RayleighTaylortype

Rayleigh-Taylor type refers to a family of interfacial instabilities that occur when a density stratification is subjected to acceleration, causing the heavier fluid to push into the lighter fluid. The canonical setting involves two immiscible, incompressible fluids with densities ρ_h > ρ_l arranged with the heavier fluid above the lighter one in a downward gravitational or otherwise directed acceleration field. Small perturbations at the interface grow in time, producing finger-like plumes and rising bubbles that mix the fluids.

In the simplest inviscid, incompressible case, the linear growth rate of a perturbation with wavenumber k is given by gamma ≈ sqrt(A g k), where A = (ρ_h − ρ_l)/(ρ_h + ρ_l) is the Atwood number and g is the acceleration. Real systems include effects that modify this rate, such as surface tension, viscosity, and compressibility. Surface tension tends to stabilize short wavelengths, while viscosity dampens growth; magnetic fields or rotation can introduce additional stabilization or complexity, leading to magneto-Rayleigh–Taylor or rotating RT variants.

Nonlinear evolution leads to complex, turbulent mixing with descending spikes of heavier fluid and rising bubbles of lighter fluid, forming intricate interfacial structures. RT-type instabilities are studied in a wide range of contexts, including fluid mechanics, plasma physics, astrophysics, and high-energy-density experiments. They are central to understanding phenomena such as inertial confinement fusion implosions, supernova remnants, and the mixing of stratified zones in geophysical and astrophysical flows.

Historically, the instability was described by Lord Rayleigh in 1880 and refined by G. I. Taylor in 1950, with the combined term Rayleigh–Taylor instability commonly used to name the phenomenon. The broader “RT-type” formulation emphasizes related interfacial instabilities arising from acceleration-driven density contrasts.