Large and Small Scale Structure in Rayleigh-Taylor Mixing

Laser-induced fluorescence is used to image the central plane of the mix region of two immiscible liquids subject to the Rayleigh-Taylor instability at an acceleration of 70 times Earth's gravity. The size of the mixing zone grows with coefficient αb0.054. Individual bubbles are clearly resolved and their structure is measured. The widths of the bubbles are narrower than recent models predict. An internal structure in the bubbles appears after the mixing zone is established. This structure suggests a cascade to small wavelengths. The cascade is required for molecular mix.