Numerical analysis of Newtonian and non-Newtonian ferrofluid pipe flow under constant and oscillanting magnetic fields

Abstract

In this study the effects of constant and oscillating magnetic fields on axi symmetric laminar pipe flow are studied. The analyses cover both Newtonian and non-Newtonian ferro fluids exhibiting both shear thinning and shear thickening effects. The magnetic field is created by a current carrying conductor laying along the axis of the pipe and the magnetic force is implemented to the momentum equation. The first part of the study covers the constant magnetic field and the second part covers oscillating magnetic field cases. The effect of the constant magnetic field on magnetic entrance length, friction factor and velocity profiles are studied. The constant magnetic field and power law index have a decreasing effect on magnetic entrance length for both non-Newtonian and Newtonian fluids, however the Reynolds number is directly propor tional with the magnetic entrance length. The friction factor is directly proportional with the induced magnetic field and the power law index whereas it is inversely pro portional with the Reynolds number. Also flatter velocity profiles are observed under magnetic effects. Compared to constant magnetic field, wavy flow patterns form under oscillating magnetic fields and further increasing the magnetic field strength leads to the development of vortices in the pipe. Compared to constant magnetic field, higher gradients of oscillating magnetic field creates higher magnetic effects as a results higher vorticity values are obtained. Non-dimensional vorticity values reveal that the vorticity is directly proportional with the induced magnetic field and inversely proportional with Reynolds number and power law index.