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Laser-generated Richtmyer–Meshkov and Rayleigh–Taylor instabilities in a semiconfined configuration: bubble dynamics in the central region of the Gaussian spot

The 3D Richtmyer–Meshkov (RM) and Rayleigh–Taylor (RT) instabilities induced by a laser pulse of the Gaussian-like power profile on a metal surface in a ‘covered target configuration’ environment evolve into complex fluid dynamics with the new paradigm of wave-vortex phenomena in turbulent mixing. Such a RM instability (RMI)/RT instability (RTI) environment is generated in a semiconfined configuration (SCC) of the experiment which causes the extended vapor/plasma lifetime and fast multiple reshocks that strike the density interface. The Gaussian power profile causes different circular regions with a different momentum transfer, different Atwood number and different RMI/RTI morphology. In the central region (CR) of the Gaussian-like spot, where the momentum transfer and Atwood number are maximal, the oscillatory field of reshocks causes the separation of small and large bubbles, the growth of bubble penetration depth and of bubble size by the formation of bubble pairs inside the cluster and their merging. Discrete merging jumps give rise to larger bubbles in the process which can be represented by the ‘Lindenmayer tree’.