Topic 6

• 学生：滕晓锟 朱冰冰 刘继聪
• 指导教师：姚红英

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on the surface of the liquid. Explain and investigate this phenomenon.

1. V. V. Mayer, E. I. Varaksina, and V. A. Saranin. Simple lecture demonstrations of instability and self-organization. Phys. Usp. 57, 1130–1135 (2014)simple_lecture_demonstrations_of_instability_and_self-organization.pdf
2. C. S. Herrick. Electroconvection cells in dielectric liquids interfaced with conducting fluids. Proc. Royal Soc. A 336, 487–494 (1974)electroconvection_cells_in_dielectric_liquids_interfaced_with_conducting_fluids.pdf
3. H. A. Pohl. Some Effects of Nonuniform Fields on Dielectrics. J. Appl. Phys. 29, 1182 (1958)some_effects_of_nonuniform_fields_on_dielectrics.pdf
4. A. T. Pérez. Electrohydrodynamic instabilities in dielectric liquids induced by corona discharge. In: Conduction and Breakdown in Dielectric Liquids, 12th Int. Conf., 126–129 (1996) electrohydrodynamic_instabilities_in_dielectric_liquids_induced_by_corona_discharge.pdf
5. F. Vega and A. T. Pérez. Corona-induced electrohydrodynamic instabilities in low conducting liquids. Exp. in Fluids 34, 726–735 (2003)corona-induced_electrohydrodynamic_instabilities_in_low_conducting_liquids.pdf
6. R. Chicón and A. T. Pérez. The stability of a horizontal interface between air and an insulating liquid subjected to charge injection. Phys. Fluids 26, 034103 (2014)the_stability_of_a_horizontal_interface_between_air_and_an_insulating_liquid_subjected_to_charge_injection.pdf
7. Wikipedia: Corona discharge, https://en.wikipedia.org/wiki/Corona_discharge
8. Wikipedia: Dielectrophoresis, https://en.wikipedia.org/wiki/Dielectrophoresis
9. Simple lecture demonstrations of instability and self-organization (youtube.com, from Ivan Sadovsky, Nov 28, 2014), https://youtu.be/KNnnqM0H5bs
10. 阶跃电压下液体电介质击穿过程数值分析_王正伟，阶跃电压下液体电介质击穿过程数值分析_王正伟.pdf
11. 液体介质击穿机理研究进展_黄文力，液体介质击穿机理研究进展_黄文力.pdf
12. 第三讲高电压下固_液体介质的绝缘特性_严璋第三讲高电压下固_液体介质的绝缘特性_严璋.pdf

经过两次预实验的观察以及两次对课题的讨论分析，现有几个关键的现象以及之后的探究计划： 关键现象：

• 突变电压的存在。当两电极间的电压达到某一水平之前，液面逐渐出现大凹陷（以针尖正下方为中心周围型分布，正中心位置没有）；电压继续增大至某一值（只与油厚度、电极间距等有关）时，针尖正下方液面突然出现巨大形变、形成蜂巢状自组织结构。
• 电流对页面形状的及电压的敏感性。特定电压下，电流或出现较大、非涨落式的变化。
• 电极间距增加时（试验中使用了15cm），蜂巢中单元凸起能长时间稳定存在，并且大小形状及其相近，对油层厚度和电压的要求亦不太严格（3mm以内油层厚度，10kV左右电压即可），从而便于研究。

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