Experimental investigation on the dynamic behaviors of droplets impacting on ultrasonically vibrating curve surfaces

The present work experimentally investigates the dynamic behaviors of droplets impacting on ultrasonically vibrating curve surfaces. The complicated experimental phenomena, including edge splash, surface splash, capillary wave, cavitation, and sub-droplet rebound, are observed, and the mechanisms behind each phenomenon are revealed. The critical curve of the edge splash is obtained, and the critical vibration amplitudes on curve surfaces are lower than that on flat surfaces due to the aerodynamic force. Using the image processing technique, the expelling efficiency of the ultrasonic vibrating curve surface and the size distribution of secondary droplets are elucidated and discussed. The expelling efficiency increases linearly with the increase of the ultrasonic vibration amplitude, and the impact velocity has almost no influence on the expelling efficiency. A higher excitation amplitude results in a wider secondary droplet size distribution and a larger average size. It is found that the temperature slightly affects the dynamic collision process of the droplets through comparing the experimental results under room temperature and supercooled conditions. Under the supercooled condition, the ultrasonic vibration could still effectively expel the impinging droplets, which shows the potential of the ultrasonic vibration on the waterproof and anti-icing fields.