Levich Institute Seminar Announcement, 11/08/2005
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Douglas Durian
University of Pennsylvania
Department of Physics
"Partition of Energy for Gas-Fluidized Grains"
When subjected to large forces, materials like foam and sand can unjam and flow much like a liquid. The randomness of the packing then gives rise to random motion at the bubble- or grain- scale. Such dynamics can be described by an effective temperature, for example by the fluctuation near!) equilibrium, other definitions based on fluctuation-response should give different values. In this talk I will describe an athermal system where, remarkably, these are all equal: an 2D gas-fluidized bed consisting of spheres rolling on a flat screen due to an upflow of gas. I will show how the thermal analogy can be exploited to study turbulence, and turbulence-mediated interactions. And I will show how the thermal analogy can be systematically broken by variation of a control parameter.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:
My general research interests are in the area of "soft matter physics": the structure, dynamics, and macroscopic behavior of a very broad and general class of materials that are typically noncrystalline and composed of macromolecules such as polymers, liquid crystals, surfactants, or biomolecules. This growing field complements solid state and statistical physics, and has considerable overlap with disciplines of chemistry, chemical engineering, materials science, and even biology. A common theme in soft condensed matter is that while the materials are disordered at the molecular scale and homogeneous at the macroscopic scale, they usually possess a certain amount of order at an intermediate, or mesoscopic, scale due to a delicate balance of interaction and thermal effects. The general goal is to determine this structure and its dynamics, how it arises, and how it influences the macroscopic behavior. This is obviously of great practical interest, since almost all matter we encounter in our everyday lives is a form of soft condensed matter. This is also of great fundamental interest since while we understand the physics controlling the behavior of individual atoms and molecules, and the physics controlling the behavior of macroscopic chunks of matter, we are relatively ignorant of the complex connection between these well known limits and completely new and unexpected behavior often arise.