Analysis of Streamer Propagation for Electric Breakdown in Liquid/Bioliquid

There is an increasing interest in the study of direct plasma generated in liquid/ bioliquid as it fi nds more applications in both industry and academic research. For all the applications, it is important to get a better understanding of the key physical mechanisms of the breakdown process. In the present paper, streamer propagation during an electric breakdown process of dielectric liquid was analyzed quantitatively using two different mechanisms based on electrostatic expansion and local heating. It was proposed that at the early stage of the streamer propagation, the electrostatic force due to the charging of a liquid-gas interface under a high electric fi eld might be the major driving force for fi lament growth. Over a submicrosecond time scale, the local heating might dominate the streamer propagation process, and the growth of the fi lament could be caused by the continuous evaporation of liquid at the tip of the streamer. Analysis of linear instabilities that lead to the bushlike growth of the streamers was carried out. Both classic Rayleigh-Taylor instability and electric fi eld–induced instability were identifi ed. It was shown that with an increasing applied voltage, the electrostatic instability was enhanced, whereas the Rayleigh instability was suppressed.