Movement and acoustic radiation of a rising bubble from combustion of pyrotechnic mixtures using experiment and image processing method

Bubble volume and bubble geometry are key parameters that affect the movement and acoustic radiation performance of bubble columns. This paper proposes an image processing method to study the movement and acoustic radiation characteristics of the rising bubbles originating from the combustion of a pyrotechnic composition based on high-speed photography. Results showed that during the rise of bubbles, their shape gradually changed from spherical to irregular, and their rising trajectory presented a curvilinear form. After the rising velocities of the bubbles in the z and x directions were compared, the results revealed that the rising velocity of the bubbles was unstable. The velocity of the rising bubbles in the direction of the z axis was much higher than that of the x axis. Meanwhile, the acceleration of bubble volume decreased first and then increased. This process was repeated; however, the amplitude of increase or decrease was inconsistent, which led to the generation of a certain amount of acoustic radiation effect, and it had a similar trend of change with the acceleration of bubble volume.