| Gas-liquid two-phase flow is one of the most common forms of multiphase flow,which is widely used in the area of energy,chemical,aerospace and so on.The development of gas-liquid two-phase flow field measurement technology and mastering the motion characteristics of gas-liquid two-phase flow are of great significance to improve the efficiency of industrial production.In this work,taking the bubbles in gas-liquid two-phase flow as the research object,a three-dimensional reconstruction method of bubble flow field based on multi-vision is proposed to obtain the three-dimensional spatial distribution of bubbles in the flow field,which lays a foundation for further research on the motion characteristics of bubbles in the flow field.In this work,a set of bubble image acquisition system is designed and built to acquire bubble images.The preprocessing of bubble images are completed by using digital image processing technologies such as grayscale,subtraction processing,binarization and hole filling,which provides high-quality experimental data for the subsequent three-dimensional reconstruction of flow field.A calibration method of trinocular vision is studied for the experimental system built in this work.A set of three camera calibration device is designed to acquire calibration images,and a method named three cameras stereo calibration(TCSC)is proposed in this work,which aims at acquiring the position relationship of the three cameras,the internal parameters,and the external parameters.Rough-Precise Location Simultaneous Algebraic Reconstruction Technique(RPL-SART)based on multi-vision is proposed for 3D reconstruction of bubble flow field.The RPL-SART iterative algorithm integrates rough position based on the results of TCSC calibration to SART algorithm.With the 3D reconstruction method proposed in this work,the strict requirement of projection angle in traditional SART algorithm is avoided,which means there is no constraint on the placement angle of the three cameras and there is no need to measure the angle.Rough location reduces the search range of back projection,which makes the reconstruction method faster.The speed and accuracy of RPL-SART iterative algorithm are verified by simulation experiments.The reconstruction results of bubble flow field based on parallax method and RPL-SART are compared experimentally,which has verified that RPL-SART has higher efficiency in bubble shape description and bubble position calculation.Meanwhile,RPL-SART iterative algorithm can reconstruct overlapping bubbles well to a certain extent. |
