Numerical investigation of underwater discharge generated in a single helium bubble at atmospheric pressure

In this work, a two-dimensional axisymmetric numerical modeling of underwater discharge in a single helium bubble at atmospheric pressure was performed. The dynamics of the discharge ignition, propagation in the bubble, and the formation of reactive oxygen species (ROS) (O, OH, and H2O2) were studied. Upon ignition, the discharge propagated mainly along the gas-water interface until a circle adjacent to the internal surface of the bubble was formed. OH was found to be the dominant ROS in the bubble, followed by O and then H2O2. The influence of the voltage amplitude and the position of the needle electrode on the discharge development, reactive species, and corresponding fluxes to the gas-water interface was also investigated. At low voltage, the discharge was confined inside the bubble with a standoff distance from the gas-water interface. When the voltage was higher, the discharge was ignited earlier and the propagation path of discharge was closer to the gas-water interface, resulting in the enhancemen...