Submerged Pipe Discharge Force
Submerged Pipe Discharge Force
(OP)
I need to calculate the downward vertical force exerted on a section of tubing that is submerged and discharging a cold water flow into hot water.
The tubing is 27.125 inches long and is connected to a water supply on one end w/ a flow rate of 3 GPM. The other end is open to a tank of hot water. I am assuming the tube is completely submerged in water. The tube has ID 0.58" and OD 0.65". The tube material is smooth plastic. The flow cycles on and off, so I am assuming the greatest force will be when it first turns on, similar to the jolt felt when a firehose or garden hose first turns on.
I have calculated several different forces several ways (including shear stress along the tube inner wall and momentum flux at the outlet) and everything I get is of minimal value, always <0.1 lbf.
Any sort of help is appreciated.
The tubing is 27.125 inches long and is connected to a water supply on one end w/ a flow rate of 3 GPM. The other end is open to a tank of hot water. I am assuming the tube is completely submerged in water. The tube has ID 0.58" and OD 0.65". The tube material is smooth plastic. The flow cycles on and off, so I am assuming the greatest force will be when it first turns on, similar to the jolt felt when a firehose or garden hose first turns on.
I have calculated several different forces several ways (including shear stress along the tube inner wall and momentum flux at the outlet) and everything I get is of minimal value, always <0.1 lbf.
Any sort of help is appreciated.





RE: Submerged Pipe Discharge Force
i suspect downwards. in that case you first have to overcome the static pressure difference, about 15psi on 0.25in2 (internal area) = 4 lbs.
now 1 gallon = 4.54liters = 4540cc = 277in3 = 0.16ft3
3 gpm = 831in3/min = 14in3/sec
so the flow rate is 56in/sec = 4.5ft/sec
and 3 gpm = 30 lbf/min = 0.5 lbf/sec = 0.0155 lbm/sec
so that the momentum rate (force) = 0.0155*4.5 = 0.07 lbf
(alot smaller than i'd've thought)
RE: Submerged Pipe Discharge Force
Ted