Electrohydrodynamic instabilities of a weakly-conducting liquid bridge

We study the effect of a uniform DC electric field on the dynamics of a liquid bridge. The fluid is Hexadecane oil containing different quantities of AOT. As the field strength increases, we observe first that the contact line becomes unstable, adopting an undulating flower-like shape, and then the appearance of a travelling wave in the azimuthal direction. We study these instabilities as a function of fluid conductivities, field strengths and size of the bridge. The experiment is complemented by theoretical analysis, following Malkus and Veronis, Physics of Fluids (1961).