EXPLANATION OF SPURT FOR A NON-NEWTONIAN FLUID BY A DIFFUSION TERM

A surprising feature of the flow of polymers is associated with a sudden increase in the volumetric flow rate when the pressure gradient is gradually increased beyond a critical value. This striking phenomenon, called 'spurt', was apparently first observed by Vinogradov et al in rheological experiments involving the flow through thin capillaries of highly elastic and very viscous non-Newtonian fluids like some synthesized polybutadienes and polyisoprenes. Much effort is being spent to explain spurt and related phenomena mathematically. The spurt phenomenon is dynamic and cannot be explained in a satisfactory manner by only studying the steady-state equations. Dynamical theory can explain phenomena observed in experiments and in numerical simulations, and it can also predict phenomena like latency, shape memory, and hysteresis which should be observable in future experiments. In this paper we add a diffusion term to the constitutive equation. (from Authors)