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Viscosity Problem using power law for non-newtonian fluids

  1. Apr 2, 2012 #1
    Problem Statement:
    Blood is a pseudoplastic fluid that has a variable viscosity at 37 °C that depends on the percent composition of hematocrit and plasma. It will usually range between 3 x 10^-3 to 4 x 10^-3 Pa s. A small sample of blood is tested in a viscometer and the following results are obtained:

    (Shear stress (Pa), Shear rate (s^-1))
    (0.0235, 2.25)
    (0.0396, 4.5)
    (0.0787, 11.25)
    (0.1324, 22.5)
    (0.2227, 45)
    (0.3746, 90)
    (0.7447, 225)
    (1.2524, 450)

    Determine the viscosity of the blood sample using the power law for non-Newtonian fluids:


    where τ is shear stress, η is viscosity, γ is shear rate, and n is the flow behavior index.

    I have no idea where to start, since I have two unknowns in this problem. It also seems like the sample would have a different viscosity at each point, but the problem only asks for one value. I am truly lost. Any help or insight would be greatly appreciated!
  2. jcsd
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