基于几何光学的图像矫正法在圆管 PIV实验中的应用研究

粒子图像速度技术被广泛用于流体流动测量,介质折射率差异使光在圆管壁面发生偏折,导致图像失真,直接影响速度 测量精度。 本文建立了光学折射的物理模型,得到圆形管道中物点和图像点之间的函数关系进而得到矫正后图像的像素坐标, 使用双线性插值算法得到像素灰度值重建出矫正后的粒子图像,最后根据多重网格迭代算法计算管内速度场。 分别对流体进 行管内静态流体与管内层流速度场测量实验,对比了光学矫正箱法、线性矫正以及基于光学模型的畸变矫正方法误差。 结果表 明,本文提出的基于几何光学的图像矫正方法精度优于光学矫正箱法和线性矫正方法,并通过静态与流动实验充分验证了所建 立几何光学模型的准确性和有效性。

Application of image correction method in PIV velocity measurement of round pipes

Particle image velocimetry (PIV) technology is widely used in fluid flow measurement. The refractive index difference of the medium causes the light to deflect on the wall of the tube, which may result in image distortion and directly affect the accuracy of velocity measurement. In this article, the physical model of optical refraction is established, and the functional relationship between the object point and the image point in the circular pipe is achieved. Then, the pixel coordinates of the corrected image are obtained. The bilinear interpolation algorithm is used to obtain the pixel gray value to reconstruct the corrected particle image. Finally, the velocity field in the tube is calculated according to the multi-grid iterative algorithm. The static fluid grid image deviation and laminar flow velocity field measurement experiments are carried out respectively. The errors of optical correction box method, linear correction method and distortion correction method based on optical model were compared. The results show that the accuracy of the proposed image correction method based on geometric optics is better than those of the optical correction box method and the linear correction method. The accuracy and effectiveness of the established geometric optics model are fully evaluated by static and flow experiments.