Reporting the Darcy-Weisbach Friction Factor (f)

Product(s): WaterGEMS, WaterCAD, HAMMER
Version(s): 10.02.02.06
Area: Output and Reporting

Problem

How can I view the Darcy-Weisbach Friction Factor (f) for my pipes? Only the Roughness Height input value is shown.

Solution

As of version 10.02.02.6, the Darcy-Weisbach Friction Factor (f) is an intermediate calculation and is not part of the set of results that can be viewed in the user interface. The following article details the process in used to calculate headloss using the Darcy-Weisbach method: Darcy-Weisbach Headloss Calculations in Steady State and EPS

Enhancement #1058078 will be considered by Bentley Product Management for a future release. In the meantime, consider the following:

  • Why do you need to view the friction factor? Is it necessary for your analysis and reports, or could you report on the roughness height value and computed friction headloss result field?
  • If you want to analyze friction factors for individual pipes, you can use FlowMaster.
  • You may be able to derive the friction factor using a Formula Derived User Data Extension
  • If you have access to Bentley HAMMER, you may be able to use the Copy Initial Conditions tool to view the friction factors. Note that the friction factor reported with this method considers all losses across each pipe, including minor losses.
    • Open your WaterGEMS model and compute a steady state initial conditions simulation
    • Click Tools > Tools > More > Copy Initial Conditions > OK.
    • Select "true" for the attribute called "specify initial conditions?" in the transient calculation options (Analysis > Calculation options > Transient.)
    • Now in the properties (and flextables) for pipes, you will see the field "Darcy-Weisbach f (Initial)" which is based on the headloss through the pipe in the steady state simulation.

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