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Thread: Connecting to a Pressurized FM - InfoSWMM

  1. #1

    Join Date
    Aug 2017
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    Connecting to a Pressurized FM - InfoSWMM

    I have a model that outfalls into another pressurized system. I am wondering what is the best way to simulate this.

    I tried creating a free outfall with invert elevation of 20ft. However, the outfall registered 0 flow.

    Should I try using a control structure with an outlet set at elevation 20ft and the (free) outfall at 0

    Also, how do I make sure that all of the pipes in my system are full of water/wastewater before the simulation?

  2. #2
    Forum Moderator

    Innovyze Employee



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    Edwardo,

    I am going to move this discussion to the WasteWater forum as it appears this is an InfoSWMM question and those are best addressed in that forum. The "Water" forum is primarily for pressurized water flow using software such as InfoWater or InfoWorks WS where all pipes always flow 100% full while the WasteWater forum is for Gravity flow and forcemain analysis using software like InfoSWMM, InfoSewer, InfoWorks ICM where pipes may or may not be flowing 100% full. There are different equations governing both software, that it is always best to ask your question in the forum that is most appropriate for that software.

    Patrick Moore

    Can someone help Edwardo with his question?

    If you don't get a response quickly enough please email us at support@innovyze.com and someone on our support team can assist you.

  3. #3
    Senior Member
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    Feb 2013
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    In ICM, applying a constant level of 20ft above the level of the outfall to the outfall node would do that. I imagine InfoSWMM is similar. That should take care of the initialisation issue too.

  4. #4

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    Aug 2017
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    I am still trying to solve this problem.

    I believe I have identified the issue. For some reason the water within my dummy nodes JCT-1160 and JCT-1246 is not rising above top elevation of all the other nodes in the system.

    Allow me to explain from the very beginning

    I need to model a city-wide sanitary sewer forcemain system that ultimately discharges into a pressurized system (neighboring city).

    The way I have the model set up is:

    Wet-well -> Lead pump/Lag pump -> Junction Node -> pipe network -> Dummy node A -> Weir -> Dummy Node B -> free outfall.

    All of the nodes have a surcharge depth of 100,000ft and a ponded area of 1-ac.
    The weir between the two dummy nodes has a height of 46-ft to simulate a connecting pressure of 20psi.

    What I would expect to happen is that none of the junction will exhibit flooding and that the water within Dummy Node A will rise up to the weir elevations and ultimately discharge into the free outfall.

    Instead what is happening is that water is actually staging up and ponding on my junctions, overcoming the 100,000-ft surcharge depth.


    Capture.PNG


    I have tried lowering the weir height to 0, and the model does behave as expected and with a very little continuity error to boot.

    This leads me to believe two things:

    Either A, I should not be using weirs as a means to model the connecting pressure.

    or B, for some reason the surcharge depth is not being accounted for in the model.

  5. #5
    Senior Member
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    Feb 2013
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    You should not be using weirs. I don't now InfoSWMM, I'm an ICM user, but I expect they have similar functionality. In ICM, I would use the "force main" model for the pipework. But is it even necessary to do all this? Is the pump discharge affected by pressure downstream? If it is a constant pump rate under all conditions, then you may not need to explicitly model the rising main (force main).

  6. #6

    Join Date
    Aug 2017
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    Well, I input into the model the on/off conditions and the pump curve. I expect the pump to behave differently under different head conditions.

  7. #7
    Senior Member
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    Feb 2013
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    I hope an InfoSWMM user can be more help.

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