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Homework Help: Shear Stress due to Laminar flow

  1. Feb 3, 2007 #1
    1. The problem statement, all variables and given/known data
    Oil of Density 888kg/m^3 and viscosity 0.8Pa*s is flowing in a horizontal pipe of diameter 0.15m. The local flow velocity at the centerline is 10m/s. find the shear stress exerted by the oil on the wall of the pipe.

    2. Relevant equations
    tau = -eta*(dv/dy)

    3. The attempt at a solution
    = -0.8*(10/0.075) = 106.7 Pa
    but the given solution is 213Pa, exactly twice my answer, what am I doing wrong? thanks
  2. jcsd
  3. Feb 4, 2007 #2


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  4. Feb 4, 2007 #3


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    As AlephZero stated, you should find a velocity function v(y) as a polynomial of degree 2 satisfying the given velocity condition in the middle streamline.
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