Unveiling the signature of surface tension on Rayleigh-Taylor turbulence*

The Rayleigh-Taylor instability originates when a heavier fluid is initially placed on top of a lighter fluid in the presence of gravity. The instability then evolves into a self-similar turbulent mixing layer, sustained by the continuous conversion of potential into kinetic energy. If the two fluids are not miscible, the surface tension prevents them to mix at the molecular level. Nevertheless, the turbulence fragments one fluid into the other, generating an emulsion-like state. In this state, the characteristic bubble size decreases in time according to a power law scaling that results from a balance between the rising kinetic energy and the surface energy density. In this contribution we draw a phenomenological picture that describes the Rayleigh-Taylor emulsification process following the prediction of Chertkov, Kolokolov and Lebedev (PRE 2005) and present the first experimental and numerical evidences that challenge this prediction.