On the use of a rotating sphere in the measurement of elastico-viscous parameters

A recent theoretical investigation by Thomas and Walters (1963) has indicated that measurements of the couple on a rotating sphere immersed in an infinite expanse of elasticoviscous liquid could provide a useful means of measuring elastico-viscous parameters. The experimental arrangement would consist of a rotating sphere in a bath of elastico-viscous liquid. The object of the present paper is to determine the minimum dimensions of the bath for the conditions of the theoretical problem to be approximately realized. To facilitate this, we consider the idealized problem of a sphere rotating in an elastico-viscous liquid which fills a stationary concentric spherical container. It is shown that when the ratio of the radii of the two spheres is about 1: 12 the outer sphere has an effect of less than 1% on the couple on the rotating sphere.