Circular Couette Flow and Taylor Vortices in Shear-Thinning Liquids

Abstract

The flow structure in a concentric annular geometry with a large aspect ratio and a radius ratio of 0.506 has been investigated for inner cylinder (centrebody) rotation for one Newtonian and two non-Newtonian liquids: glucose, Xanthan gum and a blend of Laponite and CMC. Tangential velocity distributions have been measured for circular Couette flow (i.e. sub-critical Taylor numbers) and found to be in excellent agreement with theory. Tangential and axial velocity components have been measured for high-Taylor numbers to reveal the internal structure of the Taylor vortices. The axial-velocity data have been used to construct streamline plots of the radial-axial flowfields. The shear-thinning nature of the two non-Newtonian fluids is shown to have a strong influence on both the Couette flow and also the Taylor cell structure. Axial drift of the Taylor cells for the two non-Newtonian liquids is attributed to differences in their rheological characteristics (viscoelasticity versus thixotropy).