Effects of particle shape and fluid shear on the kinematics and mass transfer of large particles in turbulent flow

PI：Variano，EvanProposal Number：1604026拟议研究的目标是从实验和理论上探索高浓度颗粒的湍流物理。该建议侧重于复杂的，同时也是工程应用中常见的情况，即由于漂移和惯性的共同作用，非球形颗粒在流场中运动。这种流动在化学加工工业(例如，流态化催化反应器、气力输送)和环境中很突出。大到超过斯托克斯限的颗粒将在湍流中测量。总体目标是在惯性不可忽略的情况下更好地了解颗粒运动，而具体目标是了解颗粒形状如何影响对流体剪切的响应。实验室测量将揭示粒子的加速、旋转和单个粒子与周围流体之间的质量转移。一组粒子将用透明的、折射率匹配的材料和内部示踪剂制造，从而能够在三维中对其旋转和平移进行光学测量。第二组颗粒将由一种新型的中性浮力二氧化硅-蔗糖玻璃制成，这种玻璃被设计为缓慢溶解，从而能够测量颗粒和流体之间的质量交换。将研究的形状是圆柱体和圆锥体；将添加类似尾部和尾翼的额外形状特征，以帮助评估颗粒与局部相干结构对齐在湍流中的作用。超出斯托克斯极限的延伸可以揭示新的现象，因为惯性增加了粒子与局部剪切相互作用的复杂性。拟议中的项目将探索惯性机制，为大粒子如何与湍流相互作用提供观测证据。数值方法不能很容易地模拟感兴趣的运动，因此提出的实验室技术被开发来快速探索大范围的形状。本文所述类型的粒子出现在许多科学和工程领域，拟议的工作将通过提供相关物理的第一个详细描述来推进这些领域的研究。一个工程机会的例子是小型机器人车辆的设计。本文的结果将使导航和传感策略的设计成为可能，并确定车辆形状将如何影响这些策略。生物学和生物力学领域的相关机会包括改进对动物在动荡环境中的行为的描述，特别是对平衡游泳和漂流的中型水生生物。对教育的影响将包括制作一系列将在网上分发的视频。这些视频将提供颗粒在湍流和层流中跨尺寸、形状和浮力区域的统一运动演示，秉承经典的国家流体力学委员会电影的精神。

PI: Variano, EvanProposal Number: 1604026The goal of the proposed research is to experimentally and theoretically explore the physics of turbulent flows with high concentration of particles. The proposal focuses on the complex, and at the same time common in engineering applications, case of non-spherical particles that move on the flow field because of the combined effectws of drift and of inertia. Such flows are prominent in the chemical process industry (e.g., fluidized bed catalytic reactors, pneumatic transport) and in the environment. Particles large enough to exceed the Stokesian limit will be measured in turbulent flow. The general objective is to better understand particle motion for cases in which inertia is non-negligible, and the specific objective is to understand how particle shape influences response to fluid shear. Laboratory measurements will reveal particle acceleration, rotation, and mass transfer between individual particles and the surrounding fluid. One group of particles will be manufactured with transparent, refractive-index-matched materials and internal tracers, thereby enabling optical measurements of their rotation and translation in three dimensions. A second group of particles will fabricated from a new type of neutrally-buoyant silica-sucrose glass that was designed to slowly dissolve, thereby enabling measurements of the mass exchange between particles and fluid. The shapes that will be studied are cylinders and cones; additional shape features resembling tails and fins will be added to help evaluate the role of particle alignment with local coherent structures in the turbulent flow. Extending beyond the Stokesian limit can reveal new phenomena because inertia adds complexity to the interaction of particles with local shear. The proposed project will explore the inertial regime, providing observational evidence of how large particles interact with turbulence. Numerical methods cannot easily simulate the motions of interest, and thus the proposed laboratory techniques were developed to rapidly explore a large range of shapes. Particles of the type examined herein appear in many areas of science and engineering, and the proposed work will advance study in these areas by providing the first detailed description of the relevant physics. An example engineering opportunity lies in the design of small-scale robotic vehicles. The results herein will enable the design of navigation and sensing strategies, and determine how vehicle shape would influence these strategies. Related opportunities in the fields of biology and biomechanics include an improved description of animal behavior in turbulent environments, especially for mid-size aquatic organisms that balance swimming with drifting. Educational impacts will include the production of a series of videos that will be distributed online. These videos will provide a unified demonstration of particle motion across size, shape, and buoyancy regimes in both turbulent and laminar flows, in the spirit of the classic National Committee for Fluid Mechanics films.