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Thread: 2D Flow Limiting / 1D 2D exchanges

  1. #1

    Join Date
    May 2018
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    1

    Question 2D Flow Limiting / 1D 2D exchanges

    Sorry this post should be in wastewater section: - Admin/Innovyze could you please move this?

    Good morning.

    Whilst having a dig through blogs/ previous posts about flow limiting, i realised a lot of the information/posts were quite old. So I was wondering if there were any updates we should be aware of?
    So based on previous published information it seems that for a good 'exchanging experience'

    Good exchanging experience?
    1) Set HQ tables to have a row of data which relates to the wet/dry threshold within the 2D parameters (i.e threshold set to 1mm - HQ should have a Q for 1mm Head)
    2) Select Inflow Based on 2D linkage
    3) Use 2D elevations instead of depths for , raised MHs, or where nodes outfall into structures such as ponds
    4) Conduit invert should = 2D outfall GL
    5) Only have 1 2D node per element
    6) Ensure nodes are not sat in small elements ( flow limiting issues)

    Is there anything else that can improve stability?

    1D 2D Nodes
    I was also also hoping for a bit more information on exactly how 'Outfall 2D' works.
    How does the 1D node level effect the 2d exchange? For example if the 1D node is higher then the 2D element when does it start the exchange?

    Flow limiting?

    It is my understanding that if the flow into an element is smaller than the flow exiting that flow limiting will be implemented to ensure mass conservation.
    One way to ensure we don't have flow limiting is to ensure large elements, Would using inline banks also be acceptable practice. If the Inline bank crossed 5 elements, we would have a much greater area to ensure flow conservation.

    Any help / advice/ opinions welcome
    Kind Regards
    Last edited by BrookR; May 21, 2018 at 05:24 AM.

  2. #2
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    Moving the post to Wastewater forum per request.

    Patrick Moore

  3. #3
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    With regards the 2D Outfall, During simulation, the Outfall 2D node is treated as a series of break node, vortex control with nominal head-discharge relationship and outfall node. The nominal head-discharge relationship is defined with the following points (H,Q): (-0.001, -100), (0.0, 0), (0.001, 100). This curve is extended by the simulation engine, so it just control the flow to/from 1D/2D models in a way that prevent volume balance problems. The actual transfer of flow is again governed by the choice of the depth or elevation option.

    As a general rule of thumb I would only ever use the 2D elevations option if there was a deliberate mismatch between the node ground level and the mesh element elevation, otherwise I would use the depth option.

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