Parallel streamer discharges between wire and plane electrodes in water

Underwater Discharge Phenomena in Inhomogeneous Electric Fields Caused by Impulse Voltages

“…The electric field around the tip of the needle electrode, or the streamer channel, is highly increased, which causes an intense field emission current that eventually vaporizes the water. Also, the very high electric field causes a cavity due to the electromechanical stress, which is proportional to the square of the electric field strength [9], [13].…”

“…The average propagation velocity during steps for positive streamers is approximately 60 times faster than that for negative streamers, but it is much less than the drift velocity for electrons in water vapor at room temperature [20]. Katsuk, et al [9] have reported that the propagation velocities of positive streamer discharges between wire and plane electrodes in tap and distilled water have almost the same values of 32 mm/㎲, despite the different appearances of the discharges. In addition, the propagation velocity stays almost constant during the time that the voltage is applied, despite the fact that the distance between the streamer head and the plane electrode reduces with time.…”

“…The average streamer propagation velocity is constant during the time that the voltage is applied and has almost identical values for different voltages. This effect is explained by considering the energy flow into the streamer head and its effect on the thermal expansion of the head [9]. The slow streamer can indicate a streamer filled with microbubbles of multiple sizes, that is, new phases of water are formed.…”

“…Streamer discharge phenomena in water are known to be influenced by various factors, such as gap geometry, water conductivity, pressure, pulse duration, polarity, and amplitude of the applied voltage [6]- [9]. It is generally assumed that "thermal" processes are associated with microsecond breakdown liquids, and "electron avalanche" processes are closely associated with the underwater discharges over shorter time scales.…”

“…It is also important to determine whether an electron avalanche can occur in water at the breakdown fields [10]- [12]. The pre-breakdown growth is likely to proceed via electron avalanche in the bubbles that are present in the water [8]- [9]. An issue of fundamental breakdown is whether or not an electron avalanche can occur in the liquid water at the breakdown.…”