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Features of the simulation of the thermodynamic and gasdynamic processes occurring in devices for reducing the noise level of a shot from a gun were considered. A simulation of large vortices in the nonstationary turbulent flow of powder gases in a muzzle noise reduction device with a silencer representing a shaped channel with several chambers, whose volumes decrease in the direction to the silencer outlet, has been performed. Results of qualitative and quantitative investigations of the initiation, development, and damping of the shock waves in the flow of powder gases, formed as a result of the firing of a shot made from a signal gun, are presented.

Problems on the development of mathematical models for control of the technological processes of producing powders of metals from their melts and for optimization of these processes were considered. A numerical simulation of the solidification of melt droplets in a turbulent cold-gas jet has been performed with the use of a complex mathematical model, and results of this simulation were used for estimating the influence of different factors on the flying of a melt droplet in a gas flow until it is solidified.

In high-pressure gas–jet Hartmann generators, the source of acoustic energy is kinetic energy of a gas jet by the supercritical ratio between the operation and ambient pressure. Under certain conditions, onflow of a supersonic jet to a resonator is accompanied by powerful self-sustained oscillations with irradiation of acoustic waves into the environment and resonator cavity. A model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow. The physical pattern of the flow in the gas–jet generator has been discussed and the study of the dependence of the self-sustained oscillation characteristics on the key gas-dynamic and geometric parameters has been performed.

The gasdynamic processes accompanying the injection of a pulsed gas jet into the diffuser part of a nozzle are considered in relation to the formation of control forces in rocket engines. The gas flow through the injection nozzle is controlled by a rotary damper. The finite volume method and moving mesh technology are used to discretize the Reynolds-averaged Navier–Stokes equations and the equations of the SST turbulence model. The effect of the opening time of the damper on the dynamics of the formation of the control force, as well as the dependence of the traction and energy characteristics of the nozzle on the flow rate of the injected working fluid, are studied. The results of calculations within the non-steady-state and quasi-steady-state problem statement are compared. The formation of the shock wave and vortex structure of the flow is discussed. Conclusions are drawn about the effect of the input parameters of the problem on the coefficient of the traction change.

The numerical simulation of gas-dynamic processes accompanying the transverse injection of a gas jet into the supersonic part of a nozzle is considered in the context of creating steering forces in rocket engines. Numerical calculations are conducted based on various turbulence models at different mass flow rates of the injected gas. The calculation results obtained for the non-viscous, laminar, and turbulent formulation of the problem are compared with each other and with the physical experiment data. The formation of a shock wave and vortex flow pattern is discussed. Conclusions about the effect of problem input parameters on the thrust gain coefficient are made.

The interaction of solid particles with vortex structures was investigated, and the scattering of such particles by a combined vortex was numerically simulated using the Euler–Lagrange approach. The concentration distributions of particles in the region of a gas flow occupied by a vortex at different instants of time have been obtained. The dependence of the time for which these particles escape from the central zone of the vortex on their size was determined. The results obtained can be used for increasing the efficiency of measurement of the parameters of the disperse phase in a fluid flow by optical methods.

According to the experimental study on Vietnamese pigs after implantation of a polypropylene mesh with PRF membrane into retromuscular space, the results of ultrastructural changes in the cells of muscular aponeurotic layer of abdominal wall were presented. It was proved that on the 14th day of the experiment, inflammatory changes in tissues were expressed significantly less than in cases of the isolated implantation of the polypropylene mesh without PRF membrane. Activation of fibroblasts and signs of fiber structures development around the mesh material increased. In the late experimental period (28 days), at the microscopic and electron-microscopic levels the minor manifestations of inflammatory reaction, improved microcirculation in the area of implantation of the mesh with PRF membrane were found that in turn contributed to the increased activity of fibroblasts and development of collagen fibers around the mesh material. The use of PRF plasma membranes stimulated an active development of new capillaries, improved blood flow, accelerated metabolic processes in tissues, and suddenly increased development of collagen, hyaluronic acid that in turn created favourable environment for a complete integration of the polypropylene mesh into the muscular aponeurotic layer of anterior abdominal wall tissue.

