CFD modeling of turbulent flow for Non-Newtonian fluids in rough pipes

Abstract

Non-Newtonian fluids are pumped under laminar and turbulent regimes through pipes in numerous industries. Proper calculation of pressure losses is essential to optimize available horsepower. In actual practice, no pipe surface is smooth. Pipe roughness has significant influence on the pressure loss for turbulent flow. In this study, a mechanistic model is developed to predict pressure losses of Herschel-Bulkley and Power-Law fluids in rough pipes for the turbulent flow regime. A numerical scheme is applied to the proposed model to obtain an approximate solution. The proposed model is separated into two sub-problems in order to obtain a numerical solution. One is solved analytically for the viscous sublayer, which is determined by pipe roughness and the other is solved numerically by the virtue of the central difference approximation along with the frozen non-linear term for the turbulent core region. Moreover, an experimental study is conducted using two different high viscous polymer base fluids with two different concentrations and three different rough pipe diameters. The mechanistic model results are compared with experimental data in this study and presented by Subramanian (1995). Absolute Average Percent Error (AAPE) of 13.3% is calculated for the proposed model compared to experimental measurements.