Outlet Control Structure Modelling

[RRRENG]

Hi All,

This is my first post to this forum. I had a question. I have modelled a pond with an outlet control structure consisting of a low flow orifice (Flowing to Device 1) and sharp crested weir (Also flowing to Device 1) discharging to a culvert (Modelled as the Primary).

The report states that the weir and the orifice are controlling the flows and the culvert passes XXX of XXX potential flow. We have a consultant who is reviewing this project for the Town and he is questioning whether or not the hydraulic entry head requirements of the discharge culvert are being adequately accounted for. It is my understanding that HydroCAD would account for this as when I make the outlet pipe very small, the culvert is what becomes the controlling factor.

Has anyone had this similar problem in the past? How would you respond to the consultant's concerns.

Any insight would be greatly appreciated.

Thanks.

 

[LHA]

Run a stand-alone culvert analysis for Inlet and Outlet Controls. If the large diameter pipe passes more than the orifices, call it negligible.

Engineering is the practice of the art of science - Steve

 

[psmart]

RRRENG: The report you quoted is telling you that the actual flow is less than the culvert capacity. If you examine the stage-discharge plot carefully you can often see a point of inflection where the culvert control actually kicks-in.

 

[RRRENG]

My question I guess then is, Does HYDROCAD take into account the entrance head requirements for the culvert?

 

[psmart]

The culvert is considered, in that HydroCAD evaluates each device and uses the device(s) with the most restrictive flow at each head. However, it does not specifically evaluate the water level within the riser. If you want this type of analysis, then you could model the interior of the riser as a separate "pond", however this is not normally required.

For details please see page 102 of the HydroCAD-8 Owner's Manual.

 

[TerryScan]

RRRENG,

If your question is whether Hydrocad accounts for inlet control vs. outlet control etc., I believe the answer is yes, check HELP.

 

[RRRENG]

Well,
I ended up modelling the interior of the riser as a separate "pond" using the "Catch Basin" option. I think this should be sufficient to address the consultant's concerns. It made a minor difference in the actual results, but nothing at all of note.
Thanks for the assistance.