Bad or unstable results with Flushing

  Applies To 
  Product(s): Bentley WaterCAD, WaterGEMS
  Environment:  N/A
  Area:  Calculations
  Original Author: Jesse Dringoli, Bentley Technical Support Group


When computing a flushing analysis and examining results using the Flushing Results Browser, results look questionable (such as extreme pressures, flows that do not seem to make sense, etc) or it is apparent that the model was not balanced. A steady state check provides good results however.


This may occur in rare cases due to a slight difference in how convergence is calculated with the Flushing analysis when compared to a "normal" model run (with calculation options set the same). In the rare event that such differences cause a model to become unbalanced (which can happen if the model is very sensitive or right on the verge of non-convergence) you should be able to address the issue by increasing the maximum trials. This is found in the calculation option set assigned to the flushing representative scenario. The default "trials" is 40; try increasing this to 50, 100 or if needed, higher. In extreme cases, you may also need to adjust other advanced calculation options such as the damping limit. (more on those below)

Note that future releases will include improvements to reduce the chances of this issue.

See also

See Also

Engine Compatibility mode and Calculation Options