Concentric annular flow with centerbody rotation of a Newtonian and a shear-thinning liquid

Abstract

Measurements of the radial distributions of the axial and tangential components of velocity and rms velocity fluctuations are presented together with friction factor versus Reynolds number data for two liquids, one Newtonian, the other a shear-thinning polymer, in laminar, transitional, and turbulent flow in an annular geometry with a rotating centerbody of radius ratio 0.506. In all flow regimes, the friction factor is increased by centerbody rotation. However, the influence is slight and most apparent for laminar flow of the Newtonian fluid. Laser Doppier anenometry (LDA) measurements of the tangential velocity reveal three distinct regions across the radial gap with a central region of almost constant angular momentum, which diminishes in magnitude as the Reynolds number increases. Axial velocity measurements show only slight deviations from what would be expected for the case without centerbody rotation. In turbulent flow, the axial velocity fluctuations decrease progressively with increasing Reynolds number for all fluids. For the polymeric liquid, the tangential velocity fluctuations are somewhat suppressed, especially at high Reynolds numbers where the influence of centerbody rotation is reduced. Over a limited range of (low) Reynolds numbers and rotation speeds, the generation and advection of Taylor vortices produces complex flow patterns. Limited measurements are reported for the vortex advection speed.