A three-dimensional Richtmyer–Meshkov instability (RMI) was generated on metal target by the laser pulse of Gaussian-like power profile in the semiconfined configuration (SCC). The SCC enables the extended lifetime of a hot vapor/plasma plume above the target surface as well as the fast multiple reshocks. The oscillatory pressure field of the reshocks causes strong bubble shape oscillations giving rise to the complex wave-vortex phenomena. The irregularity of the pressure field causes distortion of the shock wave front observed as deformed waves. In a random flow field the waves solidified around the bubbles form the broken “egg-karton” structure – or the large-scale chaotic web. In the coherent flow field the shape oscillations and collapse of the large bubbles generate nonlinear waves as the line- and the horseshoe-solitons. The line solitons are organized into a polygonal web, while the horseshoe solitons make either the rosette-like web or appear as the individual parabolic-like solitons. The configurations of the line solitons are juxtapositioned with solitons simulated by the Kadomtsev–Petviashvili (KP) equation. For the horseshoe solitons it was mentioned that it can be obtained by the simulation based on the cylindrical KP equation. The line and the horseshoe solitons represent the wave-vortex phenomena in which the fluid accelerated by the shock and exposed to a subsequent series of fast reshocks follows more complex scenario than in the open configuration. The RMI environment in the SCC generates complex fluid dynamics and the new paradigm of wave vortex phenomena in turbulent mixing.

We present a Rayleigh–Taylor mixing rate simulation with an acceleration rate falling within the range of experiments. The simulation uses front tracking to prevent interfacial mass diffusion. We present evidence to support the assertion that the lower acceleration rate found in untracked simulations is caused, at least to a large extent, by a reduced buoyancy force due to numerical interfacial mass diffusion. Quantitative evidence includes results from a time-dependent Atwood number analysis of the diffusive simulation, which yields a renormalized mixing rate coefficient for the diffusive simulation in agreement with experiment. We also present the study of Richtmyer–Meshkov mixing in cylindrical geometry using the front tracking method and compare it with the experimental results.

We suggest an easily obtained laboratory configuration to observe jet and vortex flows for the Richtmyer–Meshkov (accelerated inhomogeneous flow) environment. A hemispherical bubble in air with density ratio of 5 is placed against an ideally reflecting wall and struck by a planar shock. This also models a spherical bubble struck symmetrically by two identical approaching shocks, that is, a “reshock” configuration. For all Mach numbers (M = 1.2, 1.5, and 2.0), our axisymmetric simulations show that the heavy hemispherical bubble expands axially away from the wall as a jet, and a weaker vortex ring moves radially along the wall. In addition, when M = 1.5, a ringlike vortex projectile (VP) of small diameter follows closely behind the reflected shock and is associated with its moving triple point. This VP contains an entrained shocklet and quadrupole structure of dilatation. Various methods are applied to quantify the emerging coherent structures.

The three-dimensional (3D) turbulent mixing zone (TMZ) evolution under Rayleigh–Taylor and Richtmyer–Meshkov conditions was studied using two approaches. First, an extensive numerical study was made, investigating the growth of a random 3D perturbation in a wide range of density ratios. Following that, a new 3D statistical model was developed, similar to the previously developed two-dimensional (2D) statistical model, assuming binary interactions between bubbles that are growing at a 3D asymptotic velocity. Confirmation of the theoretical model was gained by detailed comparison of the bubble size distribution to the numerical simulations, enabled by a new analysis scheme that was applied to the 3D simulations. In addition, the results for the growth rate of the 3D bubble front obtained from the theoretical model show very good agreement with both the experimental and the 3D simulation results. A simple 3D drag–buoyancy model is also presented and compared with the results of the simulations and the experiments with good agreement. Its extension to the spike-front evolution, made by assuming the spikes' motion is governed by the single-mode evolution determined by the dominant bubbles, is in good agreement with the experiments and the 3D simulations. The good agreement between the 3D theoretical models, the 3D numerical simulations, and the experimental results, together with the clear differences between the 2D and the 3D results, suggest that the discrepancies between the experiments and the previously developed models are due to geometrical effects.

We describe the evolution of the large-scale coherent structure of bubbles and spikes in the Richtmyer–Meshkov instability. Our multiple harmonic analysis accounts for a non-local character of the nonlinear dynamics. A new type of the evolution of the bubble front is found. A comparison to so-called “Layzer-type” local models is performed.

