If you look at the "Storage Area Connection Weir Data", there is a field for input of "Standard Weir Equation parameters". I typically like to take the cross sections right to the peak of the high ground feature, but start my 2D cells at the toe of the feature. Do not have cells adjacent to the lateral structure that reside completely on the slope of the levee/berm/whatever you're modeling with the lateral structure. Be careful not to use too high of a weir coefficient. As far as advice to reduce 1D/2D flow errors over lateral structures: Break up long lateral structures into multiple smaller ones. It is purely there for graphical purposes. Also, keep in mind that the weir width is not used at all in the computations (weir or 2D equations). This might just be another good example where you try them both as part of your sensitivity analysis. HEC does caution against using the 2D equations if the connection is elevated such that water going over it will experience "free fall" (i.e. If it is overland flow, I'd lean towards using the 2D equations. So for me, if it's an elevation connection, I'd lean towards the weir.
#Geo 5 fem embankment over concrete box culverts full#
Although the 2D equations come with their own subjective assumptions and limitations: terrain quality, theta value, eddy viscosity, full momentum or diffusion wave, etc, etc. The weir equation requires a very subjective weir coefficient. I like to think about the input data required and how confident I am with it. Toby-Great questions! the quick answer is: "if it is acting like a weir, model it as a weir, otherwise model it with the 2D equations." However, as with many things in RAS, there's a lot more nuance involved.
Use Weir Equation)? If one is trying to model a 1d/2d connection where there is overland flow and a non-elevated overbank, what might be the benefits or shortcomings of each method? What would you set your weir width to for an overland flow situation with a low weir coefficient chosen from the table above? Any other advice to reduce 1d/2d flow errors over lateral structures? Please clarify.ĭo you have any insight into the new "Overflow Computational Method" for lateral structures into a 2d area (e.g. I don't know what the "with" parameter is. In a ogee crest spilway what is the meaning of the with parameter? The downstream section of the weir is the natural stream section or its located at the end of the ogee profile? I have a question about modelling gated weirs with ogee shape. Hi Chris……….My name is Rodrigo and i am from Chile. However, to the extent you can simulate the effect of a stepped spillway on the upstream energy head using the equations above, it can certainly be part of a HEC-RAS model.
HEC-RAS is not a suitable tool to simulate detailed hydraulics down a stepped spillway. Can a stepped spillway simulation performed with HEC-RAS?
0 kommentar(er)
