Interface coupling and growth rate measurements in multilayer Rayleigh-Taylor instabilities

Magnetic levitation was used to measure the growth rate Sigma vs wave vector k of a Rayleigh-Taylor instability in a three-layer fluid system, a crucial step in the elucidation of interface coupling in finite-layer instabilities. For a three-layer (low-high-low density) system, the unstable mode growth rate decreases as both the height h of the middle layer and k are reduced, consistent with an interface coupling proportional to e(-kh). The ratios of the three-layer to the established two-layer growth rates are in good agreement with those of classic linear stability theory, which has long resisted verification in that configuration.