This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Subcritical and Supercritical flow in SewerGEMS

Good morning,

I simulated a sewer system in SewerGEMS with the calculation options Covex, Dynamic wave and SWMM Solvers. In the simulation with the Dynamic Wave option, it notifies me that I have a froude number greater than 1, what does that mean?
Another doubt that I have is that with the Dynamic Wave option the flow rate through the outfall is 18.27 l / s but in the Convex and SWMM Solvers options the flow that comes out is 18 l / s. Why this difference in flow? .I attach the model in SewerGEMS to be reviewed.

Sewer system.stswpkg.zip

Parents Reply Children
  • Hello Alexander,

    The depth/rise varies from solver to solver.

    For Implicit Solver - depth/rise is active depth in the middle of the conduit or channel by rise.

    For GVF-Convex and GVF-Rational Solver - depth/rise is the average depth in the link by rise.

    For Explicit (SWMM) Solver - depth/rise is depth calculated by Explicit engine by rise.

    You can find the differences in the different solvers and how they operate from the links provided in the earlier response,

    Hope this helps.


    Regards,

    Yashodhan Joshi

    Answer Verified By: Alexander Benites  

  • Hello Alexander, 

    You are right pipes aren't working under pressure in your case.

    The notification about "A supercritical to subcritical transition is occuring during this time-step" means that a hydraulic jump may be occuring, which you might want to be aware of.

    And notification about "One or more elements had a Froude number greater than 1 during this time-step." means that supercritical flow occurs in the pipe at some point, which you might want to be aware of.

    It is basically implying this transition in conduit CO-10(2), in your case, as seen in the below screenshot. 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

    Answer Verified By: Alexander Benites