Abstract
A generalized rheological model for shear thinning fluids has been developed. The new model relates shear stress to shear rate for this type of fluids and predicts the behaviour of hyperbolic, parabolic, elliptic, and Newtonian fluids with or without yield stress at one or both extremes of the shear rate. It correlates the shear stress to the shear rate for a variety of drilling fluids better than both the power-law and Hershel—Bulkley model. It can also predict the viscosity of these fluids. The shear stress and viscosity are required for pressure drop calculations of flow in pipes, annuli, and packed beds.