Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2023 number 3

Based on the volume-of-fluid (VOF) multiphase model and the fluid-structure interaction (FSI) model, combined with the overset grid technology of the STAR-CCM+ software, a computational model for the oblique entry of truncated projectiles into water is established. The hydrodynamic characteristics and structural response characteristics of the projectile for various water entry angles are calculated and analyzed, and the evolution law of cavitation is determined. The numerical results are found to be in good agreement with experimental data

The parameters of the plasma generated by an arc discharge in gaseous helium at pressures of 3, 25, and 50 torr are studied experimentally and theoretically. The properties and orphology of synthesized soot are investigated by methods of the X-ray diffraction analysis, thermogravimetry, and transmission electron microscopy. A theoretical model is used to predict the radial distribution of the gas temperature, which is consistent with the results of thermocouple measurements. It is demonstrated that a change in the pressure in the arc discharge alters the residence time of carbon vapor in various temperature regions. This fact ensures different conditions of formation of carbon nanostructures and allows obtaining soot with essentially different structural and physical properties.

The influence of sinusoidal pulsations of the flow rate of the dispersed phase on the flow characteristics of immiscible high-viscosity liquids in a T-shaped microchannel has been studied. The flow regimes in the unperturbed flow and in the flow subjected to external perturbations with different frequencies and amplitudes were visualized. A dimensionless complex is proposed that describes the transition from parallel to plug flow due to external pulsations for a fixed capillarity number of the carrier phase. The application of perturbations to the plug flow regime is found to lead to flow stabilization and to a reduction in the spread of values of the generated plugs at a frequency equal to the natural frequency of plug separation in the unperturbed flow. The average length of the plugs and the spread of its values are shown to increase with decreasing perturbation frequency.

The atomization of metastable superheated water injected into the atmosphere from a convergent-divergent nozzle at a temperature of 240-260 °С was studied experimentally. The dispersion composition of the spray jet has a bimodal character with a predominance of submicron droplets, whose proportion increases with increasing temperature and reaches 80% at the nozzle outlet at a water temperature of 260 °С. The influence of droplet coagulation on the distribution of the proportion of large droplets along the length of the spray jet was estimated.

A numerical and experimental study of the influence of viscous and capillary forces on the characteristics of multiphase flow in the pore doublet model, which is one of the most well-known elementary models of the pore space, has been carried out. The OpenFOAM platform was used for numerical simulation. A multiparametric analysis of the process of oil displacement by various agents in the pore doublet model was carried out with varying values of the wettability of the pore surface, pressure drop, surface tension coefficient, and the ratio of the sizes of the channels of the pore doublet. It is shown that the obtained results of numerical simulation are in good agreement with the experimental data for the pore doublet model in the case of a hydrophobic surface at various values of the capillary number. The physical model of the pore doublet is implemented in a microfluidic chip fabricated using the soft lithography method. The proposed numerical-experimental microfluidic approach makes it possible to carry out a numerical study of two-phase filtration in models of a porous medium corresponding to laboratory studies, as well as to scale the results obtained by the characteristic core sizes.

The paper presents the results of studying the dynamics of a wave signal as it passes through gas-vapor bubble "screens" in a liquid, taking into account heat and mass transfer at the interface in the acoustic approximation. On the basis of numerical calculations using the fast Fourier transform method, wave patterns for pressure impulses are obtained and the influence of various parameters of the state of a liquid with vapor-gas bubbles on the reflection and transmission of acoustic waves through the “curtain” is studied.

Interface dynamics between immiscible liquids with a large difference in viscosities is experimentally studied by varying the frequency and amplitude of oscillations, the relative initial position of the liquids, and the thickness of the working liquid layer. It is shown that with an increase in the amplitude of the interface oscillations, a finger-like instability, which has a local character, manifests itself in a threshold manner on its surface. The found instability of the oscillating boundary is similar to the Suffman-Taylor instability, which develops when a viscous fluid is uniformly displaced from a slot channel (porous medium).

