Non-Newtonian effects in axially symmetric rotational flows of some elastico-viscous liquids

Abstract

In recent years new materials of industrial importance have become known whose rheological properties cannot be adequately characterized by the classical Newtonian working model, many of these materials exhibiting both viscous and elastic properties. The large-scale flow behaviour of some of these new materials can be strikingly different from that of purely viscous liquids. For example, when sheared between coaxial cylinders, some liquids are observed to ‘climb up’ the inner cylinder, i.e. the free surface rises spectacularly near the inner boundary. This phenomenon has been observed by many authors (see, for example (1–4)), and is now widely known as the Weissenberg effect. Again, Merrington (5) observed that a stream of rubber solution ‘swells’ radially immediately on emerging from a capillary tube. In order to attempt to explain behaviour such as this, we must examine the consequences of a working model which is more complex than that for Newtonian liquids.