I have a model with a large number of control valves and pumps, and solving steady state simulations take a varying amount of trials. For instance, one scenario solved SS in ~25 trials, but after a minor-yet-significant modification to the network (added one short pipe to connect two regions within a zone) the solver requires over 2000 trials to resolve steady state. The Intra-Trial status messages indicated that the many valves were being toggled between Active/Opened/Closed repeatedly. After adding a damping limit of 0.01, per recommendation for a solver accuracy of 0.001, the solution is arrived at much more quickly (close to 25 trials). Bentley guidance typically explains damping as limiting flow changes to no more than 60% of the non-damped flow change.
Since I expect to see notable flow differences due to network modifications, is it possible that add damping would change the solution? Is it worth validating a "damped solution" with a follow-up trial that does not use damping? Any comments on the impact of damping and solutions with many control valves would be appreciated.
Note that I have updated the following wiki articles based on the information in this discussion:
Engine Compability Modes and Calculation options
Troubleshooting "Network Unbalanced" or "Cannot solve network hydraulic equations" user notification
Jesse DringoliTechnical Support Manager, OpenFlows ProductsBentley Communities Site AdministratorBentley Systems, Inc.