Mixing of non-Newtonian fluids in time-periodic cavity flows

Fluid mixing in two- and three-dimensional time-periodic cavity flows as a function of rheological fluid parameters is studied. Computational methods are applied to obtain accurate descriptions of the velocity fields, which f orm the basis of the mixing analysis. In addition to some classical techniq ues, like Poincare maps and the analysis of periodic points, a recently dev eloped mapping method is used to determine mixing efficiency over a wide ra nge of different flow parameters. Within this framework, different mixing p rotocols can be evaluated with respect to their long term mixing behaviour and compared quantitatively. It is shown that local 'optimal' parameter set tings for mixing of Newtonian fluids can result in a considerable worse mix ing behaviour for non-Newtonian fluids, and vice versa, illustrating the im portance of taking the rheology of the fluid into account. (C) 2000 Elsevie r Science B.V. All rights reserved.