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System curve for open ended pipe system.

System curve for open ended pipe system.

System curve for open ended pipe system.

(OP)
I understand how to develop a system curve for a closed water piping circuit, however, I am trying to predict drop in squirt height from a small orifice at the end of a piping run that is supplied with water from a header tank that is draining out (falling head pressure).
My question: Is the relationship between the static head from the tank and the residual squirt height from the orifice linear or parabolic?
In the formula: Head = K.Flowrate*2 used to calculate the system curve, is the head used in the above formula the total head required to push the water through the pipe and orifice and produce a squirt height OR is the head the difference between the total head from the tank and the residual squirt height? Is it possible to develop a system curve using just one operating point? Ideally, once I have the system constant K, I want to graph the Static Head vs. Squirt Height (for varying values of K).
FYI this is for septic system pressure fields fed from a higher elevation by a gravity discharging dosing tank (no pump required).

Thanks, JohnLR

RE: System curve for open ended pipe system.

Only the pressure at the tank outlet will be dependent on height of fluid in the tank. With that as the inlet pressure and approximately zero at the outlet, you should be able to calculate the flowrate. The flowrates will not be linear, the velocity will not be linear, nor will the trajectory, even without a piped outlet. Note that if the pipe drops below the top of the discharge pipe (at its inlet, or elsewhere), you will only have a partial flow in the pipe and may have to change head loss equations to those applicable to gravity flow. Then you can plot those flowrates against the the height of liquid in the tank.

The system curve for one operating point is ONLY one point.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

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