Research On Digital Image Measurement Method Of Bubble Motion

In today's world, an important research in Environmental Hygiene is to create and introduce new technology and methods in this field. Due to the various forms and transmission routes of harmful environmental factors, therefore, studies on the transmission ways, speed, concentration of pollutants have become the research foundations to the pollutant control measures, and to explore new laboratory measuring techniques is also critical.This study designed a mimic lab device of aeration tank flow field, and put the two-phase flow field of bubble flow in quiescent water into our research focus, using Particle Image Velocimetry(PIV) to study the Digital Image Processing technique on the dimensions of gas bubbles, and the concentration distribution etc. Thus, to provide the prerequisite work for the further research on the flow status of two-phase flow field existing pollutants, the dimensions and concentration of particle, and to recognize its flow rules.Through the research on the Digital Image Measurement technique and two-phase flow measurement, in together with the mimic experiment of aeration tank, the following results were gained:(1) Digital Image Measurement technique is an instant and non-disturbing whole-field velocity measurement, the pictures captured involved massive information on particle, when using proper Digital Image Processing technique, some parameters, such as the bubble dimensions, concentration distribution can be obtained.(2) Through the designed mimic lab device of aeration tank, the gas-liquid two-phase flow measurement and its analysis system were built up. It made the best light source and its position, applying the proper photographing method, combining the liquid flow condition, and obtained a series of original image of high quality gas bubbles.(3) By using MATLAB to analyse the captured pictures, an effective Digital Image Measurement method on two-phase flow was found. By using the adaptive histogram equalization, gray transformation and non-uniform background correction to the original gas bubble image, the clarity of the pictures was dramatically improved. The research applied multi-threshold image segmentation, accurately separated the gas bubbles from the background, and marked them, so that to get the statistical function of parameters, such as gas bubble dimensions and concentration, and finally gained the information of gas bubble dimensions and concentration distribution.