Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2025 number 5

We discuss the results of aerosol studies during high-latitude (81-88.5° N) expedition “North Pole-41” in the Arctic Ocean. The average mass concentrations of black carbon (еВС) in the surface atmospheric layer over 20 months of measurements were 19 ng/m³; volume concentrations of submicron ( V_f ) and coarse ( V_с ) aerosol were 0.41 and 0.65 μm³/cm³, respectively. The average aerosol optical depth of the atmosphere at a wavelength of 0.5 μm and the Ångström exponent in the spring periods of 2023 and 2024 were 0.095 and 1.52, respectively. The seasonal variations in the aerosol and black carbon concentrations were well manifested in high-latitude (near-pole) part of the Arctic Ocean. The concentrations were maximal in spring (еВС = 29 ng/m³, V_f = 0.61 μm³/cm³, V_c = 0.77 μm³/cm³) and minimal in June - October (еВС = 11 ng/m³, V_f = 0.13 μm³/cm³, V_c = 0.26 μm³/cm³). The average aerosol characteristics measured in near-pole zone are several-fold lower than the long-term data in more southern regions of the ocean and at polar stations (Barentsburg and “Cape Baranov”).

The paper presents results of lidar monitoring of the atmosphere over Tomsk in winter 2023/24. The work studies the thermal regime of the middle atmosphere with emphasis on disturbances in the stratosphere caused by sudden stratospheric warmings (SSWs), including statistics on the vertical temperature distribution (VTD) for further analysis. During this period, 90 temperature profiles were calculated from lidar returns of molecular (Rayleigh) and spontaneous Raman scattering in the altitude range from 10 to 70 km. The annual cycle of the vertical temperature distribution is characterized by stratospheric warmings and their destruction in winter and spring, VDT stabilization in warm season, and VTD destabilization in fall with transition to winter SSW phase. In most cases, the vertical temperature distribution in April-October was in good agreement with the model distribution. It has been found that during two stratospheric warming events in winter 2023/24, a splitting of circumpolar vortices occurred at the time of their maximum manifestation (on December 13, 2023, and February 18, 2024). The results are particularly interesting for understanding climate change in Western Siberia.

This work studies spatial distribution of accumulation levels of 21 compounds of polycyclic aromatic hydrocarbons (PAHs) in the snow cover of Baikal Natural Territory in winter 2021/2022. The highest PAHs concentrations were revealed in industrial cities of the Baikal Region (14-3400 μg/m²), and the lowest ones, on the lake ice in Northern Baikal basin (2.0-7.7 μg/m²). The local character of PAHs expansion near source of their emission is revealed. Total PAHs income onto Lake Baikal surface during winter 2021/2022 was 128.8 kg, high values were determined for phenanthrene, fluorantene, pyrene, benzo(b)fluorantene, benzo(k)-fluorantene. The spatial distribution, diagnostic ratios, and factor analysis of PAHs have revealed main sources of air pollution by this class of compounds during a cold year period, i.e. carbon and liquid fuel burning. We assessed the degree of snow cover pollution by coefficients of ecological risk ( RQ ) with a high contribution of benzo(b)fluorantene.

During long-term measurements at two lidar stations of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, pronounced aerosol layers were recorded in the stratosphere over Tomsk on February 5 and 6, 2025. The analysis of lidar and additional meteorological information showed the occurrence of a rather rare phenomenon for middle latitudes, polar stratospheric clouds, at that time. The constructed back trajectories of air masses at the altitudes of the formation of polar stratospheric clouds over Tomsk showed that abnormally cold air masses were brought from the polar regions of Norway and Greenland. The results can be useful for specialists in atmospheric physics, climatology, and environmental protection.

Ozone in the surface air layer in high concentrations is a powerful oxidizer that has a negative impact on biological objects and environmental elements. Therefore, it is very important to study the dynamics of its concentration in all regions of the planet. In the work, based on annual monitoring data, ozone concentrations in Russia in 2024, mesoscale differences in its content in individual regions, and its vertical distribution according to aircraft sounding data are considered; the comparison with hygienic standards is made. It is shown that the average annual ozone content in the surface air layer across Russia varied from 17 to 92 mg/m³; maximum hourly concentrations, from 90 to 222 mg/m³. In the annual course, the maximum concentration is usually observed in spring under background conditions and in summer in urban areas. A secondary maximum became noticeable at background stations in early autumn. The magnitude of mesoscale differences in concentrations reaches 50-70 mg/m³ and changes significantly during the day and year. In most measurement points, the maximum permissible daily average concentrations established by the domestic hygienic standard were exceeded: maximum one-time, daily average, and annual average. The current situation necessitates wide public awareness of the monitoring results and the development of environmental protection measures to reduce the level of ozone and its precursors concentration in the ground layer of air.