The classical two-dimensional Cauchy-Poisson problem for an ocean modelled as an incompressible fluid with an elastic bottom is considered here. In accordance with the linear theory, the problem is formulated as an initial-value problem for the velocity potential in the fluid region, dilation potential, and rotational potential in the elastic medium below the fluid region. The Laplace transform in time and the Hankel transform in space are used in the mathematical analysis to obtain the form of the free surface depression and ocean bed vertical displacement component in terms of multiple infinite integrals. These integrals are evaluated asymptotically by the method of steepest descent. Variation of the ratio of the ocean bed amplitude to the free surface amplitude for different forms of the prescribed initial axially symmetric surface depression or the impulse for different values of elasticity parameters is investigated. The results obtained in the study are compared to the analytical solution of the problem in the case with a rigid bottom.

DNS and RANS computation results for flows in two-dimensional channels with bumps are processed to generate input and output data for a machine learning method aimed to enhance the Reynolds stress anisotropy model and, thus, improve the RANS approach accuracy. The tensor basis random forest method is chosen as a machine learning tool. The prediction of the new model for the Reynolds stress anisotropy tensor is in better agreement with DNS data for two channel flow geometries than those obtained by the conventional linear eddy viscosity model.

The two-dimensional problem of potential flow around two circular cylinders is considered for given velocity at infinity, circulations around cylinders, and the radii and relative position of the cylinders. Exact analytical formulas for the complex potential and the complex conjugate velocities in terms of the Jacobi theta functions are derived. The circulations around the cylinders are uniquely determined using the Gol'dshtik's minimax principle: the circulations should be selected so that the maximum fluid velocity in the stream is minimal.

The propagation and destruction of nonlinear internal waves in the summer-autumn period at the hydrophysical test site of the Pacific Oceanological Institute, FEB RAS in the shelf zone of the Sea of Japan have been studied for a number of years. By continuous measurement of vertical temperature and velocity distribution at depths of 20-60 m using bottom stations and by a regular study of the distributions of the main hydrodynamic characteristics along selected paths, mechanisms have been determined for the generation and propagation of nonlinear packets of internal waves due to internal tide decay and other short-period sources of thermocline deformation have been detected that can be attributed to the propagation of benthic and surface vortex structures. High spatiotemporal resolution of the temperature field in the neighborhood of bottom stations made it possible to reveal the fine structure of wave perturbations of various types. Multilayer shallow-water models for wave-packet propagation have been developed and verified using the data of full-scale and laboratory experiments.

The processes of reflection and refraction of a pressure wave as it passes through the boundary of a bubble medium - pure liquid at an oblique incidence of the wave on the interface between the media are considered. The case was studied when the gas inside the bubbles is explosive. A significant decrease in the amplitude of the initial wave capable of initiating detonation in a bubbly liquid due to wave interference at an inclined boundary has been established.

Data on the parameters of explosion and detonation of two- and three-fuel mixtures of methane, coal dust, and hydrogen (with oxygen and air) with varied fractions of the fuels are reported. The novelty of the numerical and graphical arrays is due to previously unknown data on the kinetic energy of detonation initiation, characteristic size of detonation cells, detonation velocity, and energy release in detonation waves. The analysis is performed not only for stoichiometric two- and three-fuel systems, but also for rich and lean systems based on the fuels under study.

The processes of attenuation and suppression of detonation in gas suspensions of aluminum particles by extended clouds of inert particles are studied on the basis of numerical simulations of two-dimensional flows. The normalized detonation velocity is found as a function of the concentration of inert particles. The conditions of detonation failure are determined for non-stoichiometric mixtures with oxygen and for the case with concentration gradients across the channel. It is demonstrated that a one-dimensional approach has certain limitations in determining the detonation failure criteria because transverse waves of cellular detonation favor its reinitiation. Sufficient conditions of detonation suppression for 1µm particles are determined.

