ANALYSIS OF CORE-ANNULAR FLOW WITH POWER LAW FLUID IN THE ANNULAR REGION LUBRICATING HIGH-VISCOSITY NEWTONIAN FLUID

This study investigates the dynamics of core-annular flow (CAF) focusing on the interaction between a high-viscosity Newtonian fluid in the core region and a power-law fluid within the annular region of a horizontal pipe. Through a combination of theoretical analysis and computational fluid dynamics (CFD) simulations, the effects of varying power law index of the annular fluid on velocity profiles and pressure drop within the CAF system are explored. The theoretical models are presented for a perfect CAF arrangement without considering the interfacial waves. The simulation studies are performed using ANSYS fluent to predict the flow behavior, velocity profiles, and pressure drop in the pipe having a high viscosity Newtonian core and a power law fluid in the annular region. The simulation studies are performed for three cases of power law index of the annular fluid (<i>n<sub>a</sub></i>): shear thinning (<i>n<sub>a</sub></i> = 0.8), Newtonian (<i>n<sub>a</sub></i> = 1), and shear thickening (<i>n<sub>a</sub></i> = 1.2). The pressure variation along pipe centerline and velocity profiles of the CAF arrangement are presented. It is observed that while the shear-thickening fluid in the annular region slows down the flow of core fluid, a shear-thinning fluid in the annular region assists the core fluid and ensures its more efficient transport in the pipeline. Possible explanations of the observed behavior of pressure drop and velocity profiles are also presented.