Collaborative Research: Flow Instabilities in Gas-solid Flows

合作研究：气固流中的流动不稳定性

• 批准号: 1236157
• 负责人: Christine Hrenya
• 金额: $ 20.19万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1236157&HistoricalAwards=false
• 关键词: Collaborative; Research; Flow; Instabilities; Gas

1236157/1236490PI: Hrenya/YinGas-solid flows are ubiquitous in both nature (landslides, avalanches, planetary rings, etc.) and industry (pharmaceuticals, food products, chemical and petroleum industries). High-velocity gas-solids flows that are found in a wide range of applications (circulating fluidized beds, pneumatic transport lines, sand flow modeling, erosion prevention, planetary rings, etc.), in particular, often develop instabilities that are referred to as ?clusters?, which are known to have a large impact on system performance. Accurate prediction of onset and evolution of the clusters is critical to the design, scale-up, and optimization of related systems. It is shown that inelastic inter-particle collisions and gas-solid drag can both independently lead to instabilities; in real systems, however, they always cooperate and their relative importance has not been examined. The objective of this research is twofold: (i) to elucidate the relative importance of the various origins of the instabilities in high-velocity, gas-solid flows, and (ii) to critically assess the ability of a new kinetic-theory (continuum) model to predict the quantitative nature of such instabilities. This research will begin with a simplistic, time-dependent cooling system where kinetic energy input is absent, and then move to more complex and practically relevant fluidization systems with and without solid boundaries to investigate time-independent statistics. Four different computational methods will be used. Lattice Boltzmann simulations that solve the detailed flow around particles will be used to provide first-principle-based data sets needed to assess the relative importance of collisions and gas phase effects as well as cluster formation and evolution. On the continuum level, linear stability analyses based on two-fluid kinetic theories will first be used to predict the stability boundary; Euler-Lagrangian method where only gas phase is treated as a continuum and particles are discrete, and Euler-Euler models where both gas and particle phases are treated as continua, will then be used to simulate the evolution of the clusters. These results will be compared to the lattice Boltzmann data for a critical assessment of the predicative ability of the various continuum models. This research will generate first-principle-based simulation data on cluster formation and evolution for high-velocity gas-solid flows, and these data will be used to establish an accurate theory able to predict both onset and evolution of the clustering instability on the continuum level.The simultaneous flow of gas and solid particles occurs in windstorms, landslides, reactors used for energy production, and mixing units used by the pharmaceutical industry, to mention just a few. The complex physical interactions occurring in these systems make them difficult to predict from past experiments alone. In this project, mathematical models with no fitting parameters will be developed and used to predict flow phenomenon unique to these systems. The availability of such a modeling tool is expected to reduce to improved design of reactors in shorter turn-around times and at smaller costs than is currently possible. The model will be made available to researchers worldwide via an existing open-source code, and thus is expected to find future use in numerous sectors, including pharmaceuticals, chemical process industries, energy production, geology, and astrophysics.

1236157/1236490PI：Hrenya/Yin气固流在自然界（山体滑坡、雪崩、行星环等）和工业（制药、食品、化学和石油工业）中普遍存在。特别是在广泛的应用（循环流化床、气动输送线、砂流建模、侵蚀防护、行星环等）中发现的高速气固流，通常会产生不稳定性，称为“集群”，已知对系统性能有很大影响。 准确预测簇的发生和演化对于相关系统的设计、放大和优化至关重要。结果表明，非弹性粒子间碰撞和气固阻力都可以独立地导致不稳定性；然而，在实际系统中，它们总是合作，并且它们的相对重要性尚未得到检验。这项研究的目标有两个：（i）阐明高速气固流中不稳定性的各种起源的相对重要性，以及（ii）批判性地评估新的动力学理论（连续体）的能力）模型来预测这种不稳定性的定量性质。这项研究将从一个简单的、不存在动能输入的、与时间相关的冷却系统开始，然后转向更复杂、与实际相关的、有或没有固体边界的流化系统，以研究与时间无关的统计数据。将使用四种不同的计算方法。解决粒子周围详细流动的格子玻尔兹曼模拟将用于提供评估碰撞和气相效应以及团簇形成和演化的相对重要性所需的基于第一原理的数据集。在连续体层面，首先采用基于二流体动力学理论的线性稳定性分析来预测稳定性边界；仅气相被视为连续体而颗粒是离散的欧拉-拉格朗日方法，以及气相和颗粒相均被视为连续体的欧拉-欧拉模型将用于模拟团簇的演化。这些结果将与格子玻尔兹曼数据进行比较，以对各种连续介质模型的预测能力进行关键评估。这项研究将生成基于第一原理的高速气固流团簇形成和演化的模拟数据，这些数据将用于建立能够预测连续体上团簇不稳定性的发生和演化的准确理论气体和固体颗粒的同时流动发生在风暴、山体滑坡、用于能源生产的反应器以及制药行业使用的混合装置等中。 这些系统中发生的复杂物理相互作用使得它们很难仅从过去的实验中进行预测。 在该项目中，将开发没有拟合参数的数学模型，并用于预测这些系统特有的流动现象。 这种建模工具的可用性预计将在比目前可能的情况下以更短的周转时间和更低的成本来改进反应堆设计。 该模型将通过现有的开源代码提供给世界各地的研究人员，因此预计未来将在许多领域得到应用，包括制药、化学加工工业、能源生产、地质学和天体物理学。