An experimental study of the effect of additives of trifluoroiodomethane (CF₃I) - one of the most effective combustion inhibitors that are safe for both humans and the environment - on the shock-initiated ignition in multicomponent combustible mixtures, namely syngas (mixture of hydrogen, CO, and methane) and mine gas (mixture of methane and acetylene). The addition of CF₃I strongly inhibits the ignition of syngas and affects the ignition of mine gas only slightly. Kinetic modeling has been carried out, and a kinetic mechanism describing the observed regularities has been proposed.

It has been experimentally shown that the flameless combustion of RDX mixtures with iron precursors, nitrogen-containing additives, and a polymer binder can lead to the formation of iron nitrides. Nanosized particles of iron nitride (Fe₃N) were obtained by optimizing the ratio of initial components and conditions of flameless combustion of RDX. The developed method for obtaining iron nitrides can be used to obtain nanosized particles of nitrides of other elements.

The effect of pulsed laser radiation (1064 nm, 120 μs, 10 Hz, 1.5 J/cm²) on coal samples in argon is under study. Mass spectrometry is used to analyze the gaseous products of coal pyrolysis. The dependences of the composition of gaseous pyrolysis products of coal samples and the proportion of reacted samples on their technical and genetic characteristics are established. Data on the yield of combustible gases per unit mass of reacted coal samples were obtained.

For the first time, a comparative study of the combustion of powder and granular mixtures Ti + C, (Ti + C) + 20% Cu with granules of different sizes with varying the particle size of titanium from 31 to 142 μm was performed. It has been found that the combustion rate of the (Ti + C) + 20% Cu powder mixture is higher than that of the Ti + C mixture, despite the lower combustion temperature. The use of the “gasless” combustion theory to determine the kinetic parameters of the process from the burning rate of the powder mixture leads to a negative value of the apparent activation energy, which shows the inapplicability of the traditional approach. The results are explained within the framework of the convective-conductive model of combustion by the retarding effect of impurity gases released during heating of component particles ahead of the combustion front. Using the values of the burning rate of granular mixtures with granules 0.6÷1.7 mm, the burning rate of the substance of the granules is calculated, i.e. the burning rate of the powder mixture, in which the influence of impurity gases is leveled. The ratio of the burning rates of a substance inside granules and powder samples determines the measure of the influence of impurity gas evolution on the burning rate of a powder mixture.

The effect of mechanical activation of components and external pressure on the combustion of a heterogeneous Ti + C mixture under SHS compaction conditions has been studied. It is shown that when burning under pressure (15 MPa), a low-speed layered regime (4÷7 cm/s) is realized, without external pressure - non-stationary high-speed combustion modes (50÷70 cm/s): surface-annular and volumetric, carried out due to convective heat and mass transfer. A mechanism for high-speed convective combustion is proposed, based on the ignition of a heterogeneous mixture by a hot impurity gas released in the combustion wave and filtering through layered cracks and other macrodefects in the volume of charge compacts that were formed during the pressing of powder mixtures. Mechanical activation of the components of the reaction mixture reduces the density and strength of the compacts and increases the efficiency of the formation of macrodefects. External pressure has the opposite effect, as it prevents the formation of cracks and the propagation of hot impurity gas through them. Consolidated samples of titanium carbide up to a relative density of 95% were obtained in the bulk combustion mode.

This paper presents a study of the dependence of the acoustic emission parameters recorded during quasi-static compression and the shock-wave sensitivity characteristics of parts made of plastic-bonded HMX on the filler particle size. The dependence of the acoustic emission parameters on the HMX particle size was used to describe the possible variants of degradation of the explosive structure under shock-wave loading, which are considered as the cause of the difference in shock wave sensitivity.

To develop a green primary explosive, we prepare an Al@KIO₄ nano-thermite using spray co-precipitation and then mix it with pentaerythritol tetranitrate (PETN) to form a PETN/Al@KIO₄ composite as a primary explosive. The thermite structure is characterized using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy, which indicates that the thermite is about 200 nm and well distributed. The combustion performance is investigated using high-speed photography and confined combustion experiments. The results show that the detonation time of PETN/Al@KIO₄ composites is 60 μs earlier than that of pure PETN, indicating that the thermite accelerates the process of the deflagration-to-detonation transition of PETN. The detonation performance of the composites is investigated, and it is verified that PETN/Al@KIO₄ can initiate RDX successfully and be used as a primary explosive. Moreover, the safety performance and long-term storage performance of the composite are evaluated, which shows that the PETN/Al@KIO₄ composite performance is steady and the initiation effect does not change after 20 years of storage.

