Study On Image Measurement Method For Bubble Motion In Water Flow

Focusing on image measurement method for bubble in multiphase flow, theoretical and experimental studies have been made in this paper systematically and comprehensively. This research is supported by National Science Foundation of China.Using digital image processing technique to process the solid-gas-water three-phase flow image and separate dispersed phase from the three-phase flow image, author calculated the bubble number, particle number in instantaneous image, area of bubble image and other parameters, and analyzed the effect of image enhancement, image segmentation, image analysis and other problems existed in bubble image processing.A set of experimental system was designed to in measure water-gas two-phase flow and influence factors in bubble image analysis was discussed.For the first time, author proposed a quantitative method of evaluate bubble image, and obtained optimal water-gas two-phase image illumination scheme through comparative experiment.The paper brings forward new bubble boundary identification method for High resolution bubble image, which can automatically receive bubble' s closed boundary. Since this method is not sensitive to image noise, it has some robust.The paper also proposed a new method based on dynamic image process for multi-bubble image with complex background. Since this method can automatically pick up background bubble, it promotes the bubble image identity efficiency caused by noise brought by unstable or un-uniform light, scrapes on glass surface, bead and other reasons. This method has some advantages not only in process efficiency but also in precision compared with single image segmentation method.This paper also introduces two basic PIV algorithms to study bubble image and results in better consequences, and analyses the application of these methods and their features. For non-overlap bubble case, this paper brings forward a PIV algorithm to reach bubble velocity and bubble size.