Hello, I assume you are looking at the Help topic "Determining the Transient Run Duration" (found in the HAMMER Help documentation). If that is the case, these are general rules of thumb and may not be suited to every modeling case. For instance, if you large system and transient event, like a pump shutdown, that occurs 60 seconds after the start of the simulation, you may need to compute the model longer to see the impact. As stated in Help, you can run HAMMER "for a duration of T=4 L/a (or greater) to verify that your simulation includes the maximum and minimum transient heads (Change the duration in the Calculation Options). These normally occur within this time frame. A longer run duration may be required if air pockets form or if a gas vessel or surge tank is installed, due to the persistence of oscillations in the system. " (Emphasis added.) The Help topic then recommends trying a larger duration (T=20 L/a or greater), in order for the system approach or achieve a final steady state. Overall, this method is general and may be suited for many modeling scenarios. However, it is not try for all cases. If you have a large, dynamic system with transient events occurring. More time may be needed into order to see the transient events and for the model to reach a new equilibrium. Please let us know if you have any other questions on this. Regards, Scott Kampa Bentley Technical Support
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