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what does the Flow of the pipe between reservoir and junction indicate?

hi bentley ,

i have a question i have a reservoir at elevation 1,582.56 m and a junction  at elevation 1,571.24 m 

the difference betwee them is 20m 

the demand in the junction is a fixed demande of 3300 m3/day (137.5m3/h) (watercad indicated it has a positive pressure of 81 KPa)

and i have a pipe (length 5.6km) with the properties shown in the picture 

MY QUESTION IS: does the flow shown in the pipe is the demanded flow from the junction or is it the flow that is calculated from reservoir to junction ??

because in my calculation it is not possible for this pipe (250 mm ) with C=150 the flow is lower than the flow indicated in the pipe (not criticizing but i need to know what this flow is indicating in the pipe ) (and please correct me if i have wrong calculation )

thx , with respect :)

  • It is the flow calculated for the downstream of the pipe

  • Joseph,

    WaterCAD uses a demand-based numerical solver that balances energy in the network based on the assumed physical properties, boundary conditions (known HGL at tanks and reservoirs) and assumed demands. So, in the case of a network consisting of Reservoir > Pipe > Junction, the flow in that pipe will be equal to the demand on the junction (unless the demand is configured to be pressure dependent). In other words, the demand and the reservoir HGL are knowns in the equation and the model solves around them. So, the flow is essentially forced through the pipe in order to meet your assumed demand, and the resulting headloss at that flow determines the HGL (and pressure) at the end node.

    If you solve the Hazen Williams equation with these assumptions, the results should match. See below example FlowMaster worksheet.


    Regards,

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

    Answer Verified By: Joseph Daou