The ultrastructural changes of the tissues of musculo-aponeurotic layer of anterior abdominal wall after implantation of the “lightweight” and “heavyweight” polypropylene meshes into the retrometallic space were studied in the experiment. Significant differences of the tissue reactions at different periods of the experiment on the implanted material were evidenced. The presence of a moderately pronounced inflammatory tissue reaction was noticed on the 14th day of the study in the area of the implantation of the “lightweight” polypropylene mesh compared to the “heavyweight” one: the inflammatory response included acute manifestations of aseptic inflammation with a significant tissue response. On the 28th day of the experiment, in cases of implantation of the “lightweight” mesh, the stabilization of tissue reaction to the implant with reduction of inflammatory changes was observed, as evidenced by a significantly smaller number of leukocyte infiltration sites, a significant improvement in vascularization and development of collagen fibres around the mesh material with fibroblasts, which was not observed in the area of implantation of the “heavyweight” polypropylene mesh. The conducted morphological and ultrastructural studies have prioritized the use of “lightweight” meshes when choosing material to perform allohernioplasty.

The formation of regions with a higher concentration of solid particles in the completely developed turbulent flow in a channel with impermeable walls was investigated. A gas flow was simulated on the basis of nonstationary three-dimensional Navier–Stokes equations. The discrete-trajectory approach was used for simulation of the movement of particles. On the basis of the data of a direct numerical simulation, the distributions of the average and pulsating characteristics of the flow in the channel and the concentration distribution of the dispersed phase in it were determined. It was established that the formation of regions with a higher concentration of solid particles in the channel is due to the instantaneous redistribution of vorticity near its walls. The numerical-simulation data obtained are in qualitative and quantitative agreement with the corresponding results of physical and computational experiments.

A numerical simulation of a supersonic two-dimensional gas flow into which a gas jet is injected from the surface of a fl at plate along the normal to it has been performed. The calculations were carried out using the Reynolds-averaged Navier–Stokes equations closed by the SST model of turbulence. The influence of the pressure ratio of the jet on the structure of the flow formed as a result of its injection into the supersonic crossflow, the angle of inclination of the head shock wave, the length of the separation zone, and the depth of penetration of the jet into the main flow were determined. The results of calculations performed for different Mach numbers of the main flow and different pressure ratios of the injected jet were compared with the corresponding results of a physical experiment. The data obtained can be used for optimization of the mixing of the injected jet with the main supersonic crossflow.

The transverse injection of a pulsed jet into a supersonic flow for thrust vectoring in solid rocket motors is investigated. The gas flow through the injection nozzle is controlled by a piston which performs reciprocating motion. Reynolds-averaged Navier–Stokes equations and the (k–e) turbulence model equations are discretized using the finite volume method and moving grids. The pressure distributions on the plate surface obtained using various approaches to the description of the flow field and difference schemes are compared. The solution obtained for the case of injection of a pulsed jet is compared with the solution for the case where a valve prevents gas flow through the injection nozzle. The dependence of the control force produced by gas injection on time is investigated.

The flow of combustion products containing condensed-phase particles over the recessed vectorable nozzle of a solid-propellant rocket motor was investigated with the use of the Reynolds-averaged Navier–Stokes equations, equations of the k–e model of turbulence, and the Lagrange approach. The fields of flows of combustion products and the mechanical trajectories of condensed-phase particles in the charge channel, the prenozzle space, and the nozzle unit of this motor were calculated for different angles of swing of the nozzle. The formation of vortices in the gas flow in the neighborhood of the downstream cover of the nozzle and their influence on the movement of particles different in size were considered.

Results of formation of a ferromagnetic τ-phase and an antiferromagnetic e-phase in alloys of type Mn54Al43C3 obtained by induction and arc melting and by rapid hardening of the melt are presented. The magnetic hysteresis properties of powders produced by high-power mechanical milling of the synthesized alloys are studied. The optimum temperature conditions for transformation of the e-phase into a ferromagnetic τ-phase are determined for the alloys and for their ultrafine powders. The resulting powders of Mn54Al43C3 have an ultimate specific magnetization σ m = 81 (G · cm3)/g and a coercive force H c = 3 kOe in a magnetic field of 12 kOe.

