Building water bridges in air: Electrohydrodynamics of the Floating Water Bridge

摘要

The interaction of electrical fields and liquids can lead to phenomena thatdefies intuition. Some famous examples can be found in Electrohydrodynamics asTaylor cones, whipping jets or non-coalescing drops. A less famous example isthe Floating Water Bridge: a slender thread of water held between two glassbeakers in which a high voltage difference is applied. Surprisingly, the waterbridge defies gravity even when the beakers are separated at distances up to 2cm. In the presentation, experimental measurements and simple models areproposed and discussed for the stability of the bridge and the source of theflow, revealing an important role of polarization forces on the stability ofthe water bridge. On the other hand, the observed flow can only be explaineddue to the non negligible free charge present in the surface. In this sense,the Floating Water Bridge can be considered as an extreme case of a leakydielectric liquid (J. R. Melcher and G. I. Taylor, Annu. Rev. Fluid Mech.,1:111, 1969).