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Solvers - General Question - SewerGEMS

Using: SewerGEMS V8i, Series 3, 08.11.03.83 1. I used to model lift stations with wet well with a short fat gravity pipe between the wet well and pump. Under the GVF-Convex solver, this is not longer the case. I am curious to know what is the reasoning behind this? 2. If using the explicit (SWMM), why does the link upstream of the pump have to be virtualized and when virtualized does this mean that headloss is ignored in these links? Thanks!
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  • In terms of why you need to do it that way with the Convex solver when you can use a conduit with the Implicit solver: please see the below solution wiki:

    communities.bentley.com/.../8986.aspx

    Regarding the virtual link - do a search for "virtual" in the included help documentation and you'll find a few sections that discuss this in detail. Basically a virtual pipe has no hydraulic significance to the network and simply passes the upstream flow to the downstream node. It's useful for situations such as submersible pumps where there is no pipe between the pump and the wetwell.

    Hope this helps,


    Regards,

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

  • Thanks Jesse and Tom -

    I did get it to work by morphing and will check the wiki, I guess I used the wrong term to search.  Thanks for pointing it to me.

    As for virtual link, I will definitely look a little closer as I don't understand that there is not a significant importance.  Discharge assemblies on pumps do have typically unions, check valves, flex tubing, 90s, etc. so before I open my mouth and put my foot in it I will do some research.  

    Thanks for the help!  

  • No problem. I created that wiki just now, in response to your post.

    If you have some piping (and headloss) between the pump and wetwell, you can choose "false" for "is virtual?" and enter the physical properties to account for headloss. If you need to use a virtual link with the Explicit Dynamic (SWMM) solver, you could account for those losses to the downstream pipe.


    Regards,

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