Richtmyer–Meshkov instability

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A three stage transition from a shock-accelerated layer with deterministic vortex-dominated growth, followed by a regime featuring both deterministic and stochastic growth of small-scale features, and ending with turbulent mixing of the layer with surrounding air.

The Richtmyer–Meshkov instability (RMI) occurs when an interface between fluids of differing density is impulsively accelerated, e.g. by the passage of a shock wave. The development of the instability begins with small amplitude perturbations which initially grow linearly with time. This is followed by a nonlinear regime with bubbles appearing in the case of a light fluid penetrating a heavy fluid, and with spikes appearing in the case of a heavy fluid penetrating a light fluid. A chaotic regime eventually is reached and the two fluids mix.

During the implosion of an inertial confinement fusion target, the hot shell material surrounding the cold D-T fuel layer is shock-accelerated. Mixing of the shell material and fuel is not desired and efforts are made to minimize any tiny imperfections or irregularities which will be magnified by RMI.

At an entirely different scale, stellar core materials (e.g. Cobalt-56) from Supernova 1987A were observed earlier than expected, giving evidence of turbulent mixing due to Richtmyer–Meshkov and Rayleigh–Taylor instabilities.

Between these two extremes, supersonic combustion in a Scramjet may benefit from RMI as the fuel-oxidants interface is enhanced by the breakup of the fuel into finer droplets.

The study of deflagration to detonation transition (DDT) processes show that RMI-induced spontaneous flame acceleration can result in detonation.

RMI can be considered the impulsive-acceleration limit of the Rayleigh–Taylor instability.

R. D. Richtmyer provided a theoretical prediction in "Taylor instability in a shock acceleration of compressible fluids", Communications on Pure and Applied Mathematics 13, 297-319 (1960).

E. E. Meshkov (Евгений Евграфович Мешков) provided experimental verification in "Instability of the Interface of Two Gases Accelerated by a Shock Wave", Soviet Fluid Dynamics 4,101-104 (1969).

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