In this paper, the behind-plate overpressure caused by a polytetrafluoroethylene/aluminum/tungsten (PTFE/Al/W) reactive fragment is theoretically and experimentally analyzed. The theoretical energy of the PTFE/Al/W reactive materials is calculated by analyzing the chemical reaction of these compositions. Furthermore, based on the one-dimensional shock wave theory and the energy release behavior of the reactive fragment, an analytical model of the behind-plate overpressure is developed. By using binary quadratic polynomial fitting, a polynomial expression of the mass loss of the initiated reactive materials is derived based on the experimental data. The results show that the theoretical analysis model can be used for the estimating the overpressure when a reactive fragment impacts an aluminum plate within experimental conditions.

In the development of specialized explosion-proof chambers subject to increased requirements for strength reliability, an important issue is the choice of the material of the power block subjected to pulsed (dynamic and shock-wave) loads. As a rule, such structures are manufactured from industrial pipes of low alloy steel of various standard sizes. This always involves the question of choosing the steel grade, especially at the stage of computational justification of their explosion resistance, since the dynamic strength characteristics of the pipe material is generally unknown. This paper presents for the first time the results of a study of the static, dynamic, and shock-wave compressive and tensile strengths of 17G1S, 09G2S, and 10G2FBYu pipe steel of K60 strength class. In addition, comparative data on the explosion resistance at strain rates of (2÷5) ·10² c^-1 of pipes from 09G2S and 10G2FBYu steels.

The author studies stress concentration in wellbore zones during operation of underground gas storages. Numerical modeling yields that at the early stage of high-pressure injection of gas in underground gas storages, near the roof of a productive stratum, in rocks and in the cement lining, destructive shearing stresses arise, comparable with the injection pressure, which can induce the loss of tightness in the annular space. For preventing the loss of gas, it is proposed to ream the wells in the roof of a productive stratum and to install a spring centralizer at a certain place in the casing string. The nominal diameter of the centralizer should exceed the wellbore diameter. This can stop propagation of cement destruction. For decreasing the destructive stress intensity, it is advisable to round off corner zones while reaming within the interval of a productive strata.

Physical modeling of hydraulic fracturing is carried out in cubic blocks with an edge length of 200 mm, made of sand concrete mixed with coal fraction, in the nonuniform stress field. A fracture was created in a vertical branched hole. Computer tomography enabled studying the stress raiser at the mother and daughter hole juncture, the actual diameter of the borehole, the drilling-induced fracturing, the sizes of pores formed in consolidation of the manmade blocks, and the trajectories of the created fractures. It is found how the problem geometry and the compressive stresses affect the direction of the created fracture growth.

A series of laboratory pull-out tests were performed on several types of bolts to investigate the effect of profile geometry of resin grouted bolts on load transfer mechanism. Therefore, three different types of bolts were used to prepare twelve series of specimens with different profiles. To evaluate the effect of bond length, the specimens were made using rebar bolts with two embedment lengths of 75 mm and 150 mm. The results showed that load transfer capacity and displacement at peak load were effectively related to the profile configuration and annulus thickness of resin. The bolt types T1 and G2 had higher peak share stress levels and the bolts with a rib spacing of 12.5, 16, 25 and 8 mm had the highest peak shear strength, respectively. By decreasing the rib spacing and embedment length, the system stiffness increased. In the bolt types T1 and G2, by increasing the embedment length from 75 mm to 150 mm, the shear stress decreased by 7.8% and 10.5% and their stiffness decreased by 60.8% and 75.6%, respectively. As the thickness of the resin annulus increased, the peak load decreased.

