超空泡实验中的数字图像检测

Edge location and detection in supercavitation's digital imagery

在水洞实验中,高速摄像机以数十赫兹至数十千赫的速度记录空化过程的系列影像,是研究水中空化现象机理的有力工具。如何从众多的数字图像中准确获取空泡的外形、空泡波动周期等信息,同时克服背景干扰和光线在空气、水以及水洞观察窗面板中的折射效应,是进行超空泡非定常实验要解决的重要课题。文中应用现代数字图像分析理论,通过对图像的滤波、灰度拉伸、图像校准、边缘检测等操作,总结出一套适合在超空泡水洞实验中应用的自动图像获取技术。使用该方法能够自动获取高速摄像图像中的空泡外形和振动周期等参数,并形成数据文件。实验表明,该方法自动化水平高,并具有较好的精度,在实际应用中获得了良好的效果。

High speed digital camera is a powerful tool to record the cavitation phenomenon in cavitation tunnel test. The technology should be able to extract and detect the cavity boundary and its pulsation precisely and has to overcome the influences of interfere from the background and the deflection through air, window and water. These are key problems needed to be solved for unsteady supercavitaion test. The authors have setup a technique, which employs the modern digital imaging processing including modern edge detection technique and can obtain clear and quite precise boundary location. The curves can be drawn automatically from a set of imageries that are taken by high-speed camera. Also presented is a 3X3 filter template used in filter operation for digitally processing the supercavitaion images. This method has been applied to detect the boundary of cavity in supercavitating flow and characterize the unsteady phenomena of supercavitating flow.