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Unformatted text preview: Fluid – rate of strain is proportional to applied stress (N) NonN fluid – rate not constant, doesn’t recover to original form once force is recovered Newtons Law of visc. Tau = mu * dv/dy = delta P*r / 2L dVx/dy = sheer rate, rate of strain, velocity gradient ex. Ethyl alcohol, benzene, hexane, H20 Power rule: tau = m (du/dy)^n pseudo: n <1 polymers dilatant: n>1 dispersions Bingham Plastic Newtonian Power Law (Dilatant) Power Law (Pseudoplastic) Velocity Gradient, du/dy Shear Stress, τ τ o Bingham Plastic: T= T0 + m (du/dy) T0 = mag of stress need to make fluid move For high flow, vessels make large D to put Re in laminar range Turbulent flow in arteries, plaques and lipids will stick to vessel walls Apparent viscosity : Blood is both Newtonian and NN – also thixotropic!!...
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 Fall '08
 Frey
 Biomedical Engineering, Shear Stress, heart rate, NonNewtonian fluid, rate Volume Fraction, Bingham Plastic Power Law

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