Micro-droplet deposition and growth on a glass slide driven by acoustic agglomeration

Sound waves can be applied on fog elimination due to the acoustic agglomeration phenomena. However, existing studies have different understanding of the effective sound wave frequency and sound intensity for the acoustic agglomeration effect of micro-droplets. This study designs a novel microscopic experiment to visually present the growth process of droplets under the action of sound waves. A group of indexes are also proposed to quantitatively analyze the growing process of micro-droplets under the action of sound waves, such as area-weighted average particle size, relative growth rate of droplets, and relative growth factor of droplets. In addition, a series of experiments with different sound waves are also conducted to explore the impact law of sound frequency and sound intensity on droplet agglomeration. The results verify the acoustic agglomeration effect of micro-droplets by visible processes at microscopic scale and indicate that within the studied sound pressure level (SPL) and frequency range, the droplets’ deposition is faster under the action of sound waves of higher SPL and lower frequency. Most importantly, the critical values of sound wave characteristics for obvious acoustic agglomeration of droplets are presented, providing guidance for choosing effective sound waves in the actual application of acoustic fog elimination.