This article presents an artificial neural network (ANN)-based mathematical model for the prediction of the intensity of ground vibration at the Veliki Krivelj copper mine. The starting points for the development of the model are the model of ground vibration, the software package Peltarion Synapse, as a basis, using artificial neural networks ANN and input-output data set of blasted patterns at the Veliki Krivelj open pit. The input-output set contains the values of the blasting parameters of individual blasting patterns and the measured peak particle velocities when blasting those patterns. The advantage of the ANN method was confirmed by comparing the results of predicting the particle velocity obtained by different methods.

The behavior of a pillar is examined in the course of mining of a blind ore body in the Southeast site of Tashtagol field. The geomechanics and geodynamics of the field is analyzed. The article gives calculations of stresses and inelastic strains, as well as the possible failure zones nearby the mined-out space during actual mining in the Southeast site and in the period of ground surface sink. The authors present the geophysical survey data on the thickness of the crown pillar between the mined-out area roof and ground surface. The area and parameters of the sink are determined from gravimetric measurements and aerial photography.

The article describes the integrated analytical studies and geotechnical assaying of blasted ore samples with size classification at a gold deposit. The parameters of mixed fractions for processing using different technologies are determined. The ore mining and processing flowsheet is developed for a structurally complex extraction block. An improved technology is proposed for the structurally complex ore deposit. Selective ore extraction is followed with screening and size classification into fractions with high and low contents of useful component. The fractions are blended, the blend with the high content of useful component is subjected to flotation, and the blend with the low content of useful component goes to heap leaching. The fraction with the increased content of useful component from rich ore is treated by two-stage sorption and leaching pre-oxidation, which ensures high metal recovery.

The present article describes the extensive characterization and stabilization of concentrated iron ore suspension having size ≤ 75 µm by various bench-scale tests. The rheological characteristics of iron ore in the concentration range of 60-80% (by wt.) have been investigated with and without the addition of Sapindus Mmukorossi dispersant. The stability of iron ore suspension with saponin is established through rheological properties, dispersant concentration and stabilization mechanism. The nature of experimental rheological data at different shear rates is accomplished by regression analysis and found to be a good fit with Herschel-Bulkley model. The Critical Micellar Concentration of the aqueous extracted dispersant is 0.018 g/cc. The presence of Sapindus Mukorossi saponin greatly improved the slurryability and stability of iron ore suspension. The head loss and specific energy consumption analysis successfully evidence the economic relevance of the surfactants in transporting the slurry through the pipelines.

Crushed rock shear tests are carried out to determine stability of a tailings pond dam. The tests allow finding the rock strength at different grain composition and density of rocks, as well as at different shear ring diameters and normal pressures. It is found that the internal friction angle and cohesion range as 35-40° and 0.0256-0.0293 MPa, respectively, in compacted rocks, and as 25-30° and 0.0163-0.0184 MPa, respectively, in uncompacted rocks.

The authors present the formulation and solution of a problem on the efficient engineering data of multi-drive high-duty belts for bulk coal. The theoretical framework for calculating the belt thrust includes the main equation of the belt conveyor dynamics, and features of calculations in stationary mode and in starting conditions with the regard to horizontal and vertical curvature of the belt route. The rational width and production capacity of a belt conveyor are substantiated. The hauling power and capacity of drives of a multi-drive belt are calculated. The strength test of a selected belt is performed. The calculation using the developed program LENTA 1.0 is presented as a case-study of a multi-drive belt conveyor in Inaglinskaya Mine in the South Yakutia coal field.

The structural layouts of pneumatic percussion machines are reviewed. The use of a pneumatic percussion machines with mixed-type air distribution via elastic valve is substantiated for implementation of adaptive technologies. The authors present the theoretical and experimental studies into dynamics of duty cycle of a pneumatic percussion tool with on-line power adjustability.

A brief literature review on flotation of calcium-bearing minerals is given. It is found that flotation activity of a collector is connected with physisorption of the collector in particle-bubble attachment. The tests prove that physisorption decrease reduces recovery and increases the useful component content /yield ratio in the concentrate. The found correlation is a framework for new approaches to quality improvement of flotation concentrates. The method proposed to select compositions of collectors can enhance selectivity of extraction of useful minerals.