Studying the characteristics and dynamics of stratospheric polar vortices requires the correct determination of their edges. Polar vortex delineation methods are mainly based on the values of potential vorticity (PV) or geopotential (GPT). The problem in directly comparing the PV and GPT methods is that the former determines the vortex edge on isentropic surfaces, while the latter does it on isobaric ones. In this paper, we present an algorithm developed to adequately compare the results of polar vortex delineation by these methods. The algorithm is based on projecting the vortex edges onto isopotential surfaces (i.e., surfaces of constant geopotential height), same for both methods. Application of the algorithm to delineating the 2019 Antarctic polar vortex showed, in particular, the following: (1) during the period of the vortex stable state (June 1 - August 31), its area on isopotential surfaces estimated by the GPT method exceeds the area estimated by the PV method by 16.17-21.20 million km² in the range of geopotential heights 20.89-24.37 km, respectively; (2) the dynamics of the vortex edge and area estimated by both methods are generally similar, but the vortex edges obtained by the GPT method are smoother, and the strong irregularity of the vortex edges obtained by the PV method leads to abrupt changes in the vortex area. The algorithm will be useful in studying the dynamics of polar vortices from the beginning of their formation to the moment of breakup in both hemispheres.

The kinetics processes of triplet bands of molecular nitrogen were studied in air at pressures of 0.03-1 Torr. The dependences of the ratios of the spectral density of radiation energy of four bands of the first positive system of nitrogen to two bands of the second positive system of nitrogen are demonstrated. The results of simulation and experimental measurements show an increase in the ratio of the intensities of the bands of the first positive system to the intensities of the second positive system with a decrease in the pressure. It was found that this is due to an increase in the rate of quenching of the B³П_g state by nitrogen molecules with an increase in atmospheric density. These results explain the reason for the change in the color of red sprites with a decrease in the altitude above sea level starting from about 50 km.

Land degradation and increasing deflationary processes make urgent the development of effective methods for monitoring atmospheric and soil processes. The paper describes SAM-V autonomous monitoring system designed at Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch, Russian Academy of Sciences (Tomsk). Its advantages are: domestic software which enables data collection with a preset frequency, variability of configuration, ease of transportation and installation, and high measurement accuracy. The system was installed by scientists of the Federal Research Center of Agroecology, Russian Academy of Sciences, on a local deflation outbreak of 182.6 ha in area in the Republic of Kalmykia. New soil and atmospheric parameters received with this system will be used to analyze aeolian processes in order to scientifically substantiate phytomeliorative measures for the restoration of degraded lands. In the future, it is planned to expand the use of SAM-V system on other scientific objects.

The cavitation process in a pulsed focused ultrasonic field is investigated. For the first time, an abnormally long delay (up to several minutes) in the onset of non-stationary cavitation relative to the moment the ultrasound is switched on has been recorded. A methodology for selecting field parameters that enables control of the dynamics of cavitation region development is proposed.

The characteristics of pressure pulsations on a flat semi-infinite barrier impinged by a supersonic underexpanded jet are investigated. The Mach number at the nozzle exit is M _а = 1, the degree of underexpansion is n = 2,1, and the distance from the nozzle exit to the barrier is h/D_а = 2 ÷ 15 ( D_а is the nozzle exit diameter). It is shown that tangential injection of six microjets can significantly reduce pressure pulsations on the barrier. The mass flow through all microjets is 0,3 % of the mass flow through the main jet. It is established that when h/D_a < 3, a self-oscillatory mass-flow regime of jet-barrier interaction occurs; when 3 < h/D_a < 8, a self-oscillatory regime with acoustic feedback takes place; and when h/D_a > 8, the turbulent aperiodic interaction regime is realized.

