Mixing of Non-Newtonian Fluids in Steadily Forced Systems

We investigate mixing in a viscoelastic and shear-thinning fluid—a very common combination in polymers and suspensions. We find that competition between elastic and viscous forces generates self-similar mixing, lobe transport, and other characteristics of chaos. The mechanism by which chaos is produced is evaluated both in experiments and in a simple model. We find that chaotic flow is generated by spontaneous oscillations, the magnitude and frequency of which govern the extent of chaos and mixing

Flowsheet modeling of the compression step of a continuous wet granulation production line

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Monte Carlo calculation of effective diffusivities in two- and three-dimensional heterogeneous materials of variable structure

A Monte Carlo technique that simulates tracer diffusion in multiphase materials of arbitrary complexity has been developed. Effective diffusivities are calculated for structures consisting of either overlapping or nonoverlapping inclusions with diffusivity Dc, distributed in a continuous phase with diffusivity D0\u3eDc. Two-dimensional simulations for various values of D0/Dc generate normalized diffusivities that correspond closely to their three-dimensional counterparts; they nearly collapse to a common curve when a simple scaling relation is applied

Non-uniform stationary measure properties of chaotic area-preserving dynamical systems

This article shows the existence of a non-uniform stationary measure (referred to as the w-invariant measure) associated with the space-filling properties of the unstable manifold and characterizing some statistical properties of chaotic two-dimensional area-preserving systems. The w-invariant measure, which differs from the ergodic measure and is non-uniform in general, plays a central role in the statistical characterization of chaotic fluid mixing systems, since several properties of partially mixed structures can be expressed as ensemble averages over the w-invariant measure. A closed-form expression for the w-invariant density is obtained for a class of mixing systems topologically conjugate with the linear toral automorphism. The physical implications in the theory of fluid mixing, and in the statistical characterization of chaotic Hamiltonian systems, are discussed. (C) 1998 Elsevier Science B.V. All rights reserved