Molecular dynamics simulation study on the pressure and temperature evolution of ultrasonic cavitation bubbles

This study uses molecular dynamics simulations to examine how varying frequencies and amplitudes of ultrasonic vibration affect the temperature and pressure of cavitation bubbles at the atomic scale. A three-dimensional model of water, gas molecules, and metal atoms was developed using LAMMPS code. The microcanonical ensemble (NVE) and isothermal-isobaric ensemble (NPT) were employed to track the evolution of cavitation bubble temperature and pressure in response to tool head vibrations. The findings show that cavitation bubbles experience significant temperature and pressure increases during oscillation, with these parameters varying noticeably across different vibration amplitudes and frequencies. At lower amplitudes, pressure fluctuations are more intense and erratic, while at higher amplitudes, pressure peaks are higher but exhibit smoother changes. Further analysis indicates that a specific combination of amplitude and frequency can optimize pressure and temperature outputs, highlighting the mechanisms of thermal and mechanical softening in ultrasonic cavitation. This study offers valuable atomic-scale insights into the cavitation effects that occur in ultrasonic machining.