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SewerGems Hydraulic grade line in profile is not correct, also drastic change in HGL peak level along same segment.

Hi All,

I am using SewerGems (connect edition), I believe most users of the software might have encountered this issue.

While working and checking the network profiles it is observed that, HGL (water level) shows drastic level change. In principle water level shall be stable and constant at all manholes if there is no forward flow (theoretical).

Settings are - Stormwater drainage model analysis of existing network designed in EPA SWIM (InfoSWIM). Explicit (SWMM) is selected in calculation option. Time step 0.5 sec, run for 24 hr, rainfall - Time depth curve for SCS Type II.

It is strange behaviour, does anyone have solution?

Personally I tried to play with time step (considering instability) even though there is no change.

Another try was reduce the number of nodes and run, still the behaviour of HGL not improved.

Moreover, the EGL always shows random levels and not correct - any idea why this is appearing like this. In any case the EGL for gravity pipe shall not rise above ground (partially full pipe).

I have constructed several models in SewerGems and unfortunately the results are not acceptable for any design validations. Please reply if any solution exist.

  • Hello Mukesh,

    You are using an older version. It is possible that updating will help with the issue, since we are always improving the results.

    Reviewing the results in Hydraulic Reviewer might also help reveal issues at individual nodes. The continuity error might not show areas of concern at specific nodes. The Hydraulic Reviewer will show the deviation between the inflow and outflow volumes, and may indicate issues in the model.

    Regarding the error message, we would need the details of the error message. You can click the "Click here to see the details" button in the lower left of the dialog you provided above. 

    We don't have a service center in UAE. We hold to confidentiality and will not share the model under any circumstances.

    Regards,

    Scott

  • Hi Scott Kampa,

    Thank you very much for the immediate reply.

    I am using SewerGems Connect edition 10.00.00.40. but the version shouldn't affect the HGL behaviour.

    Well there is no branch coming up however some backwater effect is there but still small red mark for HGL max seen up and down ( not stable ).

    The flow continuity error is -0.3 and Runoff continuity error is - 0. I will try the troubleshooting from the provided link. Implicit solver takes too much time to run same setting. The results shows huge flooding at downstream (HGL is 2.2m above GL)  got below error while opening profile.

    It is required to validate existing model with SWMM,  and therefore idea of adapting implicit calculation method not practical.

    The model is confidential data from our client and cannot be shared without proper approval (and not possible to get approval at this time) . I would like to know do you have any service centre in UAE so I can personally meet and discuss this issues.

    Appreciate the response.

    Mukesh

    Mukesh Vhirodkar

    Utilities Designer

    WS Atkins, Abu Dhabi, UAE

  • Hello Mukesh,

    First, if you are not using the latest version of SewerGEMS, I would suggest upgrading to that. The latest version is SewerGEMS CONNECT Edition Update 1, build 10.01.01.04. 

    Is there some additional inflow, such as from another branch, which might account for the increase in HGL on the downstream end? It appears that the maximum hydraulic grade at around 1450 meters increases substantially there.

    Also, what kind of continuity error are you seeing? If this is high, further adjustments may be needed to improve the results. This link has more information on troubleshooting issues with the Explicit solver.

    Finally, have you tried using the Implicit solver to see if the results are better? 

    If this doesn't help, we will likely need to see a copy of the model files. To send these, please following the steps in this link: Sharing Hydraulic Models on the OpenFlows forum.

    Regards,

    Scott

    Answer Verified By: Mukesh vhirodkar