Rod Dynamics in Turbulence: Simultaneous 3D measurements of Anisotropic Particles and Velocity Fields

****技术摘要****在广泛的自然和工业情况下，湍流携带颗粒物质。因此，湍流悬浮液和气溶胶的动力学一直是一个活跃的研究领域。在描述球形粒子在湍流中的运动方面取得了重大进展；然而，人们对各向异性粒子的动力学知之甚少。各向异性粒子的旋转是由湍流的小尺度特性决定的，这些特性在大范围的流动中几乎是普遍的，因此各向异性粒子提供了一个丰富的系统，可以直接将实验与理论和模拟进行比较。这里提出的研究将提供第一个高分辨率的实验测量在湍流中棒状颗粒的三维动力学。然后，我们将这些测量扩展到各向异性物体，从杆到各向同性粒子到磁盘的宽高比。我们还将实施最近开发的测量系统，该系统将允许极高的播种密度，以便在测量抽油杆运动的同时测量流体的速度梯度。这将允许测量粒子沿着其轨迹所经历的拉伸，这是负责各向异性粒子优先排列的基本量。教育和研究培训是该项目的核心，该项目将支持本科生、研究生和博士后科学家的指导，并培训K-12物理科学教育工作者。****非技术摘要****在广泛的自然和工业情况下，湍流携带颗粒物质。例如，云是包含水滴和冰晶的湍流。造纸使用纤维的湍流悬浮。如果粒子是球体，有各种各样的工具可以用来测量它们的运动。但通常这些粒子不是球形的，非球形粒子的运动和旋转从未被测量过，因为它们是由湍流携带的。这个项目将开发实验工具来进行这些测量。粒子旋转是特别有趣的，因为它们的统计数据预计在所有湍流中都是相似的，并且可以将测量结果与湍流普遍特性的理论预测进行比较。这项工作旨在建立对实验室湍流中非球形粒子运动基本特征的清晰理解，这些基本特征可用于理解更复杂的应用，如冰云和造纸。教育和研究培训是该项目的核心，该项目将支持本科生、研究生和博士后科学家的指导，并培训K-12物理科学教育工作者。

****Technical Abstract****In a wide range of natural and industrial situations, turbulent flows carry particulate material. As such, the dynamics of turbulent suspensions and aerosols has been an active area of research. Significant progress has been made in characterizing the motion of spherical particles in turbulence; much less is known, however, about the dynamics of anisotropic particles. The rotation of anisotropic particles is determined by small scale properties of turbulence that are nearly universal across a wide range of flows, and so anisotropic particles provide a rich system where experiments can be directly compared with theory and simulations. The research proposed here will provide the first high-resolution experimental measurements of the 3D dynamics of rod shaped particles in turbulence. We will then extend these measurements to anisotropic objects across the full range of aspect ratios from rods to isotropic particles to disks. We will also implement a recently developed measurement system that will allow extremely high seeding densities necessary to measure the velocity gradients of the flow simultaneously with measurements of rod motion. This will allow measurement of the stretching experienced by the particle along its trajectory which is the fundamental quantity responsible for preferential alignment of anisotropic particles. Education and research training are central to this project, which will support the mentoring of undergraduates, graduate students, and a postdoctoral scientist, as well as training K-12 educators in physical science.****Non-Technical Abstract****In a wide range of natural and industrial situations, turbulent flows carry particulate material. For example, clouds are turbulent flows containing water droplets and ice crystals. Papermaking uses turbulent suspensions of fibers. If the particles are spheres, there are a variety of tools available for measuring their motion. But usually the particles are not spheres, and the movement and rotations of non-spherical particles have never before been measured as they are carried by a turbulent flow. This project will develop experimental tools to make these measurements. Particle rotations are of particular interest because their statistics are expected to be similar in all turbulent flows, and measurements can be compared with theoretical predictions for the universal properties of turbulence. This work seeks to establish a clear understanding of the fundamental characteristics of non-spherical particle motion in laboratory turbulent flows that can be used to understand more complex applications such as icy clouds and papermaking. Education and research training are central to this project, which will support the mentoring of undergraduates, graduate students, and a postdoctoral scientist, as well as training K-12 educators in physical science.