Modeling Outlet Control Structures

[Anonymous]

Is there a direct approach to modeling an outlet control structure at a storage area? I’m referring to a drop box/inlet structure for which weir or orifice flow enters the box; the flow exits the box through a pipe.

I’m able to cobble together a solution, but I’m figuring there’s got to be an easier method.

[Chris G.]

I’ve found the best way to do this is:
1. Generate a rating curve that describes the head/discharge relationship for the drop inlet structure for all expected stages.
2. Add a dummy gate in an inline structure. The invert of the gate should be the same as the crest elevation of your drop inlet structure. Gate size is irrelavant.
3. For the gate type, use “User Defined Curves”.
4. Pick an arbitrary gate opening and then assign your rating curve to that gate opening.
5. In the boundary conditions editor, use T.S. Gate Openings as the boundary condition type and assign that same gate opening for the entire simulation to the dummy gate you just made.

There you go. I’ve done this many times for morning glory spillways and other drop-inlet types structures and it works like a charm.

Good luck-
Chris G.
@RASModel

[Tiff]

I saw your post and I am having similar issue. I entered the user curve for the gates and added a dummy gate at the inlet elev. I keep getting the following error.
Error running the unsteady post processor: Ryan3 unsteady
DSS File used: C:\Projects\Projects\Ryan_Dam\Ryan3unsteady.dss
Error reading data from path: /TROUT BROOK STREAM/34.5 INL STRUCT GATE #1/GATE OPENING//1HOUR/PLAN 03/
There was no data for this time window, but a record was read.
Any ideas??
Thanks
Tiffiney

[Lonnie A]

The way I’ve done this in the past is to use storage areas and connectors. I’ll connect the large storage area to a “micro” storage area that is defined as an area x depth with a very small area, say 0.01ac. This connector models the weir dropping into the outfall box. Then connect the micro area to another micro area to model the actuall outfall pipe. The downstream micro area can be tied to the outfall channel so you get the tailwater effect. Sometimes you have to increase the area of the micro basin for stability.

[Ian]

Greetings Chris,

I am modeling an inline detention area with cross sections. I am modeling the outflow control with an inline structure. I have two outflow structures. The primary, low flow, outflow structure is a circular 18″ diameter concrete pipe at the low elevation of the area. The secondary, high flow, outflow structure is a 48″X72″ drop inlet 2 feet from the top of the spillway/berm/weir. The high flow outflow structure connects through a riser to a shared conduit with the low flow outflow structure.

I have read your steps for modeling a single outlet, am I correct to assume that when I assign the rating curve to my inline structure gate, I will use a single gate with a single rating curve (reflecting the presence of both outflow structures)?

For step 5, “..assign that same gate opening for the entire simulation to the dummy gate..” Does this just mean enter the dummy gate height into the Gate Opening Height column?

Thank you for your time!

[Anonymous]

Dear Tiffy got the same error as you. do you have found the solution?.

Thanks

[Author]

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