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Bernoulli's Pressure Drop Segregated from Friction Pressure Drop

  1. Dec 6, 2006 #1
    Hello Physics Masters!

    I would like to calculate pressure drop values caused by friction as water flows through a a smooth pipe at different velocities and different internal pipe diameters.

    I ONLY want the pressure drop values caused by friction, not the pressure drop values caused by Bernoulli's principle. The mathematical formulas that I have found combine Bernoulli's principle PLUS friction. I only need the friction component.

    Can you direct me to a web site that would have this information, or provide the friction-only mathematical formula?

    Thanks,
    Roger
     
  2. jcsd
  3. Dec 6, 2006 #2

    Hootenanny

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    Perhaps Poiseuille's Law may be of some use to you. The link is taken from the Hyperphysics site, which in my opinion is a good general reference site for physics.
     
  4. Dec 6, 2006 #3

    Q_Goest

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    Hi Roger,
    I suggest you use the Darcy Weisbach equation, as it's the most common one used in industry today. There are others such as Poiseuille's law as mentioned by Hootenann and the Hazen-Williams equation, but they are not used nearly as much as Darcy Weisbach.

    The other question that inevitably follows regards how to determine the equivalent restriction of various piping components such as pipe bends or mitred elbows, valves, orifices, Y's and T's, expansions and contractions, etc.... These are all covered by the Crane Technical paper #410 which is also widely renown as the industry standard for doing pipe flow analysis. The Crane paper relies heavily on the Darcy Weisbach equation.

    If you do much analysis of pipe losses as an engineer, you will need to become familiar with the Crane paper and the methods it outlines.
     
  5. Dec 6, 2006 #4
    Actually I don't think you want a "smooth" pipe as that would imply that there is no surface friction, and the locus of velocity would run perpendicular to its vectorial self.
     
  6. Dec 6, 2006 #5

    FredGarvin

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    A smooth pipe does not imply zero friction. If you look at any Moody Diagram, there is a line for a smooth surface. It is simply a best case surface roughness.
     
  7. Dec 6, 2006 #6
    Well do they call them "smooth" pipes or are they just smooth lines on the diagram? From my education if anything in physics was "smooth", it meant that friction was ignored. Unless perhaps this is some esoteric use of the word specific to engineers?
     
  8. Dec 6, 2006 #7
    Sounds like something specific to your textbook that you used.
     
  9. Dec 7, 2006 #8
    Thanks for your ideas and comments Hootenanny, Q_Goest, billiards, FredGarvin and KingNothing.

    This has helped me a lot.

    Roger.
     
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