Dear All
I face a problem in defining the check valve downstream the pump not a built in element in the pump element, the results are not the same when defining the the check valve as a separate element.
when i define the check valve which built in the pump, the results have a dramatically change from the results i have when defining the check valve as a separate element, why this change occur.
Hello Mohammed,
Are you using WaterCAD/WaterGEMS, or HAMMER? Are the results you refer to for a transient analysis in HAMMER, or a steady state/EPS simulation?
Assuming you're referring to a transient simulation in HAMMER, the results can indeed be very sensitive to the model arrangement. With the check valve in the pump, the closure occurs inside the pump node, whereas if you use a check valve node downstream of the pump, it introduces a length of pipe between the check valve and the pump, so depending on the configuration of the pump, waves from the closed check valve can interact with the pump. It is typical for results directly next to the pump to be sensitive when closed off, as the waves will reflect and interact very quickly. Furthermore if you used a very short pipe between the pump and the check valve, it may be adjusted significantly depending on the wave speed and timestep. You can read more about that in this article:
Understanding length/wave speed adjustments and their impact on results
Also note that when using the check valve node element, you have some additional options to define the behavior of closure, which are not available with the check valve built into a pump. The pump check valve assumes instant closure whereas the check valve node can have a slow opening or closure time. You can read more about the differences between the different ways to model a check valve in HAMMER in this article:
Modeling Reference - Check Valves
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.