Liquid-phase disturbance exerts a significant influence on the pre-breakdown process of underwater discharge; however, the understanding of its evolution and self-stabilization mechanisms remains insufficient. This study investigates the spatiotemporal evolution and overall expansion characteristics of the liquid-phase disturbance under various conductivity and voltage conditions, and further establishes a predictive model for the gap electrical power and temperature rise of the disturbed liquid phase. The results reveal that, as the discharge develops, both the deposited electrical energy and expansion volume of the liquid phase disturbance exhibit a slowly accelerating growth trend, whereas the average temperature initially rises rapidly and then approaches saturation. Under high liquid conductivity, the liquid-phase disturbance expands more rapidly, but the reduced development time constrains its overall expansion range. In addition, in the later stage of underwater discharge, the disturbed phase is compressed by the streamer, forming a layered structure. Further analysis indicates that the evolution of the liquid-phase disturbance follows an electrothermal flow field coupled feedback mechanism, which drives its temperature distribution toward uniformity and stability, indicating self-stabilization. Moreover, at a fixed liquid conductivity, higher applied voltage leads to a decrease in both the deposited energy and expansion volume of the disturbed phase at bubble formation onset, while the average temperature rise remains nearly constant; meanwhile, increasing conductivity produces a slightly elevated average temperature rise. Finally, the development of the liquid-phase disturbance exhibits a pronounced polarity effect: under negative voltage polarity, its evolution becomes more intense, and the average temperature rise is higher.
Li et al. (Sun,) studied this question.