Relaxation effects in Couette flow between rotating cylinders

The Couette flow of 0·005, 0·01, 0·025 and 0·05% (w/w) solutions of polyacrylamide in water and of 5% (w/w) solutions of glycerol in water, has been compared with that of water. The coaxial cylinder apparatus used was very similar to that designed by Donnelly. At low rotational speeds of the inner cylinder, the torque on the outer cylinder was proportional to the shear viscosities of the liquid and to the speed of rotation. At a definite value of the Taylor number (Ta) = (Ta)c instabilities occurred; then for (Ta)>(Ta)c drag reduction in the polymer solutions was such that the torque on the outer cylinder was the same as that for the solvent (water). Furthermore (Ta)c (polymer solutions)<(Ta)c (water) = (Ta)c (glycerol solution) = 3390. Equations derived to account for destabilization and drag reduction in tubes are applied to the Couette flow.