Cavitation effects in eccentric-cylinder flows of Newtonian and non-Newtonian fluids

The paper contains an account of the effects of viscoelasticity on cavitati on characteristics observed when liquids are sheared in the gap between ecc entric cylinders in relative rotation. To facilitate the Study, flow-visual ization experiments are carried out on Newtonian fluids and also constant-v iscosity highly elastic Boger fluids. For low speeds, the free surface in the liquids is seen to depart progressi vely from the initial horizontal (rest) configuration, this to ensure that no negative pressures exist in the liquid. With further increases in rotati onal speed, a provocative fingering mechanism appears, which generates a se ries of cavities, the number of which increases with rotational speed and e ccentricity. The elastic liquids are found to generate more cells than thei r Newtonian equivalents. Another feature of interest concerns the shape of the cavities, where the elastic liquids exhibit distinctive CUSP-like extre mities, in contrast to the smooth shapes observed in the corresponding Newt onian experiments, (C) 2001 Elsevier Science Ltd. All rights reserved.