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Why pressure is lower at the small bore of a venturi

  1. Mar 30, 2010 #1
    Hi, why is it that in a venturi system the pressure is lower when the diameter of the cross sectional area is smaller?

    I do not understand why pressure can be considered a form of "energy". I can understand that energy must be conserved and due to the reduction in the diameter the increase in speed (K.E increase) means a reduction in this pressure energy

    Can someone please help me get my head around why this is the case?

  2. jcsd
  3. Mar 30, 2010 #2


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    Science Advisor

    It's considered energy because it requires work for the fluid to flow...i.e. pressure times volume equals work. You could also rewrite it as pressure time area = force, and force times distance = work. Since area times length (distance) is volume, pressure times volume equals work. Which means it requires energy in the form of pressure acting on a volume of fluid to get it to flow.

    So if you look at the Bernoulli equation the first term would be the "pressure head" and is representative of this energy.

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