Effects of multi-frequency acoustic waves on the agglomeration of fog droplets

Abstract This work focuses on using multi-frequency sound waves to dissipate fog. It is a promising fog-dissipation technique due to its ease of control, flexibility, environmental friendliness, and no interference with traffic flow. This study introduces a novel approach to dissipate artificial fog generated inside an experimental setup utilizing harmonically related multi-frequency acoustic waves. Fundamental frequencies of 300 Hz, 400 Hz, and 500 Hz, along with their 9th, 11th, and 40th harmonics were tested at a maintained Sound Pressure Level (SPL) of 112 dB. Many combinations were found to increase fragmentation of large droplets, which reduces the condensation efficiency. The main mechanism for acoustic condensation seems to be the collision and merging of fog droplets. Most harmonics tested did not improve agglomeration, with the notable exception of the 400 Hz paired with its 9th-harmonic. This combination resulted in a 61.06% reduction in Liquid Water Content (LWC) for large droplets and a 90% condensation effect achieved quicker than all the other cases. These findings highlight the potential of using harmonics for acoustic fog dissipation.