The concept of plasma-assisted combustion, which offers several advantages (reduced ignition delay, improved mixing, and stabilization of the flame front), is considered. The paper presents the results of a study of ignition by means of a longitudinal direct-current discharge of a fuel-air mixture injected at supersonic speed into the core of a supersonic airflow. To eliminate the effect of mixing, the fuel (ethylene) was premixed with the oxidizer (air). The design of the ethylene-air mixing system and the injection system of the resulting mixture into the test-section channel is described. For this configuration, results of gas-flow modeling using the FlowVision software package and experimental results on fuel ignition in a supersonic flow are presented.

The processes of wear and failure of VT6 alloy with a ZrN protective coating in the initial coarse-grained and ultrafine-grained states under high-velocity dynamic erosion by corundum particles with average sizes of 109, 58, and 23 μm in an air flow at velocities of 50 ÷ 250 m/s and exposure times of 30, 60, and 300 s are experimentally studied. The experiments determined the fraction of viscous failure, the depth of the damaged layer, changes in the alloy microstructure near the eroded surface with and without coating, as well as weight loss and surface roughness. It is shown that under high-velocity erosion, wear and failure processes of the alloy strongly depend on exposure time, erosion velocity (particle velocity), particle size, and substrate structure.

Using a fiber laser and post-weld heat treatment, high-strength laser-welded joints of an Al-Cu-Li alloy were produced. Synchrotron transmission studies were used to analyze the structural-phase state of the weld seam before and after treatment. Data on the structural and phase composition of the weld seam as a three-dimensional volume were obtained. The influence of heat treatment on the fatigue resistance of Al-Cu-Li alloy laser-welded joints was studied. Static mechanical tests of the laser-welded joints were carried out at normal, elevated, and reduced temperatures to determine the strength and deformation characteristics of the Al-Cu-Li system. Dynamic tests of welded joints of the Al-Cu-Li system under impact bending were performed using the Charpy method.

The mechanism of aluminum (Al) coating formation on a titanium (Ti) substrate during cold gas dynamic spraying was investigated. Structural studies of the coatings obtained by this method showed that they contain a rough transition layer in which Al and Ti atoms are intermixed. It is assumed that the transition layer forms during particle impact with the rough substrate due to a convective mechanism. Numerical modeling of mixing using the smoothed-particle method was performed for the problem of Al microparticle impact on a Ti substrate containing a conical cavity. It was shown that in this case, a cumulative jet of Al is formed, penetrating into the Ti substrate, cooling, crystallizing, and remaining in it as an aluminum inclusion. As a result of numerous microparticle impacts, a transition layer is formed on the substrate with reduced activation energy for bond formation between Al microparticle atoms and Ti atoms of the substrate. The impact of Al microparticles on the transition layer can lead to their adhesion to the surface and the formation of an aluminum coating.

A one-dimensional evolutionary system of equations is proposed, which describes in the Boussinesq approximation the motion of a thin bottom layer in a flooded domain of a lighter fluid, taking into account the development of shear instability and the formation of an intermediate mixing layer. For hydrostatic flows, the propagation velocities of perturbations are determined, and the concept of subcritical (supercritical) flow is formulated. The stationary problem of the mixing layer is considered. It is shown that, depending on the Froude number of the incoming flow, either a monotonic or a wave-type mixing layer is formed. In the first case, a regime of maximum entrainment is achieved, and the stationary solution is determined over a finite interval. When accounting for non-hydrostatic pressure in the lower layer, stationary solutions are constructed in the form of second-mode solitary waves adjacent to a given steady flow. Unsteady calculations of the formation and propagation of large-amplitude bottom waves were performed.

An experimental study was carried out on the interaction of a longitudinal vortex generated by a jet vortex generator with a turbulent boundary layer developing over a flat plate. The main measurements were performed using the PIV method. Based on these data, Reynolds stresses were obtained, and their contribution to the Navier-Stokes equations was investigated. Data analysis allowed the derivation of integral relations characterizing the influence of longitudinal vortex intensity on the turbulent boundary layer. It was found that the action of the jet vortex generator can lead to a reduction of energy dissipation in the turbulent boundary layer.

