Experimental study on rose-window instability in dielectric liquids induced by corona discharge

Electrohydrodynamic (EHD) instability at the interface of immiscible two-phase systems constitutes a fundamental scientific problem with substantial application prospects in areas including droplet manipulation, electrospraying, and biomedical engineering. In this work, an experimental study was performed to investigate the rose-window instability (RWI) induced by the corona discharge mechanism in dielectric liquids under a needle–plate electrode configuration. By systematically varying the needle electrode voltage, liquid layer thickness, needle–plate distance, dielectric liquid viscosity, and electrode properties, the physical laws governing the primary and secondary RWI were summarized in detail. Experimental results show that as the needle electrode potential increases, the range of the RWI expands. A critical liquid layer thickness of 0.6 mm is identified for 1000 mm/s2 silicone oil, at which the RWI transits from secondary instability to primary instability. Liquid viscosity strongly affects the RWI lattice morphology, and wavy concave folds at lattice boundaries are observed for the first time in low-viscosity liquids. A preliminary investigation was conducted on the effect of electrode properties on the RWI. It was found that the critical voltage for the initial occurrence of instability under negative corona discharge is lower, and when the voltage increases to a certain level, two modes of the instability range of the RWI emerge.