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Microscopic experimental study on acoustic agglomeration of the droplets on wall

Li Fang-Fang (College of Water Resources & Civil Engineering, China Agricultural University, Beijing, China)
Huang Chen (College of Water Resources & Civil Engineering, China Agricultural University, Beijing, China)
Xie En (College of Water Resources & Civil Engineering, China Agricultural University, Beijing, China)
Wang Guang-Qiang (State Key Laboratory of Hydroscience & Engineering, Tsinghua University, Beijing, China + State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, China)
Qiu Jun (State Key Laboratory of Hydroscience & Engineering, Tsinghua University, Beijing, China + State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, China), aeroengine@tsinghua.edu.cn

Study on the effect of acoustic wave on droplet collision-coalescence process is interesting and helps to better understand the acoustic agglomeration mechanism. This study designs and carries out a microscopic experiment to investigate the effect of acoustic wave on wall droplet collision-coalescence process. The derived microscopic images of droplets under the action of different sound waves at different moment are processed and analyzed by binaryzation with iterative threshold, cavity filling, morphological open arithmetic processing, and identification of connected regions, etc. Using a newly defined parameter, equivalent droplet size, the growth rates of the droplets in natural state and under the action of different acoustic parameters are compared and analyzed. The results show that the effect of sound wave greatly accelerates the collision-coalescence process of the droplet, and comparing with sound pressure level, the frequency of the sound wave is a more effective parameter in promoting the collision-coalescence process of wall droplets, and the lower the acoustic wave frequency results in larger collision-coalescence rate.

Keywords: droplet collision-coalescence process, microscopic image processing, acoustic agglomeration, acoustic frequency, sound pressure level