Results of the implementation and application of adiabatic and isothermal wall boundary conditions with slip and temperature jump in the computational code HyCFS-R for modeling near-continuum flows are presented. Validation was performed on problems with external and internal flows. As an external flow, the flow around a T2-97 cylinder with a skirt was selected; as an internal flow, the propagation of a shock wave in a long tube and the flow in a nozzle at low Reynolds numbers were considered. It was found that, in the case of flow around a cylinder with a skirt, the implementation of the slip boundary condition provides better agreement with experimental data on separation and reattachment points than the no-slip condition. It was shown that, in the calculation with the slip boundary condition, the shock wave propagates along the long tube faster than in the calculation with the no-slip condition. The calculated shock wave propagation velocities are in satisfactory agreement with experimental data. In the case of gas ejection from a nozzle, the use of the slip boundary condition leads to better agreement between the calculated and experimental temperature distributions along the surface.

The structure of upward bubbly flow in an inclined circular tube was studied experimentally. Local gas content profiles were obtained using a point conductivity sensor. Wall shear stress was determined using the electrodiffusion method. It was shown that the orientation of the tube has a significant effect on the local characteristics of gas-liquid flow. In the upper part of the inclined tube, a significant increase in gas phase concentration occurs, leading to higher maximum values of local gas content near the wall and increased wall shear stress compared to single-phase flow. The most significant increase in shear stress occurs at inclination angles from 40° to 60°.

Mathematical models in the long-wave approximation for a three-layer fluid, taking into account mixing and entrainment at the layer interfaces, are considered. These nonlinear models are used to describe changes in the characteristics of heterogeneous flows when passing over localized seabed elevations. Comparison of numerical results with field measurements shows that the models adequately reproduce the structure of shelf and deep-water currents, in which flow splitting occurs with subsequent thickening of the passive intermediate layer and the formation of an intense downslope jet downstream of the obstacle.

Based on a formulated mathematical model, numerical experiments were carried out to study the degradation of permafrost containing ice, accumulations of metastable preserved gas hydrates, and free gas under thermal and saline effects of solutions, taking into account the osmotic effect. Multivariate calculations were used to investigate the patterns and rates of permafrost degradation and methane release. A comparison of some model results with corresponding experimental data showed good agreement.

Based on filtration equations, the problem of CO₂ injection into a viscoelastic porous medium is considered. A two-dimensional problem of deformation of the porous skeleton, taking into account changes in porosity, was studied. For the model system of equations in a thin layer, an exact solution of the initial-boundary value problem was constructed.

The initiation of an inclined edge crack of mixed type (modes I and II failure) in a thin strip of sheet steel under tensile loading is considered. During rolling, an initially isotropic sheet metal typically develops significant anisotropy, characterized by differences in plastic properties along the rolling and transverse directions. The quadratic Hill yield criterion is used to describe plastic anisotropy. The failure process of such materials is described using the modified Leonov-Panasyuk-Dagdale model. Under complex loading, the crack path curves, so the trajectory deflection angle is determined using the force-based integral strength criterion. In the asymptotic representation, stress components near the crack tip account for non-singular terms (T-stresses). To obtain critical failure parameters of a strip with an inclined edge crack, a two-parameter strength criterion is proposed. The parameters in the analytical model are analyzed. Dimensionless geometric parameters of the structure are determined numerically using the finite element method. A system of two nonlinear equations is obtained for the critical length of the pre-failure zone and the critical load under complex stress conditions. Using Hill’s yield criterion, the shape and size of the plastic zone near the crack tip in a plastically anisotropic material are determined.

Results of computations of continuity and stress fields (in the Lagrangian formulation) near the crack front under creep conditions are presented and discussed. Calculations were performed using the finite element method to determine asymptotic distributions of stresses and continuity (damage) near the edge of the cut. For various material constant values, the shape of the damaged material zone under creep developing ahead of the crack tip was determined. Analysis of radial stress distributions obtained from finite element computations shows that the damage accumulation process alters the asymptotic behavior of stresses near the crack tip in a material described by a power-type governing equation. It was shown that, in the absence of damage accumulation, the numerical solution approaches the Hutchinson-Rice-Rosengren asymptotics, whereas accounting for the damage accumulation process affects the stress field near the cut or crack. Using finite-element radial stress and continuity distributions, characteristic sizes of zones dominated by different asymptotics near the crack tip can be determined.

