This paper presents the results of an experimental study of ejection and dispersion of a lead sample in vacuum after shock-wave loading and isentropic unloading using optoelectronic microscopy and photonic Doppler velocimetry. The dynamics and spectrum of predominantly dispersed particles are studied. Optical visualization is ensured by cutting out an 0.5-mm wide stream from the dispersed cloud using a diaphragm with a slit. The experiments are carried out in a sealed armored chamber. A 1- or 2.5-mm thick sample is loaded with a solid explosive through a metal substrate 1 and 2 mm in thickness. The shock wave intensity varies from about 23 to 38 GPa, and the pressure gradient behind the wave front ranges from 80 to 157 GPa/cm. After the loading, the lead is either in a liquid phase, in a solid phase, or in a mixture of both. It is shown that the particle size distributions of dispersed lead are different at different phase states.

This paper presents experimental and calculated results of studying the development of turbulent mixing at the air–water interface after the passage of an oblique shock wave. The shock-wave Mach number in the experiments was varied in the range 2–2.3. The angle of inclination of the shock wave front to the interface was 0, 15 ^∘ , and 30 ^∘ . When the shock wave was incident on the water surface, Kelvin–Helmholtz instability developed, which over time led to turbulent mixing of the substances in contact. In the experiments, the flow field structure was recorded by high-speed video cameras. It was found experimentally that with increasing angle of incidence of the shock wave on the interface, turbulent mixing increased and the droplet size of the dispersed liquid decreased due to more intense droplet fragmentation. Numerical simulation of the experiments using a two-dimensional technique satisfactorily predicted the dynamics of the turbulent mixing zone in the vicinity of the interface.

The fragmentation of a drop of liquid (water, alcohol, glycerin) under the action of an air shock wave with a pressure of 0.2 and 3.2 atmg is studied experimentally and theoretically. The experiments are carried out using an air shock tube, and the liquid drop diameter is approximately 0.6 and 2 mm. The process is studied using high-speed video recording. Dispersed liquid particles from ≈5 μm in size are detected, liquid particle size distributions are plotted, and the particle velocities are determined. The experimental results are compared with the results of computational–theoretical estimation.

This paper presents the results of experimental and computational studies of instability development and mixing at the contact boundaries between gases of different densities. It has been shown that instability and mixing at two contact boundaries in a three-layer gas systems occur after a shock wave with a Mach number M = 1.3 that forms on the left end and moves along the tube has passed through the contact boundaries. Two experiments were performed, in the first of which the central layer was filled with a heavy gas (SF6 gas), and in the second experiment, it was filled with a light gas (helium). On the left and right of the central layer was air at atmospheric pressure. A comparison of the results was performed.

A laboratory experimental complex is presented, with which it is possible to study hydrodynamic instabilities and turbulent mixing with a micron spatial resolution and a nanosecond time resolution and then to process results with high precision. The arrangement of the complex and instrumentation is shown. The complex has been used to study turbulent mixing zones that develop under Rayleigh–Taylor and Kelvin–Helmholtz instabilities at gas–liquid interfaces and Richtmyer–Meshkov instabilities at an interface of gases. New results have been obtained: thin micro-cumulative liquid jets can be ejected from the turbulent mixing zone; after the passage of a shock wave through the zone of turbulent mixing of gases the zone tends to be homogeneous and the shock wave is distorted and expanded. The sizes of fluid particles in the zone of turbulent mixing of substances have also been determined.

The results of experimental studies of the shock-induced particle ejection (“dusting”) from a free rough ( R z = 20) surface of lead and copper samples into an evacuated medium are presented. The experimental methods were based on different physical principles. To determine the size of particles by shadow laser-optical imaging more efficiently, a narrow strip was isolated in the center of the free surface of a sample from which an optically transparent stream of particles was ejected. The rest of the surface, substantially larger in size, ejected particles, parameters of which were reliably recorded using optical heterodyne interferometry detection, radiographic imaging, and piezoelectric techniques. This made it possible to obtain more reliable data on the particle size distribution, the velocity of the front of a particle flux, and the density (weight) distribution of the flow in the direction of its motion, necessary to refine the existing models and create more reliable models to describe the phenomenon. Using lead and copper samples, the material of which melts or does not melt under shock wave loading in selected close conditions (amplitude of the shock wave and roughness of the free surface), made it possible to clearly demonstrate the effect of melting on the qualitative pattern and quantitative characteristics of the shock-induced dusting process.

