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Which fluid is more viscous

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data
    Which fluid is more viscous at moderate to high Reynolds number if used in this situation? Air or Water? The flow is incompressible and has velocity V and size L.

    2. Relevant equations

    Re = inerial forces/viscous forces = rho*V*L / mu

    as Re approaches infinity, viscosity approaches zero

    3. The attempt at a solution

    I know that if Re is high, inertial forces dominate. Therefore, viscous forces are small.

    inertial forces / Re = viscous force => wouldn't water always be more viscous assuming the same Re, V, and L is used for both air and water?

    I think there is more to this problem that I am missing. Thanks for any help.
  2. jcsd
  3. Nov 11, 2009 #2


    User Avatar
    Science Advisor

    Sounds good to me. Plus the problem states that the flow is incompressible which intuitively would rule out air.

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