Physical modeling of the forming process of a panel made of AK4-1 (Al-Cu-Mg) alloy under creep conditions at an annealing temperature of T = 420 °C was carried out. The forming process was simulated by tensile creep of cylindrical specimens to various strain values not exceeding 6 %. The tests yielded parameters of the classical Boyle-Norton model for steady-state creep. In accordance with the technological forming process under creep conditions, heat treatment (quenching and aging) was performed to restore the panel’s strength properties. Stress levels for fatigue tests were determined using stepwise cyclic loading with increasing stress amplitude. Tests were stopped upon the occurrence of plastic deformations. A comparison of fatigue resistance characteristics was performed for as-received specimens, specimens stretched under creep, specimens after heat treatment, and specimens with zero creep strain after heat treatment. It was shown that accumulated creep strain exceeding 2 % can reduce the fatigue performance compared to as-received specimens.

The problem of forced bending vibrations of a strip-bar with two cantilevers and a fixed finite-length section on one of the lateral surfaces is addressed. The classical Kirchhoff-Love model is used to describe deformation of the cantilevers, and the fixed section is described by a refined Timoshenko shear model accounting for transverse compression, modified to consider the prescribed displacements of the support element. Kinematic coupling conditions for the fixed section and cantilevers are formulated, and using Hamilton-Ostrogradsky’s principle, equations of motion, boundary conditions, and force coupling conditions for the bar sections are derived. An exact analytical solution is obtained for harmonic forced vibrations under the action of a harmonic transverse force at the end of one cantilever. Numerical experiments were conducted to study forced bending vibrations of a strip-bar made of D16AT duralumin. It was shown that vibrations of the unloaded cantilever are primarily determined by the prescribed displacements of the support element.

Results of studies on the reliability of mathematical modeling of metal plastic flow using the finite element method implemented in various software products are presented. The limitations of the finite element method and their influence on the description of deformation processes occurring during intensive shaping of a workpiece are analyzed. Special attention is paid to the study of regions with complex metal flow. A comparison of mathematical modeling results obtained using MSC Simufact.Forming, Transvalor Forge, SFTC DeForm, and QuantorForm QForm with parameters of actual products is carried out. It is shown that the results of mathematical modeling performed with the mentioned applied software products for complex metal flow studies are sufficiently reliable.

The problem of group classification is solved for equations describing vibrations of a nonlinear elastic plate in a gas flow. Exact solutions of these equations are presented, which can be used as benchmarks for numerical solutions.

This paper presents experimentally obtained shadowgraph images of the shock wave structure in an unsteady supersonic reacting flow of a hydrogen-oxygen mixture, generated by a spherical projectile flying at a velocity exceeding the self-sustained detonation velocity. The conditions for the formation of a stabilized oblique detonation wave, initiated by the high-speed projectile both in free space and in the presence of a wedge surface placed at a certain distance along the projectile trajectory, are determined.

This paper presents a comparative study of the efficacy of fibrous and particulate reinforcement in titanium-matrix composites under high-speed mechanical loading. The structural and phase composition of the synthesized materials is investigated using synchrotron radiation. It is found that, during laser processing, fibrous reinforcing elements dissolve in the titanium matrix to a lesser extent than particulate powder particles. This causes a reduced volume fraction of the resulting secondary phases, such as TiC and Ti₅Si₃C_x when using SiC fibers, as well as TiB and TiB₂ when using boron fibers. It is demonstrated that the use of fibers in the formation of titanium-matrix composite coatings enhances the impact strength of the resulting materials.

This paper considers the laser additive manufacturing process using the heat conduction equation with an instantaneous point heat source. It is shown that, under certain limitations, the depth of the substrate melt pool is accurately described by a self-similar solution. Two-parameter correlations for the melt pool depth and width with the Peclet number (the ratio of the scanning speed to the thermal diffusivity) and the dimensionless enthalpy (the ratio of the specific energy absorbed by the material to the energy required for melting) are derived. Criteria for the occurrence of two melting modes - keyhole and conduction - are established. It is demonstrated that the derived analytical correlations are in good agreement with experimental data.

