Applying numerical modeling to experimental data for improved optical diagnostics of fluid flows

在学术和工业应用中，对流体运动的实验研究现在由数字技术主导。摄像机被用来拍摄被播种到流动中的示踪剂颗粒的图像，以跟踪它们的运动，从而推断流体的运动。这项技术在过去的30年里得到了发展，现在它甚至可以与最详细的数值模拟兼容。重要的是，这些实验技术包含了流动问题的所有物理原理。因此，它们被用作数值方法的直接验证，以及学术界和工业界调查各种流动的工具。现在，基于粒子图像测速(PIV)和粒子跟踪测速(PTV)的这些技术大家族已经存在。这些多摄像机系统在设置、数据收集和处理到描述性速度场方面面临许多挑战。*一种从单个摄像机采集三维(3D)粒子位置图像的新方法是基于收集摄像机所看到的整个光场。这种相机被称为全光成像，它有一个微透镜阵列，可以从小角度透视观察粒子的位置。这种类型的成像系统只使用一个摄像头，在FLOW系统中安装和设置起来非常容易，特别是在观看权限有限的情况下。它还首次实现了对微观尺度上的三维流动的真实测量，例如多孔介质中的流动和微尺度的生物流动。该项目将继续开发用于实验的这类相机系统，开发基于PTV和粒子运动数值模型的通用校准程序、数据收集和处理以及先进的方法，以提供高质量的流动测量。*对于任何粒子成像速度测量技术，都需要一种适当的方法来确定导出的速度矢量中的不确定度。到目前为止，由于实验装置和收集的数据的计算处理的复杂相互作用，还没有通用的方法来确定PIV或PTV测量的不确定度。这是一个重大的根本性问题，对整个实验热流体社区产生了强烈的影响，无论是在学术界还是工业界。这个项目的一个重要部分将是开发一种通用的方法来确定所有这些类型的粒子图像速度测量系统的不确定度。*这个项目将培训HQP在光学仪器和流体力学领域发展新的知识和科学。在这些技术被单一化的学术界和工业界都将感受到影响。

Experimental research into the motion of fluid in academic and industrial applications is now dominated by digital techniques. Cameras are used to take images of tracer particles seeded into the flow to track their movement, inferring the motion of the fluid. This technology has been developed over the last 30 years to a point where it is now compatible with even the most detailed numerical simulations. Importantly, these experimental techniques include all of the physics of the flow problem. They are therefore used as direct validation of the numerical approaches as well as a tool in academia and industry to investigate a wide variety of flows. A large family of these techniques now exist based on particle image velocimetry (PIV) and particle tracking velocimetry (PTV). These multi-camera systems have many challenges in the setup, the collection of data and the processing through to descriptive velocity fields.****A new approach to collect images of particle locations over three dimensions (3D) from a single camera is based on collecting the entire light field seen by the camera. Termed plenoptic imaging, the camera has a microlens array that allows small angle perspective viewing of particle locations. This type of imaging system, using only a single camera, promises to be significantly easier to install and setup in a flow system, especially where viewing access is limited. It also allows, for the first time, realistic measurement of three-dimensional flows at the microscale such as the flow in porous media and microscale biological flows. This project will continue to develop this type of camera system for experimental use by developing a general calibration procedure, data collection and processing and advanced approaches based on PTV and numerical models of particle motion to provide high-quality flow measurement.****With any particle imaging velocimetry technique, an appropriate methodology is needed to determine the uncertainty in the derived velocity vector. As yet, no generalised method for determining the uncertainty in a PIV or PTV measurement is available due to the complex interaction of the experimental setup and the computational processing of the data collected. This is a significant fundamental problem that has a strong impact across the experimental thermo-fluid community, both in academia and industry. A significant part of this project will be the development of a generalised methodology for determining the uncertainty in all of these types of particle image velocity measurement systems.****This project will train HQP in the areas of optical instrumentation and fluid mechanics developing new knowledge and science. Impact will be felt in both academia and industry where these techniques are unitized.******