This paper presents the results of an experimental study of particle ejection into low (0.05 atm) vacuum from a narrow (0.2–0.8 mm) rough ( Rz = 20–50 μm) surface of a lead sample subjected to a shock wave of intensity about 17 and 34 GPa. The ejecta was recorded with a video camera in the microscopic mode with short laser irradiation. Due to the small optical thickness of the ejecta, particle spectra at approximately 80% of the ejecta height measured from the front of the ejecta were obtained. It was found that when lead is in the solid state (17 GPa), jets consisting of a lot of particles are ejected from the rough surface; when the lead is in the liquid state (34 GPa), a lot of thin (from 7 μ m) microcumulative jets are ejected from the metal surface, and with time they break up into particles.

The experimental data and the results of direct numerical simulation of the flow developed in a constant-cross-section tube in passage of a shock wave through a three-layer gas system are presented. The three-layer systemis formed as a result ofmounting two thin films in the tube and filling the space between them with gases of different densities. The first interface (thin film) makes an angle of 45◦ with the shock front and the second interface is located in parallel to the front. The shock wave is formed at the left tube end and moves towards the first interface at the Mach number M = 2.4. The results of simulation of the problem are compared with the experimental data.

The interaction of a shock wave with turbulent flow was experimentally investigated. The case where a shock wave formed at one end of the tube, passed through the interface between two quiescent gases with different densities (air–CO2 or air–Ar), was reflected from the end of the tube, and interacted with the zone of turbulent mixing formed at the interface. The Mach number of the shock wave incident on the interface in air was M ≈ 2.37–2.57. The flow field was recorded using the schlieren method and high-speed video recording. It was found that after passing the mixing zone, the shock-wave front was deformed and became unstable.

In view of the possible effect of contamination of a plasma by metal particles on the operation of a number of facilities or on the detection of the motion of liners by Doppler methods, a particular attention has been recently focused on the problem of the ejection of particles from the shock-loaded free surface of a sample or on the “dusting” problem. Most information concerns the dusting source associated with the roughness of the surface, manufacturing technology, and the defectiveness and aging of a material. Factors affecting this process such as the profile and amplitude of the pressure on the front of the shock wave arriving at the free surface of the sample, the presence of the gas in front of the free surface, and the pressure in this gas are less studied.

This work presents the results of experimental and numerical studies on the process of turbulent mixing ocurring at the contact boundaries of three-layer gas systems during the passage of a stationary shock wave with a Mach number M ≈ 1.3. The experiments are carried out in an air shock tube. The working gases are air, SF6, and He. The flow structure is recorded by a schlieren method with laser illumination. The data on the nature of turbulent mixing in two-dimensional flows are obtained.

The possibilities of measuring complex Pylenie, which is intended for studying the parameters of the particles ejected from the free surface of a shock-loaded material and was created at the Institute of Experimental Gas Dynamics and Detonation Physics RFNC-VNIIEF, are demonstrated. The operation of the complex is based on the following three methods, which are based on different physical principles and supplement each other: laser-optical method (macro- and microfilming), pulsed X-ray method, and piezoelectric pressure sensors. This complex is used to study the ejection of particles from the free surface of lead samples when a shock wave with a pressure of 7, 16, and 23 GPa at its front reaches this surface. The effect of the surface roughness and the pressure amplitude at the shock wave front on the quantitative characteristics of the process is shown. The calculation-theoretical simulation is performed by two-dimensional numerical calculations of gasdynamic flows, and the calculation results are used to estimate the “ejecta” characteristics in terms of the developed phenomenological model of the process.

The compression of a planar heated gas layer by a moving liquid layer and the effect of turbulent mixing at the liquid-gas interface on the character of gas compression were experimentally studied. The gas compression by the liquid layer in the deceleration stage is accompanied by development of the Rayleigh-Taylor instability and the turbulent mixing (TM). The liquid fragmentation in the TM zone leads to a sharp increase in the heat transfer from hot gas to liquid. As a result, the gas compression dynamics significantly differs, both quantitatively and qualitatively, from that observed in the case of a solid piston. The dynamics of a liquid layer featuring the TM was compared to that of an analogous layer in the case when the TM development was fully suppressed by increased layer strength. The level of the gas compression by the liquid layer exceeded (by a factor of up to ∼1.5) the compression achieved with a solid piston.

The results of experiments with a friable medium layer driven by a compressed gas flow are reported. A layer of polypropylene particles was accelerated in a square channel under the action of air pressure. The initial perturbation on the unstable layer boundary had a nearly sinusoidal shape. Since the medium possesses no tensile strength (and exhibits no surface tension), the unbound particles occurring in the protruding front regions (spikes) of the unstable layer boundary fall into the gas. In the depressed front regions (bubbles), the medium probably exhibits a certain densification and the resulting compressive strength hinders the bubble growth in the initial stage of instability development. The gas penetrating into the layer leads to expansion and fluidization of the layer.