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Comparing field and model data

From the following Bentley YouTube tutorial àhttps://www.youtube.com/watch?v=llA0Dud9R_E&list=PLLCOESNdmKSJAaqcqkfZJqw4eIEpB-NAC&index=10

It’s explained that one should “compare hydraulic grade lines between the field and the model”. And gives the following illustrations to as an example of why comparing model to field using hydraulic grade line is better then comparing pressures.
       

My question is then the following:
What does location portrayed on the X-axis stand for? Is it the distance from the source in terms of:

  • Difference in elevation between source and measurement point or
  • Pipe length between source and measurement point
  • The "Location" axis represents the distance along the pipeline (station). 

    As you move along a length of pipe the pressure can jump around because the elevation from which is is observed can change (and that elevation may not always be accurately measured), whereas the HGL is not influenced by the elevation and changes due to headloss (friction) or head gain (pumps).


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Ok but for example in the image above the distnace/location of the node in the green circle is straight forward you could simply count the lengths of the pipes between that node and the resercoir (if i'm understanding you correctly). But what about the node in the red circle? There are 2 paths from the reservoir to that node so what would be the distance/ location of the node in the red circle.

  • There would be multiple paths to the node in red. I think the point that the graph is trying to make is that as you move downstream along any given pipeline (whether it's the one on the left side or the right side leading to the red circled node does not matter as long as the flow is in the same direction toward the red node), the HGL will gradually decrease due to headloss since it is independent from the elevation, whereas the pressure at the same line of pipes could jump around as the elevation changes.

    So, when comparing model results to field measurements, it is best to compare HGL so that uncertainty from elevation (point of pressure measurement) is not a factor.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  •  In the video there is something else that is confusing. It is recommended that pressure  measurements be taken at the perimeters of the system away from system form tanks form example (see image below taken from set tutorial)

    But if measurements are only taken at the perimeter ( like the blue dot in the image above) of the system and not at intervals between the perimeter and the tank one can not really get enough results to create a e graph like the one in the image below? So there aside from measuring at the perimeters on should also measure at intervals between form example tank and perimeter right?

  • And then also when conducting a hydrant flow test the residual hydrant does not necessarily need to be a hydrant right? A logger placed somewhere else that is not a hydrant should not make a difference right?