RUI: Granular Friction, Fluid Mixing and Related Nonlinear Phenomena

9704301 Gollub这是一个更新项目，将利用小型实验室实验和本科生参与，扩大我们对非线性物理现象的理解，特别是涉及颗粒材料和流体的物理现象。将对颗粒层中的剪切摩擦现象进行广泛的研究。精细的剪切力测量将与同时进行的显微成像相结合。这些改进将使粘滑运动的开始、前兆和向连续滑动的转变得到详细的研究。一个目标是比较和对比颗粒摩擦和固体-固体摩擦。第二个重点将是研究流体混合现象，即被动杂质被流动混合的现象。这些实验将包括研究随机细胞流中的混沌平流，以及颗粒介质中的输运。最后，关于非线性波的花样形成和动力学的继续实验将探索具有多空间周期的六方超晶格花样等现象。这是一个更新项目，它将扩展我们对可能导致复杂或不可预测行为的非线性物理现象的理解。该项目将利用小规模的实验室实验，特别关注颗粒或颗粒材料和流体。本科生的科研能力培养将是这项工作的一个重要方面。将对颗粒材料层在剪切力作用下的运动进行广泛的研究。颗粒层中的剪切摩擦在地震中具有潜在的重要意义，尽管这些研究的目的是为了达到基本的理解。精密的测力将与光学成像相结合，以了解突然滑动事件的开始，以及在重大事件之前发生的局部前兆。第二个研究领域将涉及流体混合现象，即被动杂质通过可能包含沙子等多孔介质的流体流动或混合。这类研究可能与杂质在土壤中的传输有关。***

9704301 Gollub This is a renewal project which will extend our understanding of nonlinear physical phenomena, especially those involving granular materials and fluids, using small scale laboratory experiments and involving undergraduate students. An extensive study will be made of the phenomena of shear friction in granular layers. Delicate shear force measurements will be combined with simultaneous microscopic imaging. These improvements will allow the onset of stick- slip motion, precursors, and the transition to continuous slipping to be investigated in detail. One goal is to compare and contrast granular friction with solid-solid friction. A second focus will be the study of fluid mixing phenomena, in which a passive impurity is mixed by a flow. These experiments will include investigations of chaotic advection in random cellular flows, and transport in granular media. Finally, continuing experiments on pattern formation and dynamics of nonlinear waves will explore phenomena such as hexagonal superlattice patterns with multiple spatial periodicities. %%% This a renewal project which will extend our understanding of nonlinear physical phenomena that can give rise to complex or unpredictable behavior. The project will focus especially on granular or particulate materials and fluids, using small scale laboratory experiments. The training of undergraduate students in research will be an important aspect of this work. An extensive study will be made of the motion of layers of granular material when subjected to shear forces. Shear friction in granular layers is potentially important in connection with earthquakes, though these studies are aimed at achieving a basic understanding. Delicate force measurements will be combined with optical imaging to understand the onset of sudden slipping events, and the localized precursors that occur in advance of major events. A second area of study will involve fluid mixing phenomena, in which a passive impurity is transported or mixed by a fluid flow, which may contain a porous medium such as sand. Studies of this type may be relevant to the transport of impurities in soils. ***