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Curb Inlet on Grade Efficiency

I checked SewerGEMS help and found Bentley SWMM is using HEC-22 equation to calculate the inlet efficiency, is that correct?

upon reviewing the efficiency calculated by the model for example (CB-433) in the shared model with scenario "5 Year 45 minutes" and perform the hand calculation as in the shared excel sheet; I would clarify the followings;

1- does SewerGEMS calculate the inlet efficiency as per HEC-22 shown in the help?

2- why the hand calculation does not match with the model results as shown in the shared excel? can you provide an excel modified in case there is a mistake in my excel for verification?

3- would you please elaborate why the graph in the efficiency does not back to 100%, it ended to the end of simulation at 40% ? while the excel shows the graph back to 100?

PS: in the same shared model; when I do zoom extend the model does not extend and I zoom little out I saw many dash lines, I did compact Database and Update Database Cache but still the problem there (Screenshot is below).

The model and the excel are shared in Bentley Share Drive

Regards,

Mohamad Azzam

Parents
  • Hello Mohamad,

    This appears to be related to a similar issue that you reported earlier. It looks like modeling noise is having an impact on the capture efficiency. I will make sure the development team are aware that this issue is continuing. 

    Regards,

    Scott

  • Dear Scott

    That modeling noise belongs to point 3, in that post was to InSag, but this is On Grade. we need to present the graphs to the client. any workaround/advice or patch.

    what about the other points? the HEC-22 and the calculation comparison between the excel and the model.

    Also the display (Zoom extend issue).

    Kindly advise.

    Thank you,

    Mohamad

  • Mohamad,

    You appear to be using the flow from the upstream gutter, but that is the flow on the start (upstream) side of the gutter, and there are also attached catchments which contribute to the flow that approaches the inlet. If I look at the "Flow (Local Surface)" result in the catchbasin properties and use that for your hand calculations, the results should match what SewerGEMS shows for the capture efficiency.


    Regards,

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

  • Hello Jesse,

    Thank you - I used the gutter flow because the formula " Q is gutter flow".

    I followed your advice and the graph by using the "Flow (Local Surface)" is matching, except that the graph from the model stay fixed at 40%, would you please elaborate the behavior of the graph? why the graph does not back to 100% since all flow discharged to the outfall?

    Regards,

    Mohamad

  • As discussed earlier, once the flow gets too low, the efficiency cannot be calculated properly and you will need to ignore the capture efficiency at such low flows. Our developers will look into fixing this in a future release. See: Unexpected capture efficiency at zero flow or during gutter reverse flow conditions


    Regards,

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

    Answer Verified By: Mohamad Azzam 

  • Dear Jesse,

    Thank you for your feedback, I did go back to previous posts as well and all that help. for other clarification needed in Ponded Area I will post separately.

    For efficiency issue, in case next release is taking time, is providing a patch for the current release possible? if that possible will be great and will help us to update our report's graphs which we are receiving comment and need to be covered with our clients.

    Your support is highly appreciated.

    Mohamad. 

  • A patch is not available at this time as the developers have not yet worked on it. It is planned to be addressed in a future update.


    Regards,

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

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