Aquaveo & Water Resources Engineering News

Several models in SMS rely on using a 2D mesh. The quality of this mesh can greatly impact your model run and overall results, so here are some tips for making a good quality mesh.

Start with a Good Mesh Generator Coverage

A lot of how well a mesh turns out begins with the mesh generator coverage. Generally, when a poor mesh has been generated, it is because the arcs, vertices, and polygons on the mesh generator coverage did not clearly define a good quality mesh.

When defining the mesh parameters in the coverage, there are few items to keep in mind:

• Make certain the polygons accurately reflect the work area. Do not draw polygons outside of your elevation data.
• Vertices along the arcs determines the size and spacing of elements in the mesh. Adding too few or too many vertices along an arc can cause poor spacing. Using the Redistribute Vertices tool can help with getting the correct number of vertices, and making sure they are evenly spaced along each arc.
• Keep individual arcs smooth and rounded to avoid interior acute angles.
• Use the 2D Mesh Polygon Properties dialog to preview how the final mesh will appear.

Check the Size Transition of the Elements

How elements transition in size can greatly impact how a model uses the mesh. In general, a gradual change in element size functions makes for a better mesh for most models. A poor mesh will have a quick change in elements size, acute interior angles, and thin triangles.

The solution for smoothing out the element transition is to adjust the spacing of the arc vertices in the mesh generator coverage and to examine the proximity of the arcs. In general, arcs that are close to each other should have a similar number of vertices. Arcs that are further apart can have a greater disparity of vertices.

Check For an Even Patch

When creating quadrilateral elements in a mesh using a patch, it is important that the spacing of the vertices be precise. Parallel arcs need to have the same number of vertices when creating a patch or the result will be an uneven patch.

It is recommended to always preview the mesh when using the patch option, then adjust the number of vertices to make certain the patch is even.

Remove Unnecessary Elements

Cleaning up a mesh after it has been generated is sometimes necessary. When generating a mesh from a scatter set or other source, more of the mesh may need to be reviewed and cleaned. Using the Select Thin Triangles command and the Clean command can help with getting rid of unnecessary elements that could cause problems during the model run. It is also recommended to use a mesh with the fewest number of elements needed for your project.

These are only some of the recommended guidelines for generating a good quality mesh. We hope this helps you in your projects.

If you have questions about how to make a better mesh in SMS, contact our technical support for general questions, or contact our consulting services for project-specific inquiries.

Do you have a project that requires modeling a dam, or similar structure, in GSSHA? WMS can make this process smoother with tools designed to help define the structure quickly and efficiently.

In order to create a simulation that includes modeling the dam in WMS and analyzing the dam’s effects using GSSHA, the workflow is as follows:

1. Import an existing GSSHA base model.
2. In the GSSHA map coverage, use the Shift key to select the node where you want the dam to be and the node immediately downstream from it.
3. Right-click on the selected nodes and select Attributes to open a Properties dialog.
4. Select Output Hydrographs at those nodes.
5. Run GSSHA.
6. Using the results from the GSSHA run, size your embankment based on the necessary storage.
7. Using the Create Feature Arc tool, create an arc to represent your dam.
8. Double-click on the arc to bring up the Attributes dialog.
9. Set the type of arc to be an Embankment, then click the ... button next to it to open the Embankment Arc Profile Editor dialog.
1. Set the PVI Elevation to be the height of the dam.
2. Click Compute Vertical Curve to compute the Curve Length.
10. Double-click the node in the stream where your structures will be defined to open the Properties dialog.
11. Click the button under Hydraulic structures to open the GSSHA Hydraulic Structures dialog.
1. Add a Detention Basin, Weir and Culvert.
2. Define the attributes for each of these structures.
12. Run GSSHA again to see the effects of the dam you have created.

If needed, adjust the display options when reviewing the results to get a better idea of how the dam structure affected the results. Try different various options to get a better feel of how the dam affected the simulation results.

Now that you know how to add a dam to GSSHA, try out modeling dam structures and other applications in WMS today!

Parameter estimation using PEST can assist in data interpretation, model calibration, and predictive analysis. PEST can do a lot for your project.

Because PEST offers so much, it can be a little overwhelming to use at first. We provide tutorials and articles on our wiki to help guide you in using PEST with GMS.

In addition to the resources available in the tutorials and wiki, this post covers some useful tips that have helped some of our users.

General PEST Tips

Here are some general tips for troubleshooting PEST in GMS:

• Verify that the parameter key values have been successfully initialized under MODFLOW | Parameters. The key values should match the parameters names. For example, if the key value for hydraulic conductivity is “-30”, the parameter name should be “HK_30”. No key value should be used twice, even across different packages. To continue the example, if you have an “HK_30”, there should not be a “RCH_30”.
• Key values are needed for both zones and pilot points.
• Key values are expected to be negative integers. Non-integers will not be automatically recognized as key values.
• If the key value is not a negative integer, or is a parameter from the WEL package, they will have to be manually added. If you’re missing a value, check that it initialized in the first place.
• Parameters included in the run will be written to the *.param file. Once PEST runs, the optimal values are written to the *.par file.
• If the iterations are giving identical values for the same parameter, check if the value is either the minimum or the maximum of the range assigned to the parameter, then evaluate if that range needs adjusting.
• Adjusting the starting values or the PEST options may help.

Pilot Point Tips

When using PEST and pilot points, consider the following:

• Follow the recommended guidelines found here.
• You can get a quick 2D Scatter set to use for pilot points with the MODFLOW Layers → 2D Scatter Points tool. This is particularly useful for areal parameters, such as HK or RCH.
• If you’re running Null Space Monte Carlo, you must use pilot points and your interpolation method must be set to kriging.
• If running with SVD-Assist, you can point to the Jacobian file so it doesn’t re-solve for every iteration.
• Depending on the parameter, pilot points often should not start with zero values. This especially applies to log transforms.

We hope these tips help and that your project are improved by using PEST with GMS.

SMS allows having multiple simulations for the same project with models such as SRH-2D, ADCIRC, and STWAVE. Furthermore, SMS 13.0 lets you run and manage multiple simulations running at the same time using the new Simulation Run Queue dialog.

The Simulation Run Queue is a modeless dialog, meaning you can continue using SMS while simulations are running. Once a model run has started for a simulation, you are free to start building a new simulation, even one using the existing components. Completed runs may be visualized in SMS while additional runs are still in process.

Functionality

The new Simulation Run Queue dialog functions a little differently from the previous Model Wrapper dialog. Some of the changes include:

• You must click Load Solution to load the desired simulation solution into the project. This does not happen automatically when you click Close as it did before.
• If you try to run a simulation already in the queue, you will be prompted to remove the simulation from the run queue before it can be run again.
• If changing an active simulation’s settings, renaming the active simulation, or taking any action that affects a simulation currently in the queue, you will be asked to remove the simulation from the queue prior to making the changes.

Viewing Plots

With the Simulation Run Queue, diagnostic information—such as monitoring plots—can be displayed during model runs. By turn Monitoring Data off or on, you can watch command line results and residual plots.

Options also exist for changing which plots are displayed in the run queue. Selecting a simulation causes the Plot Options button to appear. In the Plot Options dialog, you can choose which plots to view. You can view Residuals, Monitor Points, and Monitor Lines, and change the options associated with each of these.

Now that you know a little more about the Simulation Run Queue dialog in SMS 13.0, try it out today!