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network is not capturing the full flow from the catchments

Hi,

I have an issue with my Hydraulic Model.

I have analysed my model with two different approaches.

  1. For Catchbasins I used Full Capture type in Inlet option. Dimensions are 0.6mX0.6m.

              Used user-defined gutter-> Conventional-> Max Gutter depth 0

 

  1. Defined a catch basin with same dimensions in Inlet catalog and used it. Also defined gutter in catalog.

            Used max gutter depth 0.06 m in this case(global edit in Catchbasin FlexTables)

Now the issue is, in second case it looks like the network is not capturing the full flow from the catchments. I checked the total flow from catchment contributing to a pipe and checked the flow in the pipe, they are not matching. In case 1 its matching.

I want to know if I had done a mistake. Please help me through this.

Case 1 Images:

Case 2 Images:

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  • Hi Kartheek,

    I have taken a look at the model files and I see that in both cases all of the flow is captured, but the ponded area that you have chosen to add above the rim is causing the inlet inflow to be attenuated in the case where the inlet type is set to Catalog Inlet. You can see this by graphing "Flow (total in)" along with "Flow (total out)" for the catchbasin.

    I believe the reason why this does not happen when the inlet type is set to full capture is because in this case, the gutter is not considered, so the ponded area above the gutter does not come into play, and thus the catchment runoff enters directly into the catchbasin. (if overflow later occurs, the ponded area would be considered).

    In the case where the inlet type is set to catalog inlet, gutter hydraulics are enabled, and the program considers the impact of the ponded area. Catchment runoff first enters the ponded area and then becomes attenuated as it enters the inlet, similar to pond hydraulics with outlet structures. I am discussing this internally with our developers to confirm that this is indeed expected behavior. In the meantime, please confirm if you intended to have a large ponded area above the inlet.


    Regards,

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

  • Hi Jesse,

    I have changed the Ponded area at inlets to lower value(50m2) and the flow values are almost matching. But two new issues raised.

    1. There is huge overflow loss in 10-Year Scenario and

    2. The Hydraulic Profile is looking bad in few places of network. I have attached one image for your reference. Check the maximum HGL of first inlet.

      

    I am unable to understand where it went wrong. Please help me through this.

    Thanks,

    Kartheek

  • Hello Kartheek,

    This is the overflow from the catch basins. Due to less storage area (50 sqm) now, there is overflow at the catch-basins which is causing the high HGL values. Try to use the gutter element in parallel to your catch-basins to capture the overflow.

    Basically what is happening is that once the storage area for your "In Sag" inlets is getting filled up; its overtopping with overflow and hence the high HGL values.


    Regards,

    Yashodhan Joshi

  • Hi Yashodhan,

    When increasing the storage area/Ponded area to higher value(say 500 m2) the overflow is decreasing but the inlets are not capturing the all the flow from catchment. This is the query actually I posted in this thread. Previously the Ponded area is around 1500m2. Upon   suggestion, I have reduced the ponded area to 50m2 and the Max HGL is increasing. You suggested to use gutter element. I have already defined gutter. Do you want me to draw the gutter in the entire network?

    Thanks,

    Kartheek

  • Kartheek,

    Are you using catalog inlets in this case? Can you provide an updated copy of the model? I've done some testing in a small example model and I'm currently discussing with our developers the general topic of how the ponded area option is handled in various situations with the SWMM solver.

    Generally speaking models with excessive surcharging/overflow tend to be challenging for the numerical solver, requiring additional finesse to achieve stable results. I'd like to get a clear understanding of your current specific situation to make sure we can focus on that use case. If you're able to set up a small cut-down version of the model that demonstrates the issue, that would be ideal.


    Regards,

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