The production of steel grinding balls is improved by reducing the billet temperature before rolling, reducing the number of balls between the flanges of the quenching drum, and limiting the discharge temperature of the balls from the bunker after self-tempering. The macrostructure of the billet must be improved, and proportional increase in length and speed of the quenching drum is required.

We consider current problems of improving propulsion systems of highly supersonic air-space vehicles. In the first part, we review historic developments and list the landmark scientific papers. Classification of detonation engines is presented with detailed consideration of rotation detonation engines and continuous detonation engines. Experimental results on detonation, which are of particular importance for the design of detonation engines, are discussed. The second part of the paper provides an overview of the development in detonation theory, mathematical modelling, and numerical simulation. We focus on the interference of shock waves with formation of triple points, regular and irregular reflection of shock waves, existence of multiple solutions and the resulting appearance of hysteresis. The relevance and importance of triple shock wave configurations for the development of new types of air intakes and detonation jet engines is demonstrated.

A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.

Using transmission electron microscopy methods the layer by layer analysis of rails differentially quenched in different regimes is carried out on different scale levels. It is shown that the differentiated quenching of rails is accompanied by the formation of morphologically different structure, being produced according to the diffusion mechanism of γ-α transformation and consisting of plate perlite grains, free ferrite grains and grains of ferrite-carbide mixture. The gradient character of the changing of structure, phase composition and dislocation substructure parameters in the surface layer of rails head is established. It is revealed that the interfaces between globular cementite particles-matrix are the most dangerous stress concentrators.

A layer-by-layer analysis of rails bulk-hardened in oil and differentially hardened in a variety of regimes is performed by means of transmission electron microscopy. Quantitative parameters of dislocation substructures and internal stress fields, and their dependences on the distance from the tread contact surface are established. It is shown that the most dangerous stress concentrators are interfaces between globular cementite matrix particles; such interfaces form predominantly in rails subjected to bulk quenching.

Features of the technology used to make rail steel at the EVRAZ ZSMK combine are discussed along with the requirements on the steel’s contents of residual elements. A description is given of the step-by-step introduction of a process for sorting scrap to make rail steel, the sorting being based on the scrap’s content of residual elements. A comparative analysis is made of changes in the technical-economic indices of rail-steel production before and after the introduction of the sorting operation and the reasons for those changes are explained. The cost-effectiveness of the measures that were implemented is also evaluated.

Experimental studies are performed for determining the effect of hot rolling process parameters on structure formation and a set of mechanical properties for R65 type rails made from steel E78KhSF under EVRAZ ZSMK conditions. The effect of processing parameters of the existing production scheme (temperature-time, deformation rate and energy and force parameters) for production of R65 type rails made from steel E78KhSF is studied using a Gleeble System 3800 simulation unit.

Methods of transmission electron microscopy are used for layer-by-layer analysis of rails of the highest quality grade. Quantitative parameters of structure gradients, phase composition, and dislocation substructures formed by various mechanisms of γ–α transformation are determined. Sources of long-range stress fields are revealed. It is determined that possible places of microcrack origin in the steel are interfaces cementite particles – matrix.

A layer by layer analysis of rails, differentially hardened in various modes, has been carried out using transmission electron microscopy on various scale levels. It has been shown that the differential hardening of rails is accompanied by the formation of a morphologically different structure, which is formed according to the diffusion mechanism of γ-α transformation and consisting of plate perlite grains, free ferrite grains, and grains of a ferrite-carbide mixture. The gradient character of modifications of structure, phase composition, and dislocation substructure parameters along the cross section of rail head has been established. It has been revealed that the interfaces between globular cementite particles and the matrix are the most dangerous stress concentrators.

