非定常三维复杂流动的单相机层析PIV测量系统研究

As the most advanced volumetric particle image velocimetry (PIV), tomographic PIV overcomes the issue of low tracer density in volumetric PIV measurements because of its multiplicative algebraic reconstruction technique (MART). Tomographic PIV has been widely used in experimental measurements due to its good performance on spatial resolution comparing to other volumetric PIV techniques. However, the costliness and complicity of a tomographic PIV system with multiple cameras slow down its expansion on application. For better applying tomographic PIV technique to measure complex and turbulent flows, this project aims to develop a single-camera tomographic PIV system. The system includes hardware and software, which only uses one camera to achieve a three-dimensional three-component (3D3C) velocity measurement with equivalent accuracy of a general tomographic PIV system. Besides the simplification of the setup, the data processing algorithms will be optimized as well as applying parallel processing and acceleration using the technique of graphics processing unit (GPU) in the software. Meanwhile, data analysis methods on a 3D3C experimental velocity field will be studied, such as three-dimensional mode-decomposition techniques and vortex identification algorithms. Eventually, the new system will be tested on a measurement of turbulent boundary layer flow using single-camera tomographic PIV system to verify the reliability and practicability of the new developed measurement system.

层析PIV技术作为最新的体PIV测量技术，通过MART算法有效解决了PIV体测量中示踪粒子浓度不能太高的问题，使测量的空间分辨率大大提高，并开始被应用于实验测量。然而复杂的多相机实验平台使得层析PIV测量成本高昂且操作困难，这些都限制它的应用推广。为了使层析PIV具有更广的适用性，能更好应用于非定常复杂三维流动的测量，项目将研制一种单相机层析PIV测量的系统。该系统包括实验平台和数据处理软件，在保证传统层析PIV测量精度的前提下，仅利用一台相机实现时间解析的3D3C速度场测量。在简化实验平台的同时，系统将采用更为优化的层析PIV算法，数据处理实现并行计算和GPU硬件加速。同时，探索三维模态分解和三维旋涡辨识等针对3D3C实验数据的流场诊断技术。最终，将利用单相机层析PIV系统实现湍流边界层流动的多尺度测量，以验证单相机层析PIV系统的可靠性和实用性。

由于层析PIV系统硬件复杂、成本高昂，本项目旨在保证精度的前提下,研制出一种仅用单台相机实现层析测量的简化的层析PIV测量系统。项目立项计划书中设定的研究目标为两个方面：一是研发具有自主知识产权的单相机层析PIV 测量系统；二是将该项技术应用于湍流边界层流动的测量。项目按计划①完成了单相机层析粒子图像测速（PIV）实验平台的研制，对单相机层析PIV成像系统进行了参数影响规律的研究，提出了最优布置方案：单相机四复眼三维PIV测量系统。相较于之前的三复眼系统，其可重构区域面积提升了约60%左右。②提出了基于单相机层析PIV的数据处理方法，提高了体标定和粒子重构等方面的效率。③在数据处理加速方面，在数据处理软件中引入了并行计算和GPU加速技术，极大地提高了数据处理的效率。④完成了系统数据处理软件各模块的验证与集成，形成了完整的单相机层析PIV数据处理软件。⑤该技术已经应用涡环三维演化、边界层内半球绕流结构、湍流边界层结构等的研究，发现了一些新的现象。项目超额完成了研究计划规定的任务，通过实验验证，单相机层析PIV系统的性能指标全部达到预定设计指标，关键技术指标处于国际领先水平。本项目所研究出的单相机层析PIV测量仪器的精确度高，可靠性强，且简单易用成本低廉，可以为层析PIV测量技术的普及和发展提供助力。