Discharge from Horizontal Pipe
Discharge from Horizontal Pipe
(OP)
Why can't i find a nice equation to determine discharge from a horizontal pipe? All I can find are formulas that want to know the height of the pipe off the ground and how far the water "shoots" out. Isn't there a nice equation based on pipe diameter and differential pressure? I've seen such equations for nozzles, but never for an open pipe.





RE: Discharge from Horizontal Pipe
You're asking the same question as how long will a sky diver take to hit the ground. It of course depends on how high he was before he opened the chute.
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BigInch
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RE: Discharge from Horizontal Pipe
RE: Discharge from Horizontal Pipe
it is all there.
saludos.
a.
RE: Discharge from Horizontal Pipe
RE: Discharge from Horizontal Pipe
If the pipe is horizontal and flows full, you do not need to know the height off the ground.
If you know the differential pressure--- the pipe inlet and pipe exit pressure then set the differential with proper units equal to rho*v^2/2*(fL/D).
I assume you know what rho,L,V and D are. Any good fluids text will have a chart for f versus pipe size (ID) and relative roughness/ pipe material as a function of Nre.
Regards
RE: Discharge from Horizontal Pipe
I happen to know that the 7th ed. of the “Civil Engineering Reference Manual” by Lindeburg just a few years ago published essentially the same discharge equation as the old Crane, and additionally showed a matrix of several different “orifice” illustrations and coefficients. While this isn’t necessarily explained in (the some practical?) terms of simple discharge out of the free plain end of a length of piping as did old Crane, I noticed that Lindeburg does show a value of C for his condition “D” orifice (that is illustrated as a short flange by plain end looking orifice, with flow direction to discharge out the plain end) of 0.82. Whether intended or not it appears this agrees quite closely to my crude re-visiting of the ancient Crane nomograph for a discharging pipe. I would be interested if any others feel this is a reasonably correct look at this issue.
RE: Discharge from Horizontal Pipe
If you want to calculate the GPM for the discharge, the first thing to recognize is that the GPM is exactly the same all along the pipe, even if it changes diameter. You need to balance the pressure supplied by the pump or gravity (or both) against the pressure drops through all the different factors such as static height, pipe friction, valves, fittings and finally (and usually least) the discharge velocity head. When these are in balance you have the correct GPM. QED.
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RE: Discharge from Horizontal Pipe
FHWA HEC-12 has those in easy nomographs, for common pipe sizes and inlet configurations.
Engineering is the practice of the art of science - Steve