Transactions between Granular Flow and Solidification: Merging Multiphase Transport with Statistical Mechanics

摘要-0456420在过去的十年里，颗粒物理学经历了一次兴趣的复兴，导致了从孤立粒子到新的奇异现象。[Umbanhowar，1996]到至今无法解释的旅行隔离波[Choo，1997]。 这些和其他令人惊讶的行为继续以规律的速度被发现，这主要是因为我们无法提前预测颗粒实验的结果，而我们可以在分析上更成熟的流体动力学领域中预测结果。 在受限状态中，例如对于快速碰撞流，已经开发并证明了可靠的颗粒模型，但是很少存在捕获从固体状到流体状的多个状态的预测模型。 因此，在本提案中，我们寻求精确地关注类固体和类流体共存区域之间的界面，最终目标是建立一个经过实验验证的、定量的、跨越颗粒床凝固-流化界面的第一原理模型。 所提出的方法结合了详细的颗粒密度和流量数据的实验测量与现有的分析模型。 我们将集中我们的调查级联流在磁盘上：一个系统，以前没有被广泛研究，但揭示了丰富的各种状态与复杂的接口，我相信可以作为一个独特的和有用的测试平台的调查功能的兴趣。 除了表现出许多不同的图案状态，磁盘系统允许我们探测床的离心应力，这将提供独特的见解凝固和流化机制的反应。 目前还不可能在固体和流体共存的颗粒系统中进行普遍适用和实际有用的预测。 然而，这种状态描述了相当大的范围，甚至可以说是大多数工业和地球物理颗粒系统（见下文）。 所提出的工作将产生显着的改善，在定量表征的内部和表面状态的这种系统和预测建模能力。 这项工作将通过一个经过验证的连续模型的结合来实现这一目标，该模型允许同时精确模拟凝固和流化状态，并采用最佳的实验技术，包括高速视频和X射线成像的粒子图像测速。 我们将研究的实验配置是独特的，并允许颗粒流如何响应于施加的压缩应力和诱导剪切的变化进行评估。 计算模型已被证明可以正确地再现复杂的固体-流体在颗粒悬浮液中的转变，并将在这项工作中扩展到干颗粒。 这种方法将导致对复杂颗粒床内部状态的详细了解，在过渡颗粒流的流变学建模方面取得重大进展，并且可能在针对以前无法准确模拟的问题的预测建模能力方面取得重大改进。更广泛的影响人们不需要努力寻找这项研究的广泛影响。 在工业方面，影响是明确的：正如我们在提案介绍中所描述的，当涉及颗粒材料时，制造效率下降到60%[纳尔逊，1995]，并且以制药工业为例，由于无法科学地预测结果和可靠的生产过程中随之发生的故障，整个制造工厂和生产线经常完全关闭。颗粒流和混合系统的设计[USA，1994; Muzzio，2002]。 所提出的工作将提供的数据将是直接有益的工业系统的预测设计，从转鼓到溜槽，其中凝固和流化状态共存。在更远的地方，在地质系统中，所提出的工作可以直接应用于滑坡动力学，但即使在这个领域内，也有比人们想象的更广泛的影响。 例如，在火星水物理学中仍然存在一个未解决的悖论，其中同时存在强烈的地貌证据表明最近的液态表面水（例如蜿蜒的通道）和明确的证据表明表面温度和压力远远低于可以维持这种水的值[Christensen，2003; Malin，1999，2000]。 在这场争论中，有人提出，许多与液态水有关的地貌实际上可能是由干燥的风成作用产生的[Treiman，2003; Leovy，2003]。 然而，几乎没有基本的预测模型可以明确地证实或反驳这一建议[Shinbrot，2004 b]。 同样，在地球物理学中，长距离雪崩[Melosh，1996]和地震[Scott，1996]所耗散的能量已经被测量为令人困惑的小，我们所描述的工作也揭示了这些系统中的冻结流化颗粒相互作用。

ABSTRACT - 0456420Granular physics has undergone a renaissance of interest over the past decade, leading to new and exotic phenomena ranging from solitary oscillons. [Umbanhowar, 1996] to as yet unexplained traveling segregation waves [Choo, 1997]. These and other surprising behaviors continue to be discovered at a regular rate largely because we cannot predict outcomes in granular experiments in advance, as we can in the more analytically mature companion field of fluid dynamics. In restricted regimes, for example for rapid collisional flows, reliable granular models have been developed and proven, but few if any predictive models exist that capture multiple regimes ranging from the solid-like to the fluid-like. Therefore in this proposal, we seek to focus precisely on the interface between solid-like and fluid-like coexisting regions with the ultimate goal of producing an experimentally validated, quantitative, first principles model that spans the solidified-fluidized interface of granular beds. The proposed approach combines detailed experimental measurements of granular density and flow data with an existing analytic model. We will focus our investigations on cascading flow on a disk: a system that has not been extensively studied before, yet reveals a rich variety of states with complex interfaces that I believe can serve as a unique and useful testbed for the investigation of the features of interest. In addition to exhibiting numerous distinct patterned states, the disk system permits us to probe bed responses to centrifugal stress, which will provide unique insights into solidification and fluidization mechanisms. Intellectual Significance It is not currently possible to make generally applicable and practically useful