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thosmithIIHR

uncontrolled spillway exit

2 posts in this topic

There are two uncontrolled spillway exits in my model along with a controlled exit. How do you tell SRH2D to only let flow go over the crest when the water surface elevation exceeds the crest? Which exit condition? Exit-H, Exit-Q, or Exit-EX?

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Have you tried to represent the structure as part of the mesh? SRH-2D is very stable and I believe you should be able to add the spillway to the mesh. Once the spillway is part of the mesh (and has the proper elevation assigned), the water will only flow over the crest when the water surface elevation exceeds the crest.

The boundary conditions you inquired about are described in the manual as follows, but I would try adding the spillway to the mesh.

EXIT-H: It is a downstream exit boundary with a subcritical flow. Water surface elevation should be specified at this boundary along with the unit. For a steady state simulation, a real positive value is the input as a constant water surface elevation (therefore, elevation below zero is not allowed in SRH-2D). For an unsteady flow, a negative integer, -n, is the input. The integer, n, refers to the data function specified in the “DATA_FILE_0n” in the Global Parameter setup. If it is a time series function, time(hour) versus elevation(ft or meter) is the input data; if it is a general function, discharge(cfs or cms) versus elevation(ft or meter), the rating curve, is the data. The unit of the data is also specified: 1 for feet and cfs and 2 for meters and cms.

EXIT-Q: It is a downstream exit boundary with a known discharge where the water flows out of the domain. The input is the same as INLET-Q: discharge and unit. Caution: at least one EXIT-H is needed for modeling and EXIT-Q is intended only for cases with multiple exits. It is preferable that EXIT-H is the main exit and EXIT-Q is only a secondary exit with a small flow discharge.

EXIT-EX: It is a downstream exit boundary where the flow is supercritical. No boundary conditions are needed at such exits, neither discharge nor water surface elevation.

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