The layer-by-layer analysis of the rails classes such as the low-temperature reliability, increased wear resistance, and contact-fatigue strength rails of the superior category of quality after the bulk hardening and tempering and differentially hardening in different regimes is carried out by methods of transmission electron diffraction microscopy of thin foils in the layers located on the roller surface and at the distance of 2 and 10 mm from it on the central axis and on the round corner. The quantitative parameters of dislocation substructure, internal stress fields, structural and phase states formed by diffusion and shear mechanisms of γ−α-transformation are established. The polycrystalline structure is formed in the surface layer of 10 mm thick, independently of the regime of hardening and rail category. The polycrystalline structure is presented by the pearlite grains of lamellar morphology, the ferrite grains, in the bulk of which one can observe the cementite particles of different shapes, and the grains of structurally free ferrite. The relative content of a given type of structure, depending on the hardening regime, rail category, and the depth of location of the layers, are studied. The main structural type of rail steel is pearlite of lamellar morphology with relative content changing in the range from 34% to 87%. Relative fraction of grains of ferrite–carbide mixture is slightly smaller (from 12% to 65% of steel structure). Relative volume fraction of grains of structurally free ferrite is small and is changed in the range from 1% to 5% of steel structure. Dispersion of pearlite structure is estimated, according to the value of interplate distance. As shown, the value of interplate distance is changed in the range from 105 nm to 200 nm. It depends on the regime of hardening, rail category, and distance to roller surface. The evaluation of rail strengthening mechanisms qualitatively being agreed with the hardness measurements is made. As established, the stress concentrator density reaches the maximum value at the tread contact surface. It is higher for the bulk-hardened rails than for differentially-hardened ones. As established, the ferrite component of steel structure is faulty. The dislocation substructures are revealed in the form of chaotically distributed dislocations, nets, cells, and fragments. In the ferrite of pearlite grains, only the first two types of dislocation substructure (namely, substructure of dislocation chaos and netlike dislocation substructure) are observed. The cellular and fragmentary dislocation substructures are revealed only in grains of structurally free ferrite and grains of ferrite–carbide mixture. Scalar dislocation density in ferrite component of rail structure under study is changed in the wide range from 2⋅10^10 cm^2 to 8⋅10^10 cm^2. By analysing the bend extinction contours, the sources of the internal-stress field concentrators are revealed. The most dangerous stress concentrators, which are predominantly formed in the rails subjected to the bulk hardening, are the ‘globular cementite particles–matrix’ interfaces.

Transmission electron microscopy permits quantitative analysis of how the phase composition and defect substructure in the surface layer of rail steel consisting of plate pearlite and martensite nanozones evolve under fatigue. The fatigue failure of rail steel with different structures is discussed.

A turbulent flow of a suspension of solid particles in a gas is considered. The suspension is located in a channel with permeable walls (the pressure at the left end face of the channel follows a sinusoidal law). The flow considered here reflects the principal features of the flow in the combustion chamber of a solid-propellant rocket motor. The unsteady flow of the gas suspension is described by using the Eulerian-Lagrangian approach. A stochastic variant of the discrete-trajectory approach is used for modeling the particle motion. The influence of the condensed phase on the turbulence characteristics and acoustic oscillations of the parameters of the working medium in the channel in the case of injection is discussed. The calculated results are compared with data obtained in a physical experiment.

РЕЗЮМЕ. Досліджено структурну організацію компонентів інтактної рогівки свині та морфологічні структурикріоконсервованої рогівки без кріопротектора ікріоконсервованої рогівки з кріопротектором. Встановлено, щокріоконсервування ксенорогівки після проведення попередньої обробки в гліцерин-жовтковій суміші забезпечуєвисоку збереженість всіх її структурних компонентів.КЛЮЧОВІ СЛОВА: рогівка, структура, кріоконсервування.

Experimental data are presented regarding the differential quenching of rails in air and the properties of the first batch of differentially quenched rail (length 100 m) subjected to certification tests. The prospects for the new class of rails are assessed.

Numerical simulation of turbulent flows of a gas suspension in the vicinity of the critical point and in a channel with permeable walls has been carried out. The influence of the concentration of the dispersed phase and the size of its particles on the distribution of mean and pulsation characteristics of the flow, as well as on the friction and heat transfer coefficients, is discussed.

The motion and heat and mass transfer of particles of a disperse admixture in nonisothermal jets of a gas and a low-temperature plasma are simulated with allowance for the migration mechanism of particle motion actuated by the turbophoresis force and the influence of turbulent fluctuations of the jet flow velocity on heat and mass transfer of the particle. The temperature distribution inside the particle at each time step is found by solving the equation of unsteady heat conduction. The laws of scattering of the admixture and the laws of melting and evaporation of an individual particle are studied, depending on the injection velocity and on the method of particle insertion into the jet flow. The calculated results are compared with data obtained with ignored influence of turbulent fluctuations on the motion and heat and mass transfer of the disperse phase.

