单台彩色相机4D-PIV的三色掩膜成像机理及三维重构研究

叶轮机械作为“两机专项”重大装备的能量转换部件，精细气动设计严重依赖于对流道内复杂流动的准确诊断与有效控制，但现有三维PIV技术在受限空间复杂流场的高频响三维测量方面仍存在不足。为此，结合彩色PIV能够提供更多信息的优势，采用三色掩膜将颜色信息与视角信息结合，提出一种单台彩色相机三色掩膜成像思想，实现流场4D-PIV（时间分辨、三维空间分辨）测量。构建粒子到三色掩膜彩色图像的成像模型，分析成像系统主要参数对三维空间分辨率的影响，揭示三色掩膜成像机理；研究完整画幅全分辨率三视角图像提取，三维体标定及标定结果偏差自校准方法；结合示踪粒子均匀稀疏分布特性，研究融合传统重构算法及深度学习的高精度、高效率粒子三维重构；分析成像系统硬件主要参数、三维重构软件参数、流场关键指标对重构性能的影响。为受限空间复杂流场的高频响三维测量提供一种全新的解决方案，同时为其他流场的三维测试提供一种思路和手段。

Turbomachinery transfers energy between fluids and rotor blades. Its efficacy can be increased by improving the aerodynamic aspect of the design, which requires accurate flow diagnostics and effective control of the complex turbulent flow in the flow channel. Nonetheless, experimental measurements of the turbulent flow are highly challenging because the flow is highly three-dimensional, has wide turbulence spectra range and is confined in an enclosed space. To address these challenges and advance turbomachinery designs, a novel 4D-PIV technique which offers time-resolved, three-dimensional and three-component velocity measurements is proposed. The 4D-PIV leverages upon a single color camera and a trichromatic mask to extract perspective information of seeded particles in the flow field. This can be achieved by constructing a particle-to-color image mapping model, and then analyzing the influence of the main parameters of the trichromatic imaging system on the three-dimensional spatial resolution to determine the imaging mechanism of the trichromatic mask. The method to extract three full-frame full-resolution perspective images will be explored, and 3D calibration and calibration result deviation self-calibration methods will be developed. A highly precise and efficient particle reconstruction algorithm which combines traditional reconstruction algorithms and deep learning will be studied to improve the reconstruction of uniform and sparsely distributed seeding particles. The effects of major hardware parameters, reconstruction software parameters and key indicators of the flow field on the reconstruction performance of the imaging system will be analyzed. The proposed research project presents a new solution that offers high frequency response and three-dimensional velocity measurements of complex turbulent flows in confined spaces. The novelty of the project is expected to introduce fresh perspectives and methods for three-dimensional velocity measurements, which will impact various fields of research in experimental fluid mechanics.