Phase, pressure and velocity evolution and atomization characteristics of multiple Faraday waves in ultrasonic atomization: experiments and simulations

Abstract

• Numerical simulation study of the multiple Faraday wave's evolutions. • Pressure difference in the Faraday wave is the internal driving force of fluid flow. • The Faraday wave unstable evolution is essentially an energy conversion process. • The effect of liquid density on atomization characters is predicted by simulation. Ultrasonic atomization has attracted a great deal of attention from the industrial and research communities in recent years. However, current research lacks attention to the internal pressure and velocity fields in the unsteady evolution of multiple Faraday waves, leading to an insufficient understanding of the ultrasonic atomization mechanism. Here, we use computational fluid dynamics to conduct a detailed study of multiple Faraday waves under ultrasonic frequency vibrations, including phase, pressure, and velocity field evolution, and atomization characteristics. In the middle of the ligament, a pressure peak point induced by surface tension induces the capillary pinch-off phenomenon. Essentially, Faraday wave instability evolution is the process of storing, consuming kinetic energy, then converting it into pressure potential energy, and finally into droplet surface energy and kinetic energy. The effects of different parameters (vibration amplitude, vibration frequency, liquid surface tension, viscosity, density, and liquid film thickness) on the atomization characteristics (amplitude threshold, atomization time, and droplet size) are related to this energy evolution. This study provides a new physical explanation of the unstable evolution mechanism of multi-Faraday waves from the perspective of energy conversion, improving the scientific validity of ultrasonic atomization techniques in applications.