Power Law Model
Test data from a rheometer of several test fluids are considered to be described by the power law relationship:
\tau=k\dot{\gamma}^{n} (9.11)
If the consistency parameter k for all the fluids is 0.01 (Nsm^{–2})^n , illustrate the variation of shear stress with shear rate for values of n of 0.9, 1, and 1.1 up to shear rates of 100 s^{–1} .
The calculation of the shear stress is given in Figure 9.8. With the straight line that corresponds to a Newtonian fluid (n = 1), the curve above (n > 1) corresponds to a dilatant while the curve below corresponds to a pseudoplastic (n < 1).