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Multistage

3 REPLIES 3
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Message 1 of 4
Anonymous
1385 Views, 3 Replies

Multistage

Can multistage structure be used for model tailwater backflow at outlet
control box ?
3 REPLIES 3
Message 2 of 4
annw2
in reply to: Anonymous

I'm not sure I understand the question, but you can model varying tailwater through interconnected ponds.
Ann Wingert, P.E.
Message 3 of 4
Anonymous
in reply to: Anonymous

Yes. The MultiStage option in Hydraflow Hydrographs places
Culvert/Orifice A as the downstream receiving end of those structures
that contribute.

For example, if you have a 24 inch pipe outlet to your Pond Riser (which
defaults to multistage- think a big L) that also has a 4 inch hole 2
feet below the Riser Top. The pond emergency overflow bypasses the 24
inch pipe.

Culvert A receives the flow from Orifice B, and Weir A. Weir B would be
not assigned as multistage.

Hydraflow Hydrographs will calculate Culvert A and determine the
headwater elevation associated with various flow values. That headwater
then becomes the tailwater for Orifice B and Weir A. Hydraflow will
calculate the reduced flow values based on the submerged outlets. See
the help documentation for the calculations associated with this.

Matthew Anderson, PE



EK wrote:
> Can multistage structure be used for model tailwater backflow at outlet
> control box ?
>
Message 4 of 4
gonygonygo
in reply to: Anonymous

Matthew, when you say "calculate culvert A", do you mean it calculates the HW for the combined flow it receives?  I have been pulling my hair out over this for a few days now.  I have a similar scenario where I am dealing with submerged weirs flowing into a "user" outlet pipe since hydraflow won't model my arch culverts.  I cranked them out by hand/spreadsheet and determined their stage-discharge relationship. 

 

So, for a given stage upstream of the multi-stage weir structures, "the HW produced by culvert A" (downstream of weir structures) will be the total flow rate from both contributing structures (Qr each) matched to the controlling HW depth for culvert A plugged into their Qs equation??

 

This doesn't seemed to be explained clearly in the user manual (or I am slow).  I actually posted about this same issue recently. 

 

Also, it would be nice for Hydraflow Express to allow modeling of combination weirs of the rectangle/v-notch variety.

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