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Relationship between System CA, System Intensity and Flow (Total Out)

Hello,

I have a plot which is divided into sub areas, 10 to be specific, with individual outfalls. All outfalls are "Free Outfall". Each sub area is a gravity drained system served by catch basins and underground piping connecting to the respective outfall. All catch basins are subject to same rainfall intensity, ie. same time of concentration and same runoff coefficient. I am running this in GVF environment. 

after running the model i noticed that in some, 5 to be precise, of the outfalls, the product of "System CA" and "System Intensity" matches "Flow (Total Out)" but in other cases it does not. It can vary almost by 100%. 

I looked at a previous forum answer on flow balance at junctions in GVF, which does not seem to explain this situation because why would some outfalls, the product would match and not on the others. Secondly, the Tc at the outfall and the individual catchment areas is within a few percentage point, so intuitively the discharge rates should be similar. 

what could explain this difference?

thanks

KP

Parents Reply
  • Thanks for sending the model. This was a known issue in the older version that you're using (10.00.00.45). It was first reported in 2016 in this thread, and fixed in 2018. The latest available version (10.02.02.04) does not have this problem, and the Flow (Total Out) for outfalls with multiple incoming pipes is reported correctly (for example 3.03 CFS for outfall O-LS4 in your model.)

    Please see the following article from our Wiki for information on upgrading: Downloading OpenFlows Software


    Regards,

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

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