My scenario is not converging on a solution when once computed. I am getting a message in the calculation summary that "Convergence is NOT achieved."
The calculation solver was not able to converge on a solution given the number of traversals of the network and/or other unresolved user notifications
In the user notifications dialog box you can double click on each notification and if it relates to a single element you will be brought directly to that element in the drawing pane. If there are many of the same type, right click on one of the user notifications and choose "select all elements with message id...."
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Contact Technical Support for patches. See:Cumulative patch set frequently asked questions
Pipes that are very short can tend to cause problems like this. Either correct the length, combine multiple pipes in series, or manually enter longer lengths. This can be done for example by filtering the conduit and/or channel flextable on Length (Unified) less than 5 ft, the global edit "Has User Defined Length?" to True, then global edit the user defined length field to 5 ft.
Open the calculation options for the current scenario (Analysis > Calculation Options)
Try increasing the number of network traversals. Start with a large number like 50. If that doesn't work try 100. If that doesn't work then there may be data entry issues or something else wrong with the model. If careful review does not surface the root cause, contact technical support or post on the Hydraulics and Hydrology forum. If 100 does work then increase the number until you find the lowest number that still allows the model to converge.
If the non-convergence is associated with a pressure subnetwork, click the "Pressure Summary" tab of the Calculation Summary and review the related subnetwork . You may notice a specific timestep(s) that are not converged (as indicated by a "False" in the "Balanced?" column). Click the timestep in question and click the "status messages" tab at the bottom for potential clues. Next, use the Time Browser to locate the timestep in question and review what is happening in the model at that time. Here are a few possible reasons why the model may struggle to converge:
See more in the following article (note that most are related to WaterCAD/WaterGEMS but some information applies to SewerCAD/GVF-Convex Solver): Troubleshooting the Network Unbalanced
In the calculation options, try setting "Use Explicit Depth and Slope Equations" to "True". This can help with circular pipes that have trouble converging. For more details on what this does, please see the Help.
Check the model for complex diversion situations ("Is Diversion Link?" = "True"). For example multiple diversions in series. Reduce complexity and excessive diversions wherever possible.
If you're experiencing Non-convergence and your model is severely undersized, with significant flooding occurring, please note that this can often be the cause of non-convergence. This condition makes it more difficult for the solver to converge. More recent versions of the product handle this situation a bit better when increasing the max trials option mentioned above, but it is worth considering the limitations regarding flooding with the GVF-Rational numerical solver. The HGL will be reset to the rim elevation and the flow will continue in the pipe, whereas in the real system some of the flow will be lost. See the article below for more on this.
Different results when changing Maximum Network Traversals
Understanding how Maximum Traversals help with non converging models
Why is the HGL reset to rim elevation for flooded structures?
StormCAD hangs when trying to compute, reporting that it is Not Responding
Troubleshooting the Network Unbalanced