12 - Fluid – rate of strain is proportional to applied...

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Stroke volume: volume of blood heart puts out with each beat Cardiac output: stroke volume * heart rate Volume Fraction: RBC – hematocrit High count – not good for circulation Low Count – acts like water emulsion Non newt – pastes, gels Reynolds – ratio of inertial forces to viscous forces – describes laminar vs. turbulent flow R < 2500 laminar; R > 2500 turbulent Thixotropic: viscosity decreases with sheer force and time blood Rheopectic: viscosity increases with sheer force and time Artificial – pyrolytic carbon – clotting and blood thinners infections Porcine – pig valves – veins/arteries are similar in size, causes immune response, immunosuppresants, doesn’t last as long as mechanical valves Zenogenic tissues – no generation/proliferation mechanisms Solid deforms w. applied force – strain is a function of applied stress
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Unformatted text preview: Fluid – rate of strain is proportional to applied stress (N) Non-N 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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This note was uploaded on 11/29/2010 for the course BME 314 taught by Professor Frey during the Fall '08 term at University of Texas.

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12 - Fluid – rate of strain is proportional to applied...

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