This paper describes the CCDS2000 detonation coating system and demonstrates its capability for depositing electrically insulating and wear-resistant aluminum oxide coatings. The dielectric strength of the coatings exceeds 25 kV/mm within a thickness range of 50-300 μm. The coatings exhibit an electrical resistivity ρ_e > 2.67 × 10¹³ Ω·cm at 20°C and a relative humidity of up to 59%. A further increase in humidity caused a sharp decrease in ρ_e by 2-3 orders of magnitude. The coatings exhibit adhesion to a steel substrate of 60-70 MPa, a microhardness value HV0.1 = 1522-1655, and a porosity of 0.35-1.00%. Evidently, the C₂H₂ + 2O₂ detonation mixture is optimal for obtaining electrically insulating coatings, whereas the 0.69C₂H₂ + 0.53C₃H₆ + 2.51O₂ mixture yields the best wear resistance. The use of the dual-fuel mixture results in a fourfold increase in abrasive wear resistance and a 34% improvement in erosive wear resistance.

This study investigates a friction stir welding process for joining high-strength aluminum alloys. By implementing an active liquid cooling system and a post-weld aging treatment, a weld strength equivalent to the base material is achieved. The effect of cooling intensity on the microstructure and mechanical properties of the welds is examined. Optimal welding parameters for producing equal-strength joints are identified.

This study investigates the contact interaction between a thin composite strip and the rolls during rolling, focusing on conditions that ensure a horizontally straight exit end. The values of friction coefficients required to maintain a straight exit end during asymmetric rolling of a multilayer metallic material are determined. A finite element modeling of asymmetric rolling of a five-layer composite is performed with varying friction coefficients on rolls. The tool-workpiece interaction is modeled using the Amontons-Coulomb friction law, with the friction coefficient ranging from 0.1 to 0.4. The results show that a friction coefficient of 0.2 on both rolls minimizes the curvature of the exit end, resulting in an almost perfectly straight strip. For this optimal case, the stress-strain state is analyzed and the linear velocity distribution across the strip in the rolling direction is investigated. The analysis suggests that, upon passing across the deformation region, all material points move at a uniform velocity, which is significantly lower than the peripheral velocity of the lower roll, indicating persistent slip of the strip at the lower surface of the roll.

This paper addresses key challenges in the numerical simulation of gas-particle flows relevant to aerodynamics. Results are presented on the flow structure of the dispersed phase and the associated energy flux to a body surface. Particular emphasis is placed on simulating stochastic phenomena, including inter-particle collisions, the scattering of non-spherical particles upon wall rebound, and particle polydispersity, which are characteristic of real flows, but neglected in classical gas-particle flow theory. The collisional gas of particles within the carrier gas is simulated using a kinetic approach coupled with the direct simulation Monte Carlo (DSMC) method. A three-dimensional model for non-spherical particle-wall collision is implemented, and the particle size distribution in the free stream is described by a log-normal law. Using this approach, the dispersed phase flow structure was investigated for high-speed gas-particle flow over a blunt body (specifically, transverse flow around a cylinder). Energy loss distributions upon impact with the surface are calculated for particles of different shapes. The influence of the shielding effect during particle collisions on the energy loss is also examined.

This paper presents a method for predicting the movement of the laminar-turbulent transition front on the side surfaces of spherically blunted circular cones with account for surface roughness effects. The study demonstrates that mass ablation of the composite thermal protection systems on re-entry vehicles induces surface roughness along the flight trajectory. This roughness arises from differential ablation rates between the constituents of the material, such as fillers and binders, reinforcing frame elements, and the carbon matrix.

Non-equilibrium molecular dynamics (NEMD) simulations are performed to investigate the viscosity and rheology of benzene and nanofluids containing carbon nanotubes of two diameters and varying lengths. The results demonstrate that these fluids exhibit pseudoplastic (shear-thinning) behavior with increasing shear rate. Correlations are established for the critical shear rates as a function of nanotube concentration and length. At high shear rates, the viscosity differences between the nanofluids and the base fluid decrease monotonically, irrespective of nanotube length. This is attributed to shear-induced changes in the momentum dissipation mechanisms within the system.

This paper presents combined experimental and numerical results on the interaction of shock waves with highly porous, permeable barriers featuring both homogeneous and inhomogeneous spatial structures. The experiments are conducted in a shock tube for shock Mach numