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Homework Help: Laminar Flow Due To Gravity

  1. Sep 22, 2015 #1
    < Mentor Note -- please remember to use the Homework Help Template when posting schoolwork questions >

    Consider the fully developed laminar flow due to gravity of water in a vertical circular tube. Assume atmospheric pressure at inlet and outlet. Show that the relationship between diameter and Reynold's number is

    D = (32*Re*v2/g)

    I know that Re = ρvD/μ

    I was thinking that perhaps I have to use Bernoulli's equation,
    v12+P/ρ+gz1 = v22+P/ρ+gz2

    But beyond that I'm not sure. Thanks in advance!
    Last edited by a moderator: Sep 23, 2015
  2. jcsd
  3. Sep 23, 2015 #2


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    @emac8585 So what are the things you know about laminar flows and any flow where the Reynolds number makes sense. Then compare that with what you know about Bernoulli's equation and the requirements for its use.
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