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PondPack - Trouble Modeling an Outlet Control Structure

I've been tasked with modeling this outlet control structure using PondPack. I've run into two problems:

1.) modeling the T-shaped weir near the top of the wall without double-counting the flow of the initial 1' wide weir section. Modeling the shape as an irregular weir hasn't worked, since there would be multiple elevations at the same station. I've been able to successfully model the orifice/1'wide weir combination, but the weir expanding near the top is giving me trouble.

2.) Having the flow enter and exit the composite outlet structure through separate pipes. I can't set the upstream culvert's downstream ID as the composite outlet structure.

I'm fairly new to pondpack, so hopefully I'm just missing something simple. Thanks in advance!

  • 1.) modeling the T-shaped weir near the top of the wall without double-counting the flow of the initial 1' wide weir section. Modeling the shape as an irregular weir hasn't worked, since there would be multiple elevations at the same station. I've been able to successfully model the orifice/1'wide weir combination, but the weir expanding near the top is giving me trouble.

    You should be able to use the irregular weir option to model vertical sidewalls if you set the values very close to each other, or you could use two rectangular weirs and use the on and off elevations to control which . See: Modeling a multi-stage or step weir

    2.) Having the flow enter and exit the composite outlet structure through separate pipes. I can't set the upstream culvert's downstream ID as the composite outlet structure.

    If you have outlet components in series, you would use the Downstream ID field to control this. The downstream ID would be set to the component that is downstream of it, in series. I can't quite tell from your drawing but it looks like you would have it as Culvert > Weir > Culvert. Note that culverts in series can be difficult to successfully converge and you may need to model the "bottleneck". See: Convergence problems, very slow calculations or "out of range" message when using culvert in series with another outlet component

    If you need to model storage between two separate outlet structures, you would need to use an intermediate "no volume" pond with the outlets' tailwater type set to ICPM. This enables you to use two separate Composite Outlet Structures. This is mentioned in places such as this article. This might be what you need to do if you have the culvert discharge to both a weir and orifice which then discharges to another culvert. If you can assume that the culverts have more capacity than the weir/orifice, you could omit the culverts and have one outlet structure with the orifice and weir set to "tailwater". If the culverts need to be modeled, then the first outlet structure would be the upstream culvert, discharging to a pond with volume type set to "no volume", which then has another outlet structure with the weir and orifice "downstream ID" set to the second culvert.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Adam Bendrick