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Pressure theory applied to a Venturi tube

  1. Jul 15, 2012 #1

    I'm a little confused about the pressure in the inlet/outlet and the throat of a Venturi tube.

    Why is the pressure in the inlet/outlet greater than in the throat? I thought that because air is needed to flow into a smaller space so the pressure has to be greater?

    Pardon me. I've self-learning.

    Thanks for your time.
  2. jcsd
  3. Jul 15, 2012 #2


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    welcome to pf!

    hi extricate! welcome to pf! :smile:

    it's conservation of energy (density) …

    Bernoulli's equation is simply a conservation of energy (density) equation

    (and pressure is energy density: pressure = work done per displaced volume = energy per displaced volume)

    where the tube is narrower, the speed is faster, so the kinetic energy density is greater

    so the pressure must be less :wink:
  4. Jul 22, 2012 #3
    Thanks alot for the reply.
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