EXPANSION FLOWS OF NON-NEWTONIAN LIQUIDS

We consider a number of expansion flows for different non-Newtonian li quids. In the first example, the liquid is an aqueous polymer solution and the expansion flows of interest may be considered to be either tw o-dimensional or three-dimensional. The large vortex activity which is created by fluid inertia is damped by fluid elasticity. In the second group of experiments, a fibre suspension in a Newtonian matrix is inv estigated in both an axisymmetric contraction how and an axisymmetric expansion flow. The vortex enhancement in the contraction confirms ear lier work by other workers. The strong vortex activity in the expansio n (at relatively low Reynolds numbers) is unexpected and provocative. The second part of this paper contains an attempt to simulate the obse rved contraction and expansion hows using a versatile finite-element t echnique which is able to encompass viscoelastic liquids and fibre sus pensions. It is also able to handle three-dimensional hows. The agreem ent between experiment and numerical simulation in all cases is very s atisfactory.