稀疏泡状流中变形气泡的三维图像测量技术

An image-based technique for measurement of three-dimensional bubble deformation in dilute bubbly flows

研究气泡变形对于分析泡状流中气泡的受力和运动具有重要意义。设计了一种可确定稀疏泡状流中气泡空间坐标与变形参数的图像测量技术:原始图像经预处理和增强后,结合形态学方法识别出变形气泡投影的闭合轮廓。改进了分水岭方法对气泡投影进行分割,并用对称直线法确定投影中心改进Hough变换,得到椭球气泡模型的投影椭圆参数。提出了一种由两幅投影轮廓重构三维气泡模型的算法并分析了实验误差。该技术可较准确地测得气泡空间坐标和变形参数:投影椭圆的参数误差小于3个像素,气泡识别误差小于15%。

An image-based technique has been developed to measure the three-dimensional deformation of a bubble in a dilute bubbly flow in order to investigate forces on the bubble and its lateral motion induced by the forces. Based on the mathematical morphology principles, an edge-detection technique was used to fred the projection contours of the deformed bubble from the bubble image which was preprocessed and enhanced in advance. The shadow image of the bubble was segmented by an improved watershed method, and then the centroid of the bubble shadow was detected using the symmetric lines method which could speed the Hough transform for determination of the elliptical projections of the deformed bubble. Finally an algorithm was proposed for reconstructing the three-dimensional bubble shape from the two elliptical projection contours. The error analysis showed that the difference between the calculated projection contour and the real one is less than 3 pixels and the error of the number of detected bubbles is less than 15%. The results showed that the imagebased technique for measurement of the bubble deformation is valid and accurate.