How to manually generate a system head curve

  Applies To 
  Product(s): WaterCAD, WaterGEMS, SewerCAD
  Version(s): CONNECT Edition, V8i
  Area:  Modeling
  Original Author: Bentley Technical Support Group

Problem


How to generate system head curves manually.

Problem number:31824



Solution

Generating a system head curve for the full range of potential flows requires multiple steady-state runs of the model, with each steady-state run representing one point on the curve. The easiest way to arrive at the system head curve is to remove the proposed pump from the model, leaving the suction and discharge nodes in place. For the curve to be computed properly, a tank or reservoir must be present on each side of the pump.

Profile of system for system head curve:



The water that leaves the suction-side pressure zone is identified as a demand on the suction node, while the water that enters the discharge-side pressure zone is identified as an inflow (or negative demand) on the discharge node. The difference in head between the suction and discharge nodes as determined by the model is the head that must be added to move that flow rate through the pump (that is, between the two pressure zones). The flow rate at both the suction and discharge nodes is then changed and the model re-run to generate additional points on the curve, continuing until a full curve has been developed. The Advanced Water Distribution Modeling and Management book has additional details on this.

See Also

Understanding System Head Curves in WaterGEMS, WaterCAD, and SewerCAD

System head curve generated in WaterGEMS, WaterCAD, or SewerCAD looks different from hand calculations

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