The Study And Application Of Nuclei Measurement By Interferometric Laser Imaging

The existed cavitation researches have showed that the nuclei in the water are the fundamental condition for cavitation inception and also have remarkable influence on the process of cavitation. In order to know well about the relationship between nuclei and cavitation, some measurement methods have been used to determine the nuclei size and distribution. But up to now it is still an open problem about how the nuclei affect the cavitation. One of the reasons is lack of the effective way to measure the nuclei of incoming flow in cavitation facilities in real time. One other hand, seeding nuclei to the cavitation tunnel is often used to reduce the scale effects in the cavitation experiment. In this case nuclei measurement is also necessary technology to control the nuclei seeding in cavitation tunnel.In the present paper interferometric laser imaging system based on the PIV hardware equipments was set up to measure the nuclei distribution, and the image processing programs were developed to try to obtain the measurement results in real time. As the application this measurement was applied to the nuclei seeding system which is the key equipment for newly-built cavitation tunnel of CSSRC. The present work will provide a base to the nuclei control in the cavitation tunnel.Firstly, according to basic principle of interferometric laser imaging, some analysis was carried out to establish the formula of the bubble diameter in the front scattering field and side scattering field respectively. And then the image processing programs, which primarily include to pick up the bubble image and solve the problems of bubble overlap in a image, was developed to try to obtain the measurement results automatically in the Matlab environment.Secondly, some discussions were made about the influence of system parameters on the measurement, as the interferometric laser imaging technology was employed to measure the micro-bubbles generated by electrolysis. The factors include scattering angle, collecting angle and magnification etc.. The measurement results were also validated by microphotographics method in the same experimental conditions.Finally, the interferometric laser imaging technology was applied to the nuclei seeding system and measured nuclei spectrum under the different mixture pressure and seeding flux conditions. The capability of nuclei seeding system was deduced from the measurement results. The results can provide a technology fundament to the application of the interferometric laser imaging method and the nuclei seeding system on the cavitation tunnel.