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IMA Workshop 5
Particulate Flows: Processing and Rheology
January 8-12, 1996

Heterogeneous materials can behave strangely, even in simple flow situations. For example, a mixture of solid particles in a liquid can exhibit behavior that seems solid-like or fluid-like, and attempting to measure the "viscosity" of such a mixture leads to contradictions and "unrepeatible" experiments. Even so, such materials are commonly used in manufacturing and processing.

Food processing, catalytic processing, slurries, coating, paper manufacturing, particle injection molding, paving and filter operation all involve flow of heterogeneous materials. In many of these processes, the rheology of such materials is a critical element in considerations of design, operation, and efficiency. Also, in many of them, the properties are nonuniform in space and change in time. Consequently, using these materials represents a technological challenge.

One of the fundamental rheological issues is the microstructure and its evolution. A distribution showing pairs and/or clusters will behave quite differently from a random distribution. Further, a mixture with a lattice structure behaves differently also. Relative motions between the material also contribute to different behaviors. Layers of clear fluid can shear easily, while regions with solid particles near the maximum packing limit will behave as a rigid solid or a very viscous fluid. Particle-particle contacts or collisions can affect the rheology.

A judicious mix of physical understanding and mathematical analysis is needed to understand the rheology of particle-fluid mixture. The focus of the workshop is to combine research aimed at physical phenomena with analysis of microscale dynamics and particle distribution functions to build a better understanding of the physics and to develop mathematical models of the phenomena.

(1) Topics: Asphalt, sedimentation, fluidization, particle deposition/drying, particle injection molding, suspension rheology, food rheology, fiberous material/paper, slurries, filter flows, rheology in magnetic coating and other particulate coating.

(2) Methods: Mathematical modeling, Stokesian dynamics, effective media.

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