Velocity of a water jet given water pressure and diameter?

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SUMMARY

The velocity of a water jet exiting a garden hose can be calculated using the formula derived from orifice flow principles. For a 1/2" diameter hose under 40 psi pressure, the velocity can be estimated using the equation: Velocity (ft/s) = 0.32 x GPM / TFA (sq. in.). This approach incorporates the flow rate in gallons per minute (GPM) and the cross-sectional area of the hose. Newton's second law can also be applied to understand the dynamics of the water jet over time.

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  • Understanding of fluid dynamics principles
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  • Knowledge of pressure measurement in psi
  • Basic calculations involving area and flow rate
NEXT STEPS
  • Research orifice flow equations and their applications
  • Learn how to calculate flow rate in gallons per minute (GPM)
  • Study the effects of pressure on fluid velocity
  • Explore Newton's second law in fluid dynamics contexts
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Engineers, fluid dynamics students, and anyone involved in hydraulic systems or water flow calculations will benefit from this discussion.

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I need to determine the velocity of a water jet. For example, if a garden hose is 1/2" in diameter and we assume that the water pressure is 40psi, what would be the water velocity (in ft/s) as it exits the hose (assuming no nozzle)?



We know Pressure = force/area, but I want to know the velocity in feet/second, so I don't know what equation to use!



Since velocity has a time component, would we need to introduce another factor? Maybe estimate the gallons per minute? Is this known for a typical garden hose? Thank you in advance!
 
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You can estimate flow speed from an orifice given just it's size, the presure and a factor that describes the shape.
Have you tried looking up orifice+flow in your textbook.
 
.32 X GPM
_________ = Ft/Sec velocity
TFA (sq. in.)
http://www.uiweb.uidaho.edu/extension/lawn/Files/Garden_Hose.htm
 
Last edited by a moderator:
Use the Newton's second law, considering a small dt amount of time.
 

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