Transitional and Turbulent Pipeflow of Pseudoplastic Fluids

A modified mixing length model is developed which permits the computation of velocity distributions and frictional pressure losses for transitional and turbulent pipe flow of viscous, inelastic non-Newtonian fluids. The rheological model assumed is the empirical power law. The method represents an improvement over previous workers' results. The data of several authors, most of which could not be harmonized by previous models, are shown to be fully compatible with the present method. The Dodge-Metzner-Reed, generalized Reynolds number method of correlation is shown to be inappropriate for transitional and turbulent flow. It is further shown that acceptable models of transitional and turbulent flow must correctly account for Theological behavior of the fluid. The proposed method expressly excludes viscoelastic effects. The method is suitable for engineering pipeline design computations and requires only a knowledge of power-law index n to permit computation of velocity profiles and friction factors.