Multiscale plenoptic imaging and direct computation of turbulent channel flows laden with finite-size solid particles

在各种工业、生物和环境过程中都存在含有颗粒的湍流。对这些流动的分析具有挑战性，因为悬浮颗粒与周围流体之间的相互作用不仅会影响颗粒的动力学，还会影响整体流动的特性。该奖项将支持计算和实验工具的发展，以更好地理解颗粒尺度上的颗粒-流体相互作用如何影响大尺度湍流中的输运。在明渠湍流中，将建立一套记录载重颗粒流体三维速度场的成像系统。实验结果将与相同流动的数值模拟进行比较，以验证模拟方法，并为颗粒动力学和流动之间的关系提供额外的见解。研究小组将在一个新的短期课程中整合该项目的成果，该课程将计算流体动力学与计算成像和计算机视觉的新技术相结合。将为参加特拉华大学高中暑期研究项目的高中生和教师开发一个说明这些方法的教学模块。本文将构建一个全光学粒子跟踪测速系统，该系统可以在微观和宏观尺度上测量三维湍流、粒子负载流中的三分量速度场。这种测速方法使用全光学相机，可以同时从不同的视点和角度记录一组粒子的许多图像。然后，利用计算机视觉算法精确地恢复粒子在三维空间中的瞬时位置，并利用该位置求出速度场；此外，本项目中的粒子跟踪系统将被设计用于捕获单个粒子的旋转速度。同时，基于介观晶格玻尔兹曼方法的高度可扩展的粒子分辨模拟工具将被应用于解决所有尺度的三维运动。模拟结果将与所有尺度的实验数据进行比较。在粒子尺度上，这些数据包括粒子的轨迹、速度、加速度和角速度，粒子-壁面和粒子-自由表面的相互作用，以及固体粒子表面附近的局部流动统计。在系统尺度上，这些工具将用于研究有限尺寸固体颗粒存在下的湍流调制、流动阻力和流动转变。

CBET - 1706130PI: Wang, Lian-PingTurbulent flows that contain particles occur in a variety of industrial, biological, and environmental processes. The analysis of these flows is challenging, because interactions between the suspended particles and the surrounding fluid not only affect dynamics of the particles, but also influence characteristics of the overall flow. This award will support development of computational and experimental tools to better understand how particle-fluid interactions at the particle scale influence transport in turbulent flow at large scales. An imaging system will be constructed to record three-dimensional velocity fields of particle-laden fluids in turbulent open-channel flow. Experimental results will be compared with numerical simulations of the identical flow to validate the simulation methods and provide additional insight into relationships between particle dynamics and flow. The research team will incorporate results from the project in a new short course that will combine computational fluid dynamics with new techniques in computational imaging and computer vision. An instructional module illustrating these methods will be developed for high school students and teachers participating in the High School Summer Research program at the University of Delaware.A plenoptic particle tracking velocimetry system will be constructed that can measure the three-component velocity fields in three-dimensional, turbulent, particle-laden flows at both micro- and macro-scales. This velocimetry method uses a plenoptic camera that can record many images of a collection of particles from different viewpoints and angles at the same time. Then, computer vision algorithms are applied to recover accurately the instantaneous positions of the particles in three dimensions, which can be used to find the velocity fields. In addition, the particle tracking system in this project will be designed to capture the rotational velocity of individual particles. In parallel, a highly scalable particle-resolved simulation tool based on the mesoscopic lattice Boltzmann approach will be applied to resolve the three-dimensional motion at all scales. Results from the simulations will be compared with experimental data at all scales. At the particle scale, these data include trajectories, velocities, accelerations, and angular velocities of particles, particle-wall and particle-free surface interactions, as well as local flow statistics near the surface of a solid particle. At the system scale, the tools will be used to study turbulence modulation, flow drag, and flow transition in the presence of the finite-size solid particles.