Reduction of Drag Experienced by a Disk Rotating in Viscoelastic Polymer Solutions under Laminar Flow Conditions

Abstract

A disk slowly rotating in a pool of viseoelastie polymer solution experienees a torque lower than it does in an inelastie liquid of the same viseosity. It is suggested that this reduetion of frietional drag under laminar flow eonditions is due to the reversal of the seeondary (radial) flow and a simple model is proposed. Laser Doppler anemometry was used to measure the primary and seeondary velocity profiles around a disk rotating in solutions of polyvinylpyrrolidone and polyacrylamid and the experimentally obtained values of radial and tangential velocity gradients were used to predict the reduetion of frictional resistanee. These predietions are eompatible with the experimental data of D. D.