Instability and collapse mechanisms of O2 and N2 nanobubble gas–liquid interfaces: A molecular dynamics simulation study

Nanobubbles, with their stability and oxidative properties, are widely applied in biomedicine, flotation, and environmental remediation. While experimental studies have explored their application effects, the dynamic behavioral characteristics of gas-containing nanobubbles during collapse remain insufficiently investigated. This study employs molecular dynamics simulation to examine nanobubble collapse under various conditions, including impact velocities, gas types, bubble sizes, and gas densities. Results show that increasing bubble size expands the microjet radiation area, while higher impact velocities increase microjet velocities. Gas types affect the jet radiation area due to differences in van der Waals forces and solubility. Vacuum nanobubbles exhibit higher maximum jet velocities than nitrogen and oxygen nanobubbles. Gas cushioning and compression rebound significantly influence maximum jet velocity. Microjets induce vortex structures, gas surface changes, and local pressure increases, leading to secondary water hammer impacts. Simulation results align well with theoretical calculations. This study provides the theoretical foundation for the industrial-scale implementation of nanobubble cavitation technology.