The influence of the chemical reactions occurring in the gas phase of a gas suspension flowing in a channel with penetrable walls and the combustion of the condensed-impurity particles in this flow on its gasdynamic structure has been investigated. It is shown that the order of the system of equations defining a flow of a chemically reactive gas suspension with a homogeneous exothermic reaction proceeding at a definite rate and a heterogeneous combustion of the condensed-phase particles can be decreased if certain assumptions are mode. The distributions of the parameters of the gas and dispersed phases were calculated as functions of the rate of blow and the sizes of the particles.

Velocity and concentration distributions of the condensed phase have been obtained based on the parameter-expansion method. The characteristics of two-phase flows in channels with strong and weak injections have been investigated. The factors exerting an influence on the velocity of nonequilibrium phase motion have been determined; the range of applicability of the solution obtained has been established and its qualitative behavior has been elucidated; the possibility of applying such a solution to calculation of the concentration of the condensed phase has been shown.

The effect of longitudinal pressure gradient and localized injection on turbulent heat transfer on a flat plate is treated. The variation of the flow pattern, characteristics of heat transfer, and the efficiency of cooling the plate are investigated depending on the magnitude and sign of the pressure gradient and on the parameters of injection. The calculation results obtained using different models of turbulence are compared with data of physical experiment and available correlations.

On the basis of the thermal approach, a mathematical model of the optical breakdown on condensed inclusions exposed to pulsed laser radiation is developed. As individual stages of the process, we consider the particle heating and evaporation, the formation of a vapor aureole and its ionization, as well as the propagation of shock waves in the space surrounding the particle. The threshold characteristics of the laser-beam parameters sufficient for initiating an optical breakdown on metal and dielectric particles, as well as on dielectric liquid drops are determined.

A mathematical model is developed of optical breakdown on droplets of dielectric liquid under the effect of pulsed laser radiation. The heating and evaporation of a particle, and the generation of a vapor halo and its ionization, as well as the propagation of shock waves in the space surrounding the particle, are treated as separate stages of the process. The threshold characteristics of the laser beam parameters are determined, which are sufficient for the initiation of optical breakdown on droplets of dielectric liquid. The dependence of the threshold power of optical breakdown on the size of laser spot is calculated.

Models of the process of interaction of pulsed laser radiation with gasdisperse systems are developed. Both individual stages of the process accompanying the interaction of a laser pulse with a gasdisperse system and the dynamics of the state of the system under the conditions of interference of processes of various physical nature are modeled. Generalized dependences allowing prediction of the characteristics of a probing beam are constructed. Boundaries of the region of efficient supply of laser-pulse energy to the system are determined.

This paper considers issues connected with the simulation of the motion and heat exchange of disperse impurity particles in nonisothermal gas and low‐temperature plasma jets under the action of turbulent pulsations of the carrier flow. The influence of the outflow conditions, the initial parameters of the phases, and the conditions of particle injection into a jet flow on the laws of impurity scattering and heat exchange are investigated. The results of the numerical calculations are compared with the data obtained without taking into account the influence of turbulent pulsations on the particle motion.

Differential hardening of rails by compressed air in different regimes is accompanied by formation of morphologically different structure, being formed according to the diffusion mechanism of γ↔α transformation and consisting of grains of lamellar pearlite, free ferrite and grains of ferrite-carbide mixture. By methods of transmission electron microscopy the layer by layer analysis of differentially hardened rails has been carried out, the quantitative parameters of the structure, phase composition and dislocation substructure have been established and their comparison has been made for different regimes of hardening. It has been found that the structure-phase states being formed have gradient character, defined by the hardening regime, direction of study from the surface of rolling and by depth of location of layer under study.

Averaged equations for gas suspension motion and equations of the k-e model of turbulence are reduced to a closed system of ordinary differential equations in the region of impingement of a flow on a body. Numerical simulation of impurity motion and heat exchange between a dust-containing gas flow and a wall in the vicinity of the critical point is carried out. The effect of the discrete component on the pulsation characteristics of turbulence is investigated. Results of calculations of the heat transfer coefficient as a function of the ratio of the heat capacities of the phases and the concentration and size of the impurity particles are presented.