Modeling Turbulent Flow of Non-Newtonian Fluids Using Generalized Newtonian Models

Abstract

Computational Fluid Dynamic (CFD) is used to model turbulent flow of non-Newtonian polymeric fluids in concentric annulus. The so called Generalized Newtonian Fluid (GNF) approach is used. Four turbulence models are tested. Applicability of each model in predicting turbulent flow of non-Newtonian fluids in annulus is assessed by comparing results of pressure loss and or velocity profiles with experimental data. The first tested model is a modified version of Lam-Bremhorst k–ε turbulence model. The modification was originally developed to model flow of power law fluids in smooth circular pipes. Results of simulation study showed that this model significantly overestimates the pressure losses. Two k–ε closure type turbulence models, one developed to model turbulent flow of Herschel-Buckley and the other for power law fluids, are shown to fail in predicting turbulent flow of polymer solutions. One of the models contains a damping function which is analyzed to show its inadequacy in damping the eddy viscosity. The last tested model is a one layer turbulence model developed for predicting turbulent flow in annular passages. The model has an adjustable parameter, which is shown to control the slope of velocity profiles in the logarithmic region. It is demonstrated that if the model constant is selected carefully, the model accurately predicts pressure loss and velocity profiles.