Branched network analysis 2

[cbutt12]

I am currently working on a waterline extension. The extension I am working on taps off the existing main with a saddle tee. The extension will be a dead end and not loop back to the main. Will the extension receive the full flow that the existing main currently has or will it reduce the flow in the existing main and see only a portion of the flow? I haven't been able to find how to analyze this situation. Most books only show you how to handle networks in loops. Any suggestions would be appreciated. Hope I made myself clear. Thanks

 

[BobPE]

cbutt12:

Flow in distribution systems is conserved. The flow in your dead end will be exactly equal to the demad on that main. It will draw the HGL from the main it is connected to and in doing so will lower the HGL in the main the extension is tapped into depending on the headlosses associated with the demand on the dead end. To estimate the HGL in the dead end, one simplistic way is to trace out the path the water would follow and sum the losses along that path.

My thought would be why wouldn't you want to loop the main?

BobPE

 

[LHA]

Don't treat the new system as a loop, treat it as two parallel branches.

Use the known Q and P at the junction. Since the headloss across both branches must be equivalent, Q will split proportionately. Set hL equal then solve for velocity for each. Then Q=Av