The authors have correlated the fluorescence spectrum with the spectrum and kinetics of X-ray luminescence of organic collectors. The correlations prove applicability of organic collectors with modifying agents. From the integrated evaluation of organic liquids by the criteria of their adhesion capacity relative to diamonds and extraction capacity relative to inorganic luminophores, the selected organic collectors are: diesel, heavy gasoil of catalytic cracking, and their mixture. The spectral functions of organic luminophores contained in organic collectors are replaceable with polyaromatic hydrocarbons which generate intense signals similar to the signals of organic luminophores. Efficiency of modifying agents containing organic collectors and hydrophobic luminophores E-515-115-G5 and FL-530-GZ is high. The test organic collector was heavy gas oil of catalytic cracking and diesel fraction at a ratio of 61-9:1. Recovery of weakly and abnormally fluorescent diamonds was 80-90%, while recovery of kimberlite was not higher than 1%. The results allow recommending the developed modifying agents for the commercial-scale X-ray luminescence separation of diamond-bearing materials.

The article proves the promising nature of using functionalized magnetic nano particles in extraction of metals from process solutions and in treatment of industrial effluents. The experimental copper extraction from solutions using a magnetic nanosorbent made of lipoic acid-functionalized magnetite is described. Sorption efficiency is determined as function of the initial concentration of solutions as compared with non-functionalized nano-size magnetite. The copper-bearing sedimentation mechanism includes chemosorption at active centers of lipoic acid, adsorption at clean magnetite surface and re-crystallization of sorbate in intrinsic copper-bearing phases. The phase composition of copper in the sediments is examined, and the copper extractability is illustrated. The conditioning technology is proposed for copper-bearing solutions. The stage-wise use of the magnetic nanosorbent enables process solution purification up to the maximum allowable concentration at simultaneous production of a concentrate suitable for hydrometallurgical processing.

The test of gold-bearing humic substances aimed to find forms of gold in them. The test results enable estimation of gold compound mobility during sedimentation of humic acids. Re-sedimentation of humic acids shows similar properties of gold after dissolving with and without a selective dissolver. The amino-acid analysis of humic acids before and after their interaction with ammonium hydroxide reveals the increased content of amino acids capable to dissolve gold. Stage-wise spin of gold-bearing liquid humic acids at acceleration from 4000g to 233000g and at pH of 11 nullifies gold-bearing particles in solutions and makes the latter homogenous. The authors describe the impact of destructive effects relative to organic compounds on joint sedimentation of gold and humic acids.

The post-leaching of silver (Ag) from a non-sulfide lead-zinc (Pb-Zn) ore flotation tailing leach residue in a copper-ammonium thiosulfate solution was investigated. Ag (89.7%) was extracted into the leaching solution under the following conditions: 30 g/l ammonium thiosulfate, 0.5 g/l copper sulfate, 25°C leaching temperature and 4 h leaching time. On the basis of the experimental results, a fuzzy logic prediction was made. Ammonium thiosulfate, copper sulfate and leaching period were chosen as predictive criteria in this step. The fuzzy prediction model was found to be very consistent with the experimental data (R²:0.9657). Based on these findings, the application of the fuzzy logic prediction approach to the silver dissolution from the leach residue could be considered.

The authors discuss concentration of chemical elements in underspoil water subject to a season and to climatic conditions. The features of underspoil water composition are analyzed with respect to chemical composition of spoil rocks in water and acid extracts. Majority of the test elements correlate well with their composition in the acid extract and with the spoil rocks composition. The water extract is assumed to be unreliable to predict composition of underspoil water.

The article analyzes the impact of water inflow in a mine on the efficiency of the main mine water drainage system as a case-study of Udachny Mine, ALROSA. It is found that the content of solid particles in mine water grows with the increasing water inflow in the mine. A method is proposed to eliminate excessive water inflow in the mine in warm season in case of a pumping station teardown because of the spoil bank slide. The expected payback time of the proposed engineering solution is calculated.