Nearly Viscometric Flow of Viscoelastic Fluids in the Disk and Cylinder System. II: Experimental

Abstract

Radial and tangential velocity distributions are measured for laminar flow of two Newtonian and one viscoelastic fluids in the disk and cylinder system. Velocities are determined from time lapse photographs of small particles suspended in the fluid which is illuminated in thin sections by a collimated beam of light. Measurements are made at Reynolds numbers of 0.0616, 24.4, and 97.6 for the Newtonian fluids and at 0.0371 for the viscoelastic fluid. The distributions are compared with the analyses of Kramer and Johnson in Part I. A toroidal secondary flow is observed which circulates in opposite directions for Newtonian and viscoelastic fluids, and a study of the dependence of the secondary flow direction on fluid properties and disk speed is reported. Complex flow patterns which appear in the region in which the direction of secondary flow changes are described. For Newtonian fluids tangential velocity computations agree to ±5% with the experimental measurements up to a Reynolds number of 24.4, and predicted radial velocities agree with experimental data within 20% at the Reynolds number of 24.4. At a Reynolds number of 97.6 predicted tangential velocities differ from experimental measurements by as much as ±50% while radial velocities differ from experimental values by a factor of two to three. The second order fluid predicts tangential velocities which are twice as large as experimental values and radial velocities which are in error by as much as a factor of six. The WJFLMB model predicts tangential and radial velocities which agree with experiment to within ±20% and ±40%, respectively. A Weissenberg Rheogoniometer is used to measure non-Newtonian viscosity, complex viscosity, and primary normal stress differences of the viscoelastic fluids, and to measure viscosities of the Newtonian fluids.