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Fluids and Shear Stress

  1. Feb 22, 2009 #1
    1. The problem statement, all variables and given/known data
    A plate sitting on the surface of oil with thickness (y) and viscosity (u) moves with speed (Vo). The velocity profile is a parabola with oil at the plates having the same velocity as the plates. Find the shear stress on the plate from the oil. Repeat problem but with a linear velocity profile.

    2. Relevant equations
    t(shear stress)=u*(dV)/(dy)
    or V=md^2+c

    3. The attempt at a solution
    I'm actually studying for a test and have been given answers but not solutions. The answers are as follows: For a parabolic profile, t=u*Vo/(2y). For linear profile, t=u*Vo/y. Here goes the attempt. dV=Vo-V and V=0 so dV=Vo. but dy I cannot solve (at least not the correct answer). Unless it is simply at the plate, y=y^2, making dy=2y...but I don't see the logic behind that.

    Any help is greatly appreciated.
  2. jcsd
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