1.3.2 Power Law Model
According to the [3], a fluid that obeys the Power Law model is one which can be characterized using the two parameter rheological model of a pseudo plastic or shear thinning fluid. A shear thinning fluid is one in which the viscosity of the fluid decreases as its shear rate increases. The power law model can be described arithmetically as shown below.
\(\tau\ =\ \ \left(\gamma\right)^{n}\text{\ \ \ }\) (4)
\(where,\ \tau\ =shear\ stress\),\(\gamma=shear\ rate\),\(n=exponent\) and \(\ =consstency\ \)
However, Herschel and Bulkley developed another model based on the power law model and this was known as the Yield power law model [5]. The yield power law model merges the theoretical aspects of the Bingham plastic model and the practical aspects of the power law model.