HYDRODYNAMICS OF CHANNEL CONFINED ROTATING CIRCULAR CYLINDER SUBMERGED IN NON-NEWTONIAN MEDIA

Abstract

The present investigation aims to study aims to study the hydrodynamics of channel confined circular cylinder submerged in non-Newtonian fluid. The applications involve rotary drum drying, filtration of slurries, offshore drilling, calendaring and sheet making process in polymer, paper making etc. The study is carried out for wide ranges of conditions as: 0≤α≤2, 1≤Re≤40, 0.4≤n≤1.8 and β = 10. It aims to demonstrate flow behavior and hydrodynamics of a non-Newtonian fluid whose rheology is governed by power-law model across a rotating cylinder in confined channel. It mainly focuses on the influence of rotation of cylinder in presence of wall effects on drag and lift forces experienced by cylinder. An enveloping vortex appears in the flow patterns from n=0.8 onwards for rotating cylinder, the thickness of this vortex intensifies as values of n and α are increased while its thickness drops down as inertial effects are increased. A small wake region behind the cylinder first appears at Re=5 for stationary cylinder in case of shear thickening fluid, which soon transform to rather bigger twin-vortex as Re increases. For rotating cylinder as Re reaches 20, a single vortex region is obtained behind cylinder, the size of which increases with n. As rotational speed is increased the size of this vortex increases for shear thickening fluid whilst an opposite trend is obtained for shear thinning fluid. The pressure drag coefficient decreases as n increases for constant Re and 𝛼, it further drops down as Re and 𝛼 are increased. For constant Re and α, frictional drag coefficient increases with n while it decreases as Re and α are increased. The total drag coefficient decreases with Re for constant n, rotation of cylinder augments this effect. The lift coefficients decrease with Re, while increase with 𝛼 for constant 𝑛. For a constant Re, Frictional lift coefficient increases with n and rotation of cylinder further augments this effect. The pressure lift coefficient decreases with n for all 𝑅𝑒.