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Members:
Dr. Paul S�nchez Scientific Advisors: Dr. Patrick Richard  |
Research:
Granular systems are widespread in nature. The ability to understand and control their dynamical behaviour is of central importance in numerous industrial processes. Humans have been handling granular materials from the beginning of civilisation. Earth is an enormous source of granules. This is self evident when we observe nature and find sand dunes in the desert, ripples on the shores of beaches, wind and sand causing erosion and creating more sand, and avalanches formed by sand, rocks, water, snow and everything else in its way. Humans, too, have generated a range of granular materials: cement, salt, sugar, coffee, gun powder, flour and many others. However, granular materials are not constrained to small particles, vehicles and asteroids and even people can be placed in this category. All these may be considered as granular materials. The importance of granules does not come only from their prevalence around us, but also from our handling of them. Handling means packing, transportation, sorting, storing, mixing and others. Packing and storing involve a static arrangement of objects. Transportation, sorting and mixing on the on the other hand, have to do with the motion of these objects. Maybe the most important characteristic that places a difference between granular materials and all other known materials, is the ability that grains have to dissipate a great amount of their kinetic energy in a very short period of time. This dissipation is possible due to the inelastic nature of their collisions and the existence of friction between the colliding particles. Friction in turn facilitates the formation of static arrangements of grains. Dissipation causes the wide variety of behaviours that make granular materials to be thought of as the ``4th state of matter.'' Depending on the kinetic energy of the grains, a conglomerate of them may adopt the behaviour of a solid, a liquid or a gas. A set of grains behaves as a solid when at rest. If the grains are more kinetically active, their behaviour resembles a fluid. A greater kinetic activity gives raise to a gas-like behaviour. |
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