Numerical simulation is carried out to study the phenomena of droplet formation,diameter and size distribution in ultrasonic atomization process as the effect of different vibrating surface.Differ from the ultrasonic common vibrating surface of nozzle spray structure,flexural radial curvature vibration of bending tube model is proposed to generate droplet spray atomization.Various tube lengths are applied to study the effect of different curvature radius.Longitudinal vibration on flat surface vibration of ultrasonic nozzle spray is also investigated for comparison.Volume of Fluid(VOF)of ANSYS FLUENT was applied to perform ultrasonic atomization process in 2D model.In this study,ultrasonic frequency is set to 70 kHz at constant maximum amplitude for all case studies.In this simulation is found that flexural radial curvature vibration could generate nearly equivalent droplet diameter with flat surface vibration and have narrower distribution,whereas the curvature vibration shape affects the droplet size distribution.