Imploding and exploding circular EHD solitary waves propagating onto an insulating dielectric liquid layer

We present here an extensive experimental study on an EHD phenomenon discovered recently [1]: a wave created and propagating at the surface of an insulating liquid film deposed on a polymer sheet lying itself on a metallic electrode, when switching off the corona effect produced by a point facing the layers onto the metallic plate. If now we modify the experiment by having a pin-hole drilled through the sheet at the center, a second wave simultaneously appears, and this one driving inward. Video recording and image analysis combine to characterize the phenomenon in terms of the relevant parameters. From recordings, the wave velocities have been measured: they decline with wave propagations, the decay decreasing with the charging voltage level. The effects of point-plane separation and of liquid viscosity are also investigated. In addition, the main features of corona pulsing during both the precharging phase and the subsequent wave-discharging phase have been examined. A rough analysis giving an explanation of the basic phenomenon is also presented.