Segregation and Spatio-Temporal Dynamics of Granular Shear Flows

颗粒剪切流的分离和时空动力学

• 批准号: 0434279
• 负责人: Benjamin Glasser
• 金额: --
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-15 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0434279&HistoricalAwards=false
• 关键词: Segregation; Spatio; Temporal; Dynamics; Granular

ABSTRACT - 0434279 Particulate processing operations in a wide variety of industries are often poorly understood compared to their fluid processing counterparts. Product quality and consistency is frequently threatened by problems such as non-uniform flow and segregation of constituent components, the latter being especially significant in pharmaceutical manufacture in which maintenance of a homogenous particle mixture is critical. Traditionally, heuristic rules-of-thumb have been used to limit these problems, but these have not reliably predicted flow instabilities and prevented segregation from occurring during scale-up or commissioning. A more desirable approach, from either a quality control, commercial, or regulatory perspective, is the ability to quantitatively predict flow inhomogeneities and segregation rates from fundamental principles, material properties and small-scale laboratory tests, and then to engineer processes accordingly to limit detrimental effects on performance and product uniformity. While there is a growing theoretical basis for granular flow, this has not yet been applied widely to non-uniform or unsteady flows which are typical of industrial situations. Fundamentally, segregation stems from variations in velocity and flow properties, such asgranular temperature, between adjacent regions of a system, preferentially driving particles of a certain type to particular locations. Thus, an initial aim is to numerically and experimentally characterize the flow instabilities and coherent structures occurring spontaneously during Couette and Taylor-Couette flows. Couette and Taylor-Couette flows are perhaps the simplest model geometries encompassing both shear and physical boundary interactions, essential ingredients of practical flows. Particle dynamic simulation techniques will be used to model particle properties and resulting flows will be characterized using Fourier methods and compared to results from kinetic theory. Experimental flows will be examined using Xray tomography, Particle Image Velocimetry (PIV), stream sampling, and image analysis techniques. The subsequent role of instabilities as triggers for segregation will then be investigated, culminating in calculations of segregation flux for a given particle species. Computational and physical experiments will be used to characterize mixing-segregation transitions in terms of relevant dimensionless groups. Underlying instabilities and spontaneous inhomogeneity will be examined in archetypal 2D and 3D Couette and Taylor-Couette flows, utilizing analogies with fluid flows where possible. Mechanisms of particle segregation triggered by the inhomogeneities will be characterized, for high-shear flows typical of mixing or transport operations. A parametric sensitivity analysis will be performed to quantify the role of particle size distribution, density variations, surface properties and particle aspect ratio. Initial work will consider spherical particles with work in latter years allowing for non-spherical particles. Particle shape is rarely considered in fundamental flow and segregation studies, but non-spherical particles predominate in industry and are known to strongly influence flow and segregation. In particular, acicular needle-like morphologies are common in pharmaceutical crystals and these will be studied experimentally and modeled in the simulations. The research initiatives in this proposal will be integrated with educational and outreach initiatives including graduate, undergraduate and high school research training in particle technology. Training in particle technology has been recognized as an area of national need but has traditionally been neglected in the US. A large proportion of the products manufactured within the US are in particulate form or involve significant particle technology. In fact, it has been argued that the handling and manufacture of particulates is at least as important as that of liquids and gases. But the majority of graduating engineers in the U.S. receive little education in this field. As part of this proposal, the PI will continue to advance particle technology into the curriculum at Rutgers. High school students will be given the opportunity for research experience through the Governor's School of Engineering, which attracts New Jersey high school students to Rutgers for a high school-university exchange program. Finally, the PI will continue to target the recruitment of women and minorities.

摘要- 0434279与流体处理对应物相比，对各种工业中的颗粒处理操作通常了解甚少。产品质量和一致性经常受到诸如不均匀流动和组成成分分离的问题的威胁，后者在药物制造中尤其重要，其中保持均匀的颗粒混合物是至关重要的。 传统上，启发式经验法则已被用来限制这些问题，但这些并没有可靠地预测流动不稳定性，并防止隔离发生在放大或调试。从质量控制、商业或监管的角度来看，一种更理想的方法是能够从基本原理、材料特性和小规模实验室测试中定量预测流动不均匀性和分离率，然后相应地设计工艺以限制对性能和产品均匀性的不利影响。虽然颗粒流的理论基础越来越多，但还没有广泛应用于工业情况下典型的非均匀或非定常流。 从根本上说，偏析源于速度和流动特性的变化，如颗粒温度，在系统的相邻区域之间，优先驱动某种类型的颗粒到特定位置。因此，最初的目标是数值和实验表征的流动不稳定性和相干结构发生在库埃特和泰勒库埃特流自发。库埃特流和泰勒-库埃特流可能是最简单的模型几何形状，包括剪切和物理边界相互作用，实际流动的基本成分。粒子动力学模拟技术将用于模拟粒子特性，并将使用傅立叶方法表征产生的流动，并与动力学理论的结果进行比较。实验流将使用X射线断层扫描，粒子图像测速（PIV），流采样和图像分析技术进行检查。随后的作用，作为触发器的不稳定性隔离，然后将进行调查，最终在一个给定的粒子种类的分离通量的计算。计算和物理实验将被用来表征相关的无量纲组的混合偏析过渡。 潜在的不稳定性和自发的不均匀性将在原型的2D和3D Couette和泰勒-Couette流，利用类比与流体流动在可能的情况下进行检查。由不均匀性引发的颗粒分离机制的特点是，典型的混合或运输操作的高剪切流。 将进行参数敏感性分析，以量化粒度分布、密度变化、表面性质和颗粒纵横比的作用。最初的工作将考虑球形颗粒，在以后几年的工作允许非球形颗粒。颗粒形状很少被认为是在基本的流动和偏析的研究，但非球形颗粒占主导地位，在工业和众所周知的强烈影响流动和偏析。 特别是，针状针状形态在药物晶体中很常见，这些将在模拟中进行实验研究和建模。本提案中的研究举措将与教育和推广举措相结合，包括粒子技术的研究生、本科生和高中研究培训。粒子技术的培训已被公认为国家需要的一个领域，但在美国传统上被忽视。 在美国生产的大部分产品是颗粒形式或涉及重要的颗粒技术。 事实上，有人认为，微粒的处理和制造至少与液体和气体的处理和制造同样重要。 但美国大多数毕业的工程师几乎没有接受过这方面的教育。作为这项提议的一部分，PI将继续推进粒子技术进入罗格斯大学的课程。高中生将有机会通过州长工程学院获得研究经验，该学院吸引新泽西高中生到罗格斯大学参加高中-大学交流项目。 最后，PI将继续针对妇女和少数民族的招聘。