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Submerged outfall

Hi, 

In my model I have an outfall from storm sewer directly to a nearby river. It works smooth when the boundary conditions are set so that user defined tailwater is set below the top of the sewer/outfall (even 1 cm is enough). When I change the tailwater to be equal or above the top of the sewer/outfall I get constant information: The model did not converge ... regardless if the chosen calculation options.. 

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  • Hello,

    I responded to a service request you also created, but I will post the response here as well so other users may possibly benefit from the solution. 

    First, I would recommend starting with the default calculation options. Some of the values in the model you provided in the service request, like the LPI coefficient, were much different that the default and could contribute to some instabilities. The simplest way to get to the default values is to create a new calculation option and assign that to the scenario you are using.

    Once you do that, change the Output Increment and Calculation Time Step to 0.01 hours. Also set the NR Weighting Coefficient to 0.98 and the NR Iterations to 40. With this setup, I was able to compute the model without the convergence error.

    This link includes these troubleshooting steps, as well as some other: Troubleshooting unstable SewerGEMS and CIvilStorm results using the Implicit solver.

    Regards,

    Scott

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  • Hello,

    I responded to a service request you also created, but I will post the response here as well so other users may possibly benefit from the solution. 

    First, I would recommend starting with the default calculation options. Some of the values in the model you provided in the service request, like the LPI coefficient, were much different that the default and could contribute to some instabilities. The simplest way to get to the default values is to create a new calculation option and assign that to the scenario you are using.

    Once you do that, change the Output Increment and Calculation Time Step to 0.01 hours. Also set the NR Weighting Coefficient to 0.98 and the NR Iterations to 40. With this setup, I was able to compute the model without the convergence error.

    This link includes these troubleshooting steps, as well as some other: Troubleshooting unstable SewerGEMS and CIvilStorm results using the Implicit solver.

    Regards,

    Scott

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