Developing characteristics of the positive streamer in water with microsecond pulse voltage

Underwater discharge is the typical method used to generate plasma in a liquid phase environment and is employed in many engineering applications. This study analyzes the formation and development process of the positive streamer in water under microsecond voltage. The effects of voltage amplitude, liquid conductivity, and the presence of bubbles on the underwater discharge characteristics are analyzed by establishing a two-dimensional finite element simulation model of a needle-plate gap. The simulation results show that the electron density of the streamer in water can reach 10(23) m(-3), and as the applied voltage amplitude increases, the development speed of the streamer increases and the head of the stream bifurcates. Moreover, when the conductivity of the water is high, the development speed of the streamer and the density of charged particles increase. Furthermore, the presence of bubbles significantly impacts the development of the discharge morphology, causing the channel to have multiple bifurcations.