RUI: Granular Materials, Fluid Mixing, and Related Nonlinear Phenomena

Haverford College, Haverford PA

Investigators

Abstract

This project aims at extending our understanding of nonlinear physical phenomena, especially those involving granular materials and fluids, using small scale laboratory experiments and involving undergraduate students. For granular materials, both macroscopic stress and microscopic motion will be determined utilizing sensitive force measurements and rapid tracking of large numbers of particles. Specific experiments include: (a) A study of rotationally sheared and air-fluidized granular material, to determine how momentum and energy are transported; (b) Studies of frictional dynamics of planar layers, e.g. of the influence of particle properties on static strength and motion; (c) Experiments on avalanching and flows in inclined layers. The behavior of granular materials will be compared with that of conventional solids and liquids. Some of these experiments have applications to understanding geophysical phenomena. A second focus is the study of fluid mixing phenomena, especially the dramatic differences between mixing in chaotic and turbulent flows. Precise imaging methods will allow a determination of the factors controlling efficiency in mixing and transport, with and without chemical reaction. The project involves both undergraduate students and a postdoctoral trainee, who will be well prepared for a career in which both undergraduate teaching and research are important. %%% This project aims at extending our understanding of nonlinear physical phenomena, especially those involving granular materials and fluids, using small scale laboratory experiments and involving undergraduate students. Granular materials exhibit a transition between solid and fluid states that has important consequences for understanding earthquakes and avalanches, and for the industrial processing of materials such as pharmaceuticals. In the experiments to be conducted, the granular material will be sheared or excited in various ways, and both the internal forces and particle motion will be studied quantitatively. Tests of recent theories will be made in order to understand and predict how these materials flow, and the internal forces they can sustain. A second focus is the study of fluid mixing phenomena, where an impurity is gradually dispersed in a fluid. Understanding the dramatic differences between mixing in chaotic and turbulent flows is an important goal. Precise imaging methods will allow a determination of the factors controlling efficiency in mixing and transport, with and without chemical reaction. The project involves both undergraduate students and a postdoctoral trainee, who will be well prepared for a career in which both undergraduate teaching and research are important.