How do I model a positive displacement pumps (screw pump, lobe pump, sliding vane pump, etc...) in HAMMER?
HAMMER cannot accurately model a positive displacement pump using the pump element. Positive displacement pump characteristics are completely different from those used for four-quadrant pump curves used in HAMMER.
However, it is possible to approximate a positive displacement pump.The best way to model a positive displacement pump would be to use a Periodic Head-Flow element.
First, you would need to externally calculate the flows out of the pump over time and compile a table of flow versus time. Then you would use two "periodic head-flow" elements in the model, one representing the suction side and one for the discharge side, with a gap between, as shown below.
In the Properties display for the Periodic Head-Flow elements, you would set the attribute "Transient Parameter" to Flow. For "Sinusoidal?", choose False.
This will allow you to define the Flow Pattern table for flow versus time. The tables for each will need to be identical, except that the values for flow. On the suction side, the flow values will be positive. On the discharge side, they will be negative, to represent inflow. This way, you can approximate the correct flow rates and let the head behave as it should based on the system conditions.
Help Documentation section: "Positive Displacement Pumps"
Changing or forcing a pattern of hydraulic grade or flow during a transient simulation