This article reports on the latest experiments in the series of Richtmyer–Meshkov instability (RMI) shock-tube experiments. Previous work described a double-bump experiment that evidenced some degree of unrepeatability. The present work features an enlarged perturbation introduced to improve repeatability. In common with the previous work, the experiments were conducted at shock Mach number 1.26 (70 kPa overpressure), using the Atomic Weapons Establishment 200 × 100 mm shock tube with a three-zone test cell arrangement of air/sulphur hexafluoride/air. The sulphur hexafluoride gas (SF6) was chosen for its high density (5.1 relative to air) providing an Atwood number of 0.67. Gas separation was by means of microfilm membranes, supported by fine wire meshes. A double-bump perturbation of two-dimensional geometry was superimposed on the downstream membrane representing a 0.6% addition to the dense gas volume. Visualization of the turbulent gas mixing was by laser sheet illumination of the seeded SF6 gas using a copper vapor laser pulsing at 12.5 kHz. Mie scattered light was recorded using a 35-mm rotating drum camera to capture a sequence of 50 images per experiment. Sample experimental results shown alongside corresponding three-dimensional hydrocode calculations highlight the problems in both analysis and comparison caused by multiple scattering arising from the necessary use of a high seeding concentration. Included is a demonstration of the effectiveness of introducing into the hydrocode a Monte Carlo-based simulation of the multiple scattering process. The results so derived yield greatly improved qualitative agreement with the experimental images. Quantitative analysis took the form of deriving relative intensity data from line-outs through experimental images and their code equivalents. A comparison revealed substantial agreement on major features.

This article reports the first Richtmyer–Meshkov instability experiments using an improved version of the Atomic Weapons Establishment convergent shock tube. These investigate the shock-induced turbulent mixing across the interfaces of an air/dense gas/air region. Multipoint ignition of a detonatable gas mixture produces a cylindrically convergent shock that travels into a test cell containing the dense gas region. The mixing process is imaged with shadowgraphy. Sample results are presented from an unperturbed experiment and one with a notch perturbation imposed on one of the dense gas interfaces. The unperturbed experiment shows the mixing across the dense gas boundaries and the motion of the bulk dense gas region. Imposition of the notch perturbation produces a mushroom-shaped air void penetrating the dense gas region. Three-dimensional simulations performed using the AWE TURMOIL3D code are presented and compared with the sample experimental results. A very good agreement is demonstrated. Conducting these first turbulent mixing experiments has highlighted a number of areas for future development of the convergent shock-tube facility; these are also presented.

The late-time growth rate of the Richtmyer–Meshkov instability was experimentally studied at different Atwood numbers with two-dimensional (2D) and three-dimensional (3D) single-mode initial perturbations. The results of these experiments were found to be in good agreement with the results of the theoretical model and numerical simulations. In another set of experiments a bubble-competition phenomenon, which was observed in previous work for 2D initial perturbation (Sadot et al., 1998), was shown to exist also when the initial perturbation is of a 3D nature.

The present article describes an experimental study that is a part of an integrated theoretical (Rikanati et al.2003) and experiential investigation of the Richtmyer–Meshkov (RM) hydrodynamic instability that develops on a perturbed contact surface by a shock wave. The Mach number and the high initial-amplitude effects on the evolution of the single-mode shock-wave-induced instability were studied. To distinguish between the above-mentioned effects, two sets of shock-tube experiments were conducted: high initial amplitudes with a low-Mach incident shock and small amplitude initial conditions with a moderate-Mach incident shock. In the high-amplitude experiments a reduction of the initial velocity with respect to the linear prediction was measured. The results were compared to those predicted by a vorticity deposition model and to previous experiments with moderate and high Mach numbers done by others and good agreement was found. The result suggested that the high initial-amplitude effect is the dominant one rather than the high Mach number effect as suggested by others. In the small amplitude–moderate Mach numbers experiments, a reduction from the impulsive theory was noted at late stages. It is concluded that while high Mach number effect can dramatically change the behavior of the flow at all stages, the high initial-amplitude effect is of minor importance at the late stages. That result is supported by a two-dimensional numerical simulation.