predictions in granular systems where solid-like and fluid-like regions co-exist. Yet this state describes a considerable range arguably even a majority of industrial and geophysical granular systems (see below). The work proposed will generate significant improvements both in quantitative characterization of internal and surface states of such systems and in predictive modeling capabilities. The work will achieve this through the combination of a validated continuum model that permits the accurate simulation of solidified and fluidized regimes simultaneously with the best available experimental techniques including Particle Image Velocimetry of high speed video and X-ray Imaging. The experimental configuration that we will study is unique and permits the evaluation of how granular flow responds to changes in applied compressive stress and induced shear. The computational model has been demonstrated to correctly reproduce complex solid-fluid transitions in granular suspensions, and will be extended to dry grains in this work. This approach will lead to a detailed understanding of internal states within a complex granular bed, to significant advances in rheological modeling of transitional granular flows and, potentially, to a major improvement in predictive modeling capability to problems previously inaccessible to accurate simulation. Broader Implications One does not need to look hard to find broad implications of this research. On the industrial side, the implications are clearcut: as we describe in the proposal introduction, manufacturing efficiencies drop to 60% when granular materials are involved [Nelson, 1995], and taking the pharmaceutical industry as a case in point, entire manufacturing plants and product lines are not infrequently shut down entirely due an inability to scientifically predict outcomes and consequent failures in the reliable design of granular flow and mixing systems [USA, 1994; Muzzio, 2002]. The data that the proposed work will provide will be of direct benefit for the predictive design of industrial systems ranging from tumblers to chutes in which both solidified and fluidized states co-exist. Further afield, in geological systems the proposed work can be applied directly to landslide dynamics, but even within this field, there are broader implications than one might suspect. For example, there remains an unresolved paradox in Martian geophysics in which there is simultaneously strong geomorphological evidence for recent liquid surface water (e.g. sinuous channels) and definitive evidence that surface temperatures and pressures are far below values that could sustain this water [Christensen, 2003; Malin, 1999, 2000]. Into this controversy has been thrown the suggestion that many of the landforms associated with liquid water may in fact have been produced by dry Aeolian processes [Treiman, 2003; Leovy, 2003]. Yet there exists little in the way of fundamental predictive modeling that could definitively confirm or refute this suggestion [Shinbrot, 2004b]. Likewise, in terrestrial geophysics, the energy dissipated by long runout avalanches [Melosh, 1996] and by earthquakes [Scott, 1996] have been measured to be perplexingly small, and the work that we describe stands to shed light on frozen-fluidized granular interactions in these systems as well.