The “Saturn-rings” instability: streaming from the equator of a drop in a uniform electric field*

Drops in electric fields or flow can develop pointy ends emitting thin threads (tip-streaming). The instability results from destabilization of the interface near a stagnation point of a convergent flow. I will present experimental realization of a streaming due to stagnation line instability. A drop placed in a uniform electric field flattens and develops a sharp edge around the equator, which is the stagnation line of the electrohydrodynamic flow. The flow draws from the rim a thin sheet which destabilizes and sheds fluid threads encircling the drop. Subsequently the fluid rings breakup, due to capillary instability, into droplets. The rim streaming creates visually striking “Saturn-rings” around the equator of a drop.