Ever since I have updated my SewerGEMS software to the Connect Edition Update 3, I have been experiencing irregularities with how a Pond Element would drain. I have ponds set up with an elevation-volume table and then I set the "Elevation (intial)" and I run the scenarios to see how the ponds would drain through a series of pipes. This has always been working fine, but since the update, the pond water surface elevation starts a lot lower than what the initial elevation is set at. Also, the flow continuity error is about 80% when it used to be about 0%. Is there a change to the software that could be the reason why I am no longer seeing the same results anymore?
Thank you,
Ryan
Hello Ryan,
We haven't heard this before, had you designed the pond before updating to SewerGEMS CE update 3 or you designed the pond after updating? I checked in the sample model, I couldn't reproduce such issue.
Are there other user notifications in the model about flooding in the model or pipes with zero flow which would increase the continuity error? There also could be data entry issues, please go through below wiki for more details.
Troubleshooting unstable SewerGEMS and CivilStorm results using the implicit solver
If possible please upload model files for our review.
Sharing model files.
Regards,
Sushma Choure
Bentley Technical Suppport
Hello, i am the design lead on the project Ryan Haller is working on, he started the posts here requesting some assistance. The primary question that has not been answered is that the starting WSEL is erroneous in the model. This is a high priority since we cannot go back to an earlier version. Please help us with that as soon as you can.
Hello Robert,
We are looking into the updated model sent by Ryan, will reply back soon.
Hi Robert and Ryan,
The problem with the initial water surface of the ponds appears to be related to the "Use Bentley Transition Equation" calculation option. The default is "false" and you have set it to "True". For some reason, enabling this option causes problems with results in this model. If you change the option to the default "false", the water surface elevation will begin at the expected value. We will look into why this happens in case there is a future improvement to be made with the solver but for now I have added a note in this article.
To help achieve stable results, I also made the following changes:
I also noticed that your pond outlet structure are set to not use a control structure - while the solver will use the downstream conduit geometry for outflow control in this case, using a control structure in the pond outlet node tends to yield more stable results. I did not attempt to try this since I do not know if the control structure should match the shape of the conduit, but it is something you can look into for further stability improvement. I see that the first conduit after the ponds is 7' X 7' but a much smaller pipe just after it, which may be leading to convergence problems.
If further assistance is needed, I will also take a look at the option of using the Implicit solver.
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Ryan Haller
Thank you! When I was using Connect Edition Update 2 I had a flow continuity error of about 2%. I never changed the calculation settings and suddenly was seeing an error of 82% after getting the Update 3. I'm glad I'm starting to see accurate results again.
Hi Ryan, glad to hear it. The new version does use the newer SWMM solver version (as seen here) so it might be related to that, but I've reported this to our developers in case there is a problem with that particular calculation option. (reference # 382665)