Courant Stability Criterion

Hello,

I am currently working on the construction and modeling of sewer networks using SewerGems software version 10.03.04.53.

As a requirement of the client I have been asked to verify that the results obtained in the modeling comply with the Courant condition.
Reviewing the calculation options of the software, I found the option "Use Variable Time Step? and "Time Step Multiplier" which as indicated in the description of each of them serve to ensure that the Courant condition is preserved.

According to the above I understand that the model during the run performs Courant checks and time step variations to fulfill this condition, I do not find within the model results of these Courant checks or the Courant value for which it is considered that this condition is being fulfilled.

I have also searched in the help documentation or the help center for the calculation bases or formulation used by the model for the Courant verification, but the only thing I can find is the description of the parameters mentioned above "Use Variable Time Step? and "Time Step Multiplier".

I would like to know how I could verify inside the software or in the software documentation that, once the modeling of the networks is finished, the Courant condition is being fulfilled.
 
I need help with this.

Thanks in advance.
 
  • Hello Juan,

    I have discussed this with my colleagues and so far my understanding is that when you use the Explicit (SWMM) solver in SewerGEMS (or CivilStorm), the Courant condition is automatically fulfilled when using the "Variable Time Step" and "Time Step for Conduit Lengthening" calculation options.

    Typically with dynamic modeling you will be most interested in achieving stable model results with low mass balance error and low percent non-convergence. These are shown in the Calculation Summary. If you find that these are too high, you can use the guidance in the following article: Troubleshooting unstable SewerGEMS and CivilStorm model results using the Explicit SWMM Solver

    If you still need statistics about Courant criteria/adherence, you can consider submitting an Idea to our Idea Portal. However as far as I can tell, EPA-SWMM itself does not appear to report this.

    I will let you know if I receive any further feedback from my colleagues. Note that you can also find some discussions on this topic in the openswmm.org forum.


    Regards,

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

    Answer Verified By: Juan David Garcia Jiménez