RUI: Granular Friction, Fluid Mixing and Related Nonlinear Phenomena

小行星9704301 这是一个更新的项目，将扩大我们的非线性物理现象的理解，特别是那些涉及颗粒材料和流体，使用小规模的实验室实验，并涉及本科生。 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步显微成像相结合。 这些改进将使粘滑运动的开始、前兆和向连续滑动的过渡得以详细研究。 一个目标是比较和对比颗粒摩擦与固体-固体摩擦。 第二个重点将是流体混合现象的研究，其中被动杂质是由流动混合。 这些实验将包括随机细胞流中的混沌平流和粒状介质中的运输的调查。 最后，继续对非线性波的图案形成和动力学进行实验，将探索具有多个空间周期性的六边形超晶格图案等现象。 这是一个更新的项目，它将扩展我们对非线性物理现象的理解，这些现象可能导致复杂或不可预测的行为。 该项目将特别关注颗粒或微粒材料和流体，使用小规模的实验室实验。 本科生的研究培训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与地震有关的方面具有潜在的重要性，尽管这些研究旨在获得基本的理解。 精细的力测量将与光学成像相结合，以了解突然滑动事件的发生，以及在重大事件之前发生的局部前兆。 研究的第二个领域将涉及流体混合现象，其中被动杂质被流体流运输或混合，该流体流可能包含多孔介质，例如沙子。 这类研究可能与杂质在土壤中的迁移有关。 ***

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. ***