SMS

Best Practices for 2D Hydraulic Modeling

In SMS, designing a good 2D hydraulic model from the start gives the best results. A poorly designed model can give bad results, cause model errors, or even keep the model from converging. And while it may seem easy at first to design a good model, there are plenty of potential pitfalls that can come up if you are not careful.

The following tips, broken down into five areas, can help improve any model.

Terrain Data

Pay attention to your terrain data. You can't set up a good model without a good foundation, and terrain data is your foundation. There are four things you will need to spend time getting right:

  • Represent hydraulic controls accurately
  • Make sure you include channel bathymetry
  • Add breaklines where needed
  • Finally review the terrain surface for missing features
Terrain review
Mesh Development

Use an appropriate number of elements: size does matter, more is not always better. This is mainly because the time your model takes to render is a significant factor for any project. Element length should generally be equal to or greater than the flow depth, except for limited areas such as piers. When elements are too small, waves can form skewing the model results.

Quadrilatereal elements in meshes are often more stable than when using triangular elements. Once you have set your number of elements and length, confirm that hydraulic controls are represented in the mesh.

Lastly, review your mesh for quality.

Mesh quality review
Boundary Conditions

When determining the boundaries of your model, you will need to find two things. First look for the most constricted area when determining model limits. Second, find the furthest usable boundary location from the area of interest. A good rule of thumb for rivers: two floodplain widths up and downstream. Note that the width of the mesh should be greater than the maximum flood width.

Lastly, perform sensitivity analysis on boundary conditions.

Material Roughness

Be aware that Manning's n values for 2D model can be lower than 1D models. Be sure to calibrate your model. Essentially check your results to see if they are reasonable.

Model Execution and Review
  • Use the largest time step possible that gives you continuity and stability ( i.e. while still achieving a good solution).
  • Use monitoring points to verify steady simulation.
  • Use monitoring lines to verify continuity.
  • Review convergence parameters to confirm conservation of mass.

Following these tips can improve any model that uses a 2D mesh. Try them out in SMS today!

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Using the Prune Arc Tool

The Prune Arc tool is relatively new to SMS, and we're excited to show you just how useful it can be.

The Prune Arc tool is similar to the smooth arc function in SMS. This Smooth Arc tool is useful when eliminating noise from a rough arc, and can make your variations more mathematically stable. This can be extremely handy in working with a model—especially in situations like coastal modelling, which are prone to busy edges. Unfortunately, smoothing an arc can also change the shape of the arc to the point where it no longer matches the actual coastline.

You may come across a situation where your imported arcs have a lot of unnecessary roughness or concave areas that you want to eliminate without redistributing your vertices along the rest of the arc.

If this is the case, the Prune Arcs function is just the tool for the job. This tool trims—or prunes—rough edges and outlying spikes without rounding or reshaping the rest of the arc. Specifically, it allows you to focus on smoothing one side of the arc. This is helpful in coastal modeling where there may be a small river mouth, a harbor, cove or other concave sections that you do not want to include in your model.

Prune arc example

Access the Prune Arc tool by doing the following:

  1. Use the Select Feature Arcs tool to choose the arc or arcs you wish to prune.
  2. Right-click on the selected arcs then, in the menu, select the Prune Arc(s) command.

This will bring up the Prune Arcs dialog box, from which you can choose your pruning settings.

There are two types of pruning that can be done: Constant and Spatially Varying.

  • Constant will prune everything within a specific measurement set by you. This measurement is in meters by default. The larger the number, the more dramatic the pruning will be.
  • Spatially Varying uses the numbers in a particular dataset to establish the parameters of the pruning. This dataset is chosen in the Prune Arcs dialog box.

Importantly, you must choose which side of the arc to prune. The sides of the arc are determined by the arc direction. So if the arc is moving south to north, the left side of the arc will be on the left side of your screen. If the arc is moving west to east, the left side with be towards the top of your screen. Make certain you are pruning the correct side of the arc.

Try out using the Prune Arc tool in SMS 13.0 today!

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Converting a 2D Scatter to a Raster

Have you ever needed to convert a 2D scatter set to a raster? A new feature of SMS 13.0 allows converting a 2D scatter set to a raster from the right-click menu in the Project Explorer.

Being able to convert from a 2D scatter set to a raster is particularly useful when collaborating with a colleague, or switching between programs. There are many types of raster files that can be shared between different applications.

To convert a 2D Scatter right-click on the 2D Scatter Set under Scatter Data folder in the Project Explorer and go to Convert | Scatter → Raster.

In the Interpolate to Raster dialog you have three options for Interpolation:

  • Linear
  • Inverse Distance Weighted
  • Natural Neighbor

Each option for interpolation is slightly different from the other focusing more on lower z values, higher z values, or the x and y values. Feel free to compare all three with your 2D scatter set.

Once you have selected the interpolation type you can choose to truncate some of the data by clicking on the Options button to launch the Interpolate dialog. Using the truncating option removes data from your raster. Some scenarios many only be visible in Plan view.

When you have selected your interpolation method, and truncation value if you so desire, then selecting OK will direct you to saving your raster file. You have two file type options:

  • Geo TIFF Tiles (*.tif)
  • Arch Info ASCII Grid Files (*.asc)

If you select the ASCII file type you may be asked to select a global projection, whereas the TIFF option does not. By default the raster will be imported into your current project.

When converting a scatter set to a raster the program may need to make some adjustments to outlying points. With each of the interpolation options, SMS adjusts the data for slightly different raster results.

You can see that the converted raster closely reflects the original dataset. The scale on the left of the Graphic Window will show you how closely the two are alike.

2D raster to scatter example

Now that you know how easy it is to convert a 2D scatter set to a raster try it in SMS today!

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Aquaveo User Conference 2019

The 2019 Aquaveo User Conference is going on now. It started yesterday, October 8th, and will wrap up today, October 9th. We are enjoying meeting with users from around the world. In attendance are users from the United States, Germany, Portugal, South Africa, and other places around the globe.

At the conference, we announced some of the new features and upcoming changes to our products that we are excited about:

  • Making XMS functionality available for use outside of the traditional interface.
  • More web-based applications for portability and ease of access.
  • Simplifying and unifying tools so it is easier to find and use the functionalities available.
  • Project management tools to track the history of a model.
  • 3D bridge modeling in SMS.
2019 Aquaveo User Conference

Talking to those in attendance, we learned they enjoyed:

  • Learning more about software features and functionality.
  • Learning how to improve their model development process.
  • Discovering benefits of Aquaveo’s software over other software.
  • Talking to developers and learning tips for model development.
  • Being able to show off their models and receive feedback on them.
Eva Loch presenting at the 2019 Aquaveo User Conference

We’d like the thank the following for participating during our user conference:

If you couldn’t make it to the Aquaveo User Conference this year, watch our website and Facebook page for future conferences.

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