The study of ultrasonic atomization is one of the important factors for fuel spray process in the diesel engine combustion chamber. The droplet characteristics are influenced by liquid properties and vibration frequency. In this study, the phenomenon of droplet formation and droplet size were studied at different frequencies of the ultrasonic atomization processes for water liquid. The ultrasonic atomizer was used for the atomization process to generate droplets. CFD- 2D with the Volume of Fluid (VOF) model was used to study the process of droplet size and droplet formation at different frequencies. Water with constant film thickness and bending vibration at constant vibration amplitude were used in this model. The variation of vibration frequencies is applied from 50 kHz to 200 kHz with 50 kHz increment. The results showed that the number of droplets and the area of droplet formation increases with the increases in the vibration frequency. Effect of vibration frequency to the size of the droplet, time for droplet formation, velocity, and several droplets is more significant at vibration frequency 50 kHz to 100 kHz than vibration frequency from 100 kHz to 200 kHz.
