基于光流算法的粒子图像测速技术研究和验证

On the PIV Technology and Validation Based on Optical Flow Algorithm

光流测量技术作为一种新的空气动力学实验技术,以其像素级分辨率的矢量场测量优势获得广泛的应用。光流测量技术使用光流约束方程,配合平滑限定条件,可以进行速度场测量,获得高分辨率的全局矢量场。本文首先通过研究积分最小化光流测速理论和算法,采用C++编写光流速度测量程序;然后通过三种典型的人工位移图像对光流计算程序进行了验证,并将结果和标准位移分布进行比对分析,以指导如何在实际应用中获得高精度光流速度场;最后进行小型风洞后向台阶实验,利用高速相机拍摄示踪粒子图像,使用光流计算程序获得速度矢量场,同采用互相关算法的粒子图像测速计算结果相比较,体现出光流计算方法像素级分辨率的矢量场测量优势。

Optical flow measurement technology,as a new aerodynamic experimental method,has been widely used in vector field measurement due to its advantage of pixel scale resolution.By means of optical flow scalar constraint equation,combining with smooth limit condition,optical flow experimental technique can measure global velocity vector field with high space resolution.Firstly,integral minimization optical flow velocimetry theory and algorithm were studied and programmed by C＋＋;then,in order to verify the optical flow algorithm accuracy,three kinds of typical grayscale image shifted from artificial displacement were used for processing by the optical flow algorithm;finally,the obtained results were compared with the distribution of standard displacement to guide how to obtain optical flow velocity field in practical application.A backward step experiment in small wind tunnel was carried out.High speed camera was used to shoot tracer particle image;the velocity vector field was calculated by optical flow algorithm.Calculated results from optical flow algorithm were compared with result calculated by PIV correlation algorithm.Results show that optical flow experimental technique presents the advantages of pixel scale resolution.