Models for the Viscosity of Non-Newtonian Fluids

The most effective model for non-Newtonian flow is the Ostwald-de Waele two-parameter, power-law fluid model [13]. The popularity of this model is easily traced to its Iractability in mathematical manipulations. In the power-law model, the apparent viscosity y = j. l CM Idy = r/y of a polymer fluid subject to a simple steady shear flow is given by 

K has units of Pa s in the SI system and is termed the fluid consistency n is a dimensionless number related to the shear-thinning exponent introduced earlier and is termed the power-law index 

FIGURE 7.4 Flow curves for a commercial sample of polystyrene at various temperatures obtained using capillary rheometry. 

FIGURE 7.5 Flow curves for six concentrations of polyacrylamide in water. The lines through the data are model predictions. (Data from Rodriguez, F. and L. A. Goettler, Trans. Soc. RheoL, 8, 3, 1964.) 

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