Understand the troubleshooting options available in ICM.
In ICM, there are several tools to help with troubleshooting and fixing simulation issues, whether they are poor performance, erroneous results, or simulations that fail to complete.
Once a simulation is run, the color-coded icon displayed next to the simulation in the database indicates its status:
The most powerful tool for troubleshooting a model is the diagnostic timestep log:
The timestep log details each timestep halving and the location of the last non-convergence related to the 1D engine. For a 2D model, the 2D timestep and location of the minimum timestep is also output.
When trying to troubleshoot RTC, enable those additional options to investigate why it is not operating as expected. If the RTC is large or complex, consider troubleshooting RTC in a smaller cutdown model.
The log report provides a summary of the failure and unconverged locations once the simulation is complete:
Possible issues may relate to erroneous data or inappropriate headlosses being applied.
While simulation failure may be a result of the 1D engine, the problem may stem from the connection with the 2D domain. Inside the log report, inspect general 2D volume balance for any large discrepancies between total inflow and total outflow plus storage. This indicates that the connection between engines is producing considerable volumes of flow and should be investigated.
When 1D and 2D elements are connected at nodes, an engine check looks at the volume in the element and makes corrections using flow limiting:
The initialization phase is important for a river model. Due to the scale of rivers over pipes, steady state thresholds can sometimes be too large for a river model, and the simulation initializes prematurely. Inspect the duration of the initialization in the log results report or check the model outflow at the start of the simulation. In the example below, the model took just over 3 hours to initialize, which was not sufficient to fill the river reaches. The river reach was still filling during a period of the simulation, rendering the simulations inaccurate.
To overcome potential initialization issues, the initial conditions object could be used to backfill sections of river reach. The hydrology may need to be primed so that the starting inflows are higher, resulting in a more appropriate initialization final state. Another option is to manually generate the intended steady state via a separate simulation, and then use this simulation instead of undergoing the initialization process.
There are also some simulation shortcuts for non-convergence. The issue may be an inappropriate simulation timestep. Shown below are some guidance timestep values:
Other issues may be related to steep pipes in combination with high headlosses, which can cause inappropriate calculations.
For more hints and tips, check out this blog post: Troubleshooting hydraulic models in InfoWorks ICM.
