the Animate option. Before initiating the animation, make sure that the cross section is active in the Graphics Window. Note that although the cross section needs to be active to create the animation, it doesn’t need to be turned on if you don’t want the static cross section from the project to be visible.

Example of the setting up a cross section animation in GMS

In the Animation Wizard dialog, turn on Cross-sections/Isosurfaces under Steady State. This is the option that animates the cross sections. You can change the speed of the animation by altering the number of frames per second, which is on the first page of the Animation Wizard, and the number of frames, which is on the second page. The lower the number of frames per second, the longer the animation will spend on each cross section, and vice versa.

The second page of the Animation Wizard is where you can specify the plane over which the cross sections will be animated. You can animate over the X, Y, or Z-axis, or any combination of the three. You can also alter more of the display options for the animation under the Cross Section Option button on this page.

After clicking Finish, the Animation Wizard will automatically export the cross section animation as an MP4 file, and you can open the MP4 file to view the finished product.

Even more settings and options are available that were not covered in this post, explore what cross section animations can do for your GMS project today!

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Using Bias When Creating a 3D Grid

By aquaveo on March 7, 2023

Sometimes when creating a 3D grid in the Ground-water Modeling System (GMS) you may want to include a bias in the grid for your project. Using a bias parameter will refine part of the grid along a particular axis. Here are some important things to know when implementing a bias into the grid.

All of the data fields necessary for this function will be in the Create Finite Difference Grid dialog window, which appears when a new grid is created. It is here that you can customize the X, Y, and Z-Dimensions to include your bias. The starting point for the bias is determined by the cell number designated in the Origin field of each dimension, and the bias will run along the axis in the positive direction. You can input a different value for the bias in each of the dimensions.

Example of the Create Finite Difference Grid dialog showing the bias option

For a value greater than one in the bias field, each cell will be a percentage larger than the one previous. For example, a bias of 1.2 will mean that each cell following the origin is 20 percent larger than the one previous. These cells will grow in the positive direction along the axis. To make each cell following the origin smaller than the one previous rather than larger, make the bias less than one. For example, a bias of 0.8 will mean that each cell will be 80 percent of the size of the previous cell.

The length field in each of the dimensions determines the total length of the dimension. All of the cells on that axis will fit inside that measurement. After specifying a length, there are two options for how GMS will calculate the size of the cells including the bias. First is by the number of cells in each axis. The grid creator will calculate how big each of the cells must be in order to fit that number into the specified length.

The second option for determining cell size is to input a value for the dimension of the starting cell. For example, setting the cell size to 10 feet will tell the grid creator that the origin cell should be 10 feet, and each cell following should be a percentage larger than the origin cell until the entire length of the axis is filled. This can be refined even farther by specifying a cell size limit, keeping a cell from growing larger than a specified size. Because of this, the cell size limit should be set to a number larger than the base cell size.

With GMS, there are many ways to customize a 3D grid. Give the grid bias function in GMS a try today!

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