Probing Multiscale Complex Multiphase Flows with Positrons for Engineering and Biomedical Applications

现代工程面临的一个重要挑战是对处于众多工业和生理过程核心的多尺度复杂颗粒-液体流动进行建模。依赖这种流动的行业包括食品、化学品、消费品、制药、石油、采矿、河流工程、建筑、发电、生物技术和医药。尽管有如此广泛的应用领域，但由于缺乏对所涉及的复杂、多尺度现象的基本了解，工业实践和流程以及临床实践既不高效也不优化。流动可能是湍流或粘性的，载体流体可能表现出复杂的非牛顿流变性。颗粒具有不同的形状、大小、密度、体积和表面属性。理解多尺度颗粒-液体流动并可靠地预测它们的能力将为英国带来巨大的经济、科学和社会效益。到目前为止，我们对这种流动的基本认识受到了巨大实际困难的限制，难以对这种流动进行成像和测量其当地性质。实际感兴趣的混合物通常是浓缩的和不透明的，因此不可能进行光流可视化。我们建议使用正电子发射粒子跟踪(PEPT)技术来克服这个问题，该技术依赖于穿透不透明材料的辐射。我们将通过非凡的实验和理论努力，在工程和生理学中推进多尺度颗粒-液体流动的基本物理，使我们对这些流动进行成像、建模、分析和预测的能力发生重大变化。我们将开发：(I)用于工程和生理流动的独特的变革性拉格朗日PEPT诊断方法；以及(Ii)用于分析我们的测量发现的现象的创新拉格朗日理论。发明PEPT技术的伯明翰大学正电子成像中心在使用发射正电子的放射性示踪剂研究工程过程方面是世界上独一无二的。在PEPT中，单个放射性标记粒子被用作流动跟踪器，并通过正电子检测进行跟踪。因此，多相颗粒-液体流动中的每一组分都可以被标记并观察其行为。与主要的光学激光技术(如LDV、PIV)相比，PEPT具有巨大而独特的优势，它可以成像不透明的流体，以及不透明的设备和人体内的流体。为了最大限度地利用这一点并快速成像水体系中复杂的多相和多尺度流动，提高跟踪灵敏度和精度，必须开发专用的新放射性示踪剂和同时跟踪多个示踪剂，并且必须设计新的理论框架来分析和解释数据。通过实现这一点，我们将能够以前所未有的细节和分辨率研究多尺度复杂的颗粒-液体流动，并在迄今为止任何可用的技术都无法达到的状态和构型中进行研究。由于PEPT在工程和医学中的应用范围非常广泛，因此带来的好处将是深远的。这一多学科计划利用伯明翰(化学工程、物理)、爱丁堡(应用数学)和伦敦国王学院(PET化学、生物医学工程)等世界领先中心之间的协同作用，开发独特的PEPT诊断工具，并从实验和理论上研究只有这些工具才能解决的突出的多尺度多相流问题。该计划的进展包括：设计用于对微尺度流动进行成像的新型微型PEPT设备，以及在小动物身上验证的可移植到人类的新型医用PEPT。研究人员的综合优势和随之而来的广泛的工业合作将确保该计划导致复杂的多相流研究的范式转变。

A vital challenge for modern engineering is the modelling of the multiscale complex particle-liquid flows at the heart of numerous industrial and physiological processes. Industries dependent on such flows include food, chemicals, consumer goods, pharmaceuticals, oil, mining, river engineering, construction, power generation, biotechnology and medicine. Despite this large range of application areas, industrial practice and processes and clinical practice are neither efficient nor optimal because of a lack of fundamental understanding of the complex, multiscale phenomena involved. Flows may be turbulent or viscous and the carrier fluid may exhibit complex non-Newtonian rheology. Particles have various shapes, sizes, densities, bulk and surface properties. The ability to understand multiscale particle-liquid flows and predict them reliably would offer tremendous economic, scientific and societal benefits to the UK. Our fundamental understanding has so far been restricted by huge practical difficulties in imaging such flows and measuring their local properties. Mixtures of practical interest are often concentrated and opaque so that optical flow visualisation is impossible. We propose to overcome this problem using the technique of positron emission particle tracking (PEPT) which relies on radiation that penetrates opaque materials. We will advance the fundamental physics of multiscale particle-liquid flows in engineering and physiology through an exceptional experimental and theoretical effort, delivering a step change in our ability to image, model, analyse, and predict these flows. We will develop: (i) unique transformative Lagrangian PEPT diagnostic methodology for engineering and physiological flows; and (ii) innovative Lagrangian theories for the analysis of the phenomena uncovered by our measurements.The University of Birmingham Positron Imaging Centre, where the PEPT technique was invented, is unique in the world in its use of positron-emitting radioactive tracers to study engineering processes. In PEPT, a single radiolabelled particle is used as a flow follower and tracked through positron detection. Thus, each component in a multiphase particle-liquid flow can be labelled and its behaviour observed. Compared with leading optical laser techniques (e.g. LDV, PIV), PEPT has the enormous and unique advantage that it can image opaque fluids, and fluids inside opaque apparatus and the human body. To make the most of this and image fast, complex multiphase and multiscale flows in aqueous systems, improved tracking sensitivity and accuracy, dedicated new radiotracers and simultaneous tracking of multiple tracers must be developed, and new theoretical frameworks must be devised to analyse and interpret the data. By delivering this, we will enable multiscale complex particle-liquid flows to be studied with unprecedented detail and resolution in regimes and configurations hitherto inaccessible to any available technique. The benefits will be far-reaching since the range of applications of PEPT in engineering and medicine is extremely wide. This multidisciplinary Programme harnesses the synergy between world-leading centres at Birmingham (chemical engineering, physics), Edinburgh (applied maths) and King's College London (PET chemistry, biomedical engineering) to develop unique PEPT diagnostic tools, and to study experimentally and theoretically outstanding multiscale multiphase flow problems which can only be tackled by these tools. The advances of the Programme include: a novel microPEPT device designed to image microscale flows, and a novel medical PEPT validated in small animals for translation to humans. The investigators' combined strengths and the accompanying wide-ranging industrial collaborations, will ensure that this Programme leads to a paradigm-shift in complex multiphase flow research.