Biochemical Engineering Fundamentals, Part 1 - Bailey J., Ollis D. 1989

Transport phenomena in biotechnological systems
Non-Newtonian fluids

For fluids, The ratio of shear stress тs to velocity gradient du/dy is defined as viscosity ηv (the subscript v serves to distinguish the viscosity symbol from the previously discussed efficiency coefficient η). Thus,

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For Newtonian fluids, the relationship between т and du/dy is graphically represented by a straight line passing through the origin. Under steady-state flow conditions, various types of non-Newtonian behavior have been observed for polymer solutions and/or disperse systems with a dispersed solid or liquid phase; the most typical forms of this behavior are shown in Fig. 8.12, where the shear rate y is used instead of du/dy.

FIG. 8.12. Shear stress versus shear rate for Newtonian and the most typical models of Non-Newtonian fluids: 1 — Bingham plastic model; 2 — Casson equation; 3 — dilatant model; 4 — Newtonian fluid; 5 — pseudoplastic. [Roels J. A., van den Berg Voncken R. M., The Reology of Mycelial Broth, Biotech. Bioeng., 16, 181 (1974).]



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