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2D Unsteady Flow (2024)
Objectives
This is an advanced course in applying computer program HEC-RAS. The course provides participants with the knowledge to effectively use computer program HEC-RAS to analyze difficult hydraulic conditions in natural and constructed channels, utilizing one-dimensional and two-dimensional modeling techniques.
Topics include: Developing terrain models for 2D modeling; developing Manning’s n layers; creating and modifying a 2D computational mesh; boundary conditions for 2D Flow Areas; hooking up 1D elements to 2D Flow Areas; running a combined 1D/2D model; viewing 1D/2D results with RAS Mapper; hydraulic structures inside of 2D areas; and detailed channel and floodplain modeling with 2D flow areas. Special topics for dam and levee breaching, and using 2D modeling for hydraulic structures, will also be included.
PDF material for the course Agenda, presentations, and workshops are provided below.
Instructors
Cameron Ackerman (Course Coordinator)
Stanford Gibson
Mark Jensen
Chris Nygaard
Alex Kennedy
Alex Sanchez
Eric Tichanksy
Anton Rotter-Sieren
Steve Piper (RMA Contractor)
Terms of Use
Any use or reproduction of this material must be attributed to the US Army Corps of Engineers Hydrologic Engineering Center.
Agenda
Monday
| Topic | Objective | Material | |
|---|---|---|---|
| L0 | Introductions and pre-course activities | Welcome and discussion of class expectations | |
| L1.1 | Example HEC-RAS Modeling | Overview of HEC-RAS capabilities using example applications for 2D modeling Introduction to the validation and verification of HEC-RAS. A demonstration of using HEC-RAS to create a 2D model will conclude the discussion. | |
| Break | |||
| L1.2 | Introduction to the 2D Equations | This presentation discusses the underlying 2D hydraulic equations used in HEC-RAS. Diffusion Wave and Full Shallow Water Equations in HEC-RAS will be discussed as well as scenarios where the equations are appropriate is also provided. | |
| L1.3 | Subgrid Bathymetry | Discussion on the use of sub-grid bathymetry for finite volume computations in HEC-RAS. The benefits of variable cell size on computational performance will be discussed. | |
| Lunch | |||
| L1.4 | Creating an HEC-RAS Terrain | Developing a terrain model and creating dataset for 2D modeling. Introduction to terrain download capabilities. | |
| W1.5 | Creating an HEC-RAS Terrain Workshop | Hands- on work creating an HEC-RAS Terrain dataset | |
| Break | |||
| L1.6 | Mesh Generation and Refinement | This presentation will discuss the basic concepts of creating a 2D Mesh in HEC-RAS and then how to improve and refine a 2D Mesh with Breaklines and Refinement Regions. Examples of mesh quality will be reviewed. | |
| W1.7 | Mesh Generation and Refinement Workshop | This workshop will provide hands-on experience in using HEC-RAS Mapper to create a 2D flow area mesh and refine it to capture high ground using breaklines and refinement regions |
Tuesday
| Topic | Objective | Material | |
|---|---|---|---|
| L2.1 | Boundary and Initial Conditions | The different types of boundary conditions and establishing initial conditions will be discussed. | |
L2.2 | Computational Parameters | Discussion of essential parameters and computational options for running a 2D model including equation choice, cell size considerations, and time step considerations. | |
| Break | |||
| W2.3 | Creating a Simple 2D Model Workshop | Students will create their first 2D model. Refinement of the model will be performed to understand the effect of model parameters. | |
| Review | |||
| Lunch | |||
| L2.4 | Visualization of HEC-RAS Results in HEC-RAS Mapper | An introduction to RAS Mapper is provided, specifically for visualizing HEC-RAS results. | |
| D2.5 | HEC-RAS Mapper Demonstration | ||
| Break | |||
| L2.6 | Land Classification Data | This discussion will cover creating an Land Classification dataset for use with Manning's n values in RAS Mapper. | |
| W2.7 | Land Classification Data | Student will learn how to bring land cover data into a Land Classification dataset and associated Manning's n values. | |
| Review | |||
| Kahoot! | |||
| L2.8 | Advanced Computation Options | Discussion of more advanced parameters and computational options for running a 2D model including equation choices, turbulence, and matrix solvers. | |
| L2.9 | 1D vs 2D Modeling | This presentation discusses 1D vs 2D modeling and how to choose the appropriate modeling method. |
Wednesday
| Topic | Objective | Material | |
|---|---|---|---|
| L3.1 | Combined 1D/2D Modeling | Discussion of modeling channels with 1D rivers reaches/cross sections combined with floodplains/levees using 2D Flow Areas | |
| W3.2 | Combined 1D/2D Modeling Workshop | Use a combined 1D/2D model to evaluate a protected area using 2D Flow Area and a Lateral Structure to define a levee. Levee over-topping and breaching will also be analyzed. | |
| Review | |||
Break | |||
| L3.3 | Dam and Levee Breach Modeling with 2D Flow Areas | Discussion of how to use 2D Flow Areas with 1D reaches and storage areas to perform a dam breach analysis. Discussion on using the SA/2D Connection for modeling a dam, outlets, and the dam breach. | |
| L3.4 | Determination of Dam Breach Parameters | This presentation will discuss estimating dam breach parameters for modeling dam breach scenarios. | |
| Lunch | |||
W3.5 | Dam Breach with 2D Flow Areas Workshop | Students will create an HEC-RAS model to utilize the breach functionality and evaluate parameters. | |
| Review | |||
| Break | |||
| Kahoot! | ||
L3.6 | SA/2D Connections | Discussion of how to use SA/2D Connections in a 2D Flow Area | |
| D3.7 | Terrain Modifications Demonstration | Introduction to cloning a terrain and adding a simple terrain modification. | |
| W3.8 | SA/2D Connections | In this workshop, students will utilize 2D Connections (internal hydraulic structures) inside of a 2D Flow Area to improve the river hydraulics model by overriding terrain elevations. |
Thursday
| Topic | Objective | Material | |
|---|---|---|---|
| Review | |||
| L4.1 | Troubleshooting Strategies | Discussion on common model stability issues, trouble shooting strategies, and more. | |
| Break | |||
| L4.2 | Bridge Modeling | Discussion on modeling a bridge using a 2D Connection using the 1D bridge modeling method as well as developing a detailed mesh to represent the flow constriction. | |
| W4.3 | Bridge Modeling Workshop | Students will utilize the 1D bridge modeling approach to modeling as well as develop a detailed bridge model to evaluate water surface elevations and velocities in detail. | |
| Lunch | |||
| Review | |||
| Break | |||
| Kahoot! | |||
| L4.4 | Precipitation and Wind | This presentation will discuss the use of the Precipitation and Wind boundary condition in HEC-RAS. | |
| D4.5 | DEMO Rain on Mesh | Students will walk through building a watershed scale mesh, adding precipitation data, and building an infiltration layer in RAS mapper. | |
| W4.5 | Precipitation and Wind Workshop | Students will utilize precipitation to create a rain on grid model. | |
| Review |
Friday
| Topic | Objective | Material | |
|---|---|---|---|
| L5.1 | 1D/2D Direct Connections | Learn about hooking a 1D reach directly into a 2D Flow area, as well as having a 1D reach come out of a 2D Flow Area. The concept of 1D to 2D iterations will be introduced. | |
| L5.2 | Introduction to the 3D Viewer | An introduction to RAS Mapper is provided, specifically for visualizing HEC-RAS results. | |
| D5.3 | 3D Viewer Demonstration | The 3D Viewer will be demonstrated interactively | |
| Course Closing | Post-test, course evaluations, oral critique, and closing remarks |