Electrohydrodynamic surface waves of thin oil films generated by needle–plate barrier discharges under reduced gas pressures

The study of electrohydrodynamically (EHD) induced surface wave phenomena on the surface of dielectric thin oil films under needle–plate barrier discharges for reduced gas pressure environments has been investigated experimentally. Experiments were conducted in a closed environmental chamber maintained at gas pressure from 0.1 to 760 Torr. The test system consisted of needle corona electrode air gaps, thin mineral oil films, polymer sheet and metal grounded plate. DC (on/off) negative and positive voltages were imposed on needle electrode. Measurements of corona current waveform and surface wave were observed by current transformers and CCD video camera, respectively. The results show that thin oil film started to deform immediately when DC voltage was imposed and after voltage was off, and that a formation of depression expanding waves was observed even when gas pressure was reduced to 500 Torr.