Some also distribute the software in countries that are not permitted to access US Army web sites. Various private companies are registered as official "vendors" and offer consulting services and add-on software. It is in the public domain and peer-reviewed, and available to download free of charge from HEC's web site. HEC-RAS has merits, notably its support by the US Army Corps of Engineers, the future enhancements in progress, and its acceptance by many government agencies and private firms. It can be used for dam breach analysis, though other modeling methods are presently more widely accepted for this purpose. Some of the additional uses are: bridge and culvert design and analysis, levee studies, and channel modification studies. HEC-RAS finds particular commercial application in floodplain management and studies to evaluate floodway encroachments. HEC-RAS is a computer program for modeling water flowing through systems of open channels and computing water surface profiles. Version 5.0.7 as of March 2019 supports Windows 7, 8, 8.1, and 10 64-bit only. It is capable of modeling subcritical, supercritical, and mixed flow regime flow along with the effects of bridges, culverts, weirs, and structures. Certain simplifications must be made in order to model some complex flow situations using the HEC-RAS one-dimensional approach. HEC-RAS is equipped to model a network of channels, a dendritic system or a single river reach. The unsteady flow equation solver was adapted from Dr. These situations include hydraulic jumps, hydraulics of bridges, and evaluating profiles at river confluences.įor unsteady flow, HEC-RAS solves the full, dynamic, 1-D Saint Venant Equation using an implicit, finite difference method. The momentum equation may be used in situations where the water surface profile is rapidly varied. Energy losses are evaluated by friction and contraction / expansion. The basic computational procedure of HEC-RAS for steady flow is based on the solution of the one-dimensional energy equation. It includes numerous data entry capabilities, hydraulic analysis components, data storage and management capabilities, and graphing and reporting capabilities. The Hydrologic Engineering Center (HEC) in Davis, California, developed the River Analysis System (RAS) to aid hydraulic engineers in channel flow analysis and floodplain determination. The program was developed by the United States Army Corps of Engineers in order to manage the rivers, harbors, and other public works under their jurisdiction it has found wide acceptance by many others since its public release in 1995. The release of Version 5.0 introduced two-dimensional modeling of flow as well as sediment transfer modeling capabilities. Prior to the 2016 update to Version 5.0, the program was one-dimensional, meaning that there is no direct modeling of the hydraulic effect of cross section shape changes, bends, and other two- and three-dimensional aspects of flow. But if your lateral structure does not represent an elevated terrainįeature (e.g.HEC-RAS is a computer program that models the hydraulics of water flow through natural rivers and other channels. New feature available in lateral structures. Just use the 2D equations over the lateral structure instead of the weirĭomain” (this is just a funny way of saying “Use 2D Equations”) is a relatively However, in this case, it might be better to Low weir coefficient on the order of 0.1 to 0.5, as discussed in the 2D Modeling User's Manual on page 3-50. it is not a levee), you would want to use a very If there is no elevated feature representedīy the lateral structure (e.g. Transfers from the river to the cell for a given timestep. This will reduce the volume of water that You might also reduce the weir coefficient. Read more about the weir submergence decay exponent in the HEC-RAS User's Manual on page 8-41. This has a dampening effect on the oscillationsĪnd errors you get from this situation. Value of 1 to 3 (1 is the most accurate, 3 is the most stable). Structure, you could change your weir submergence decay exponent from the default Now if you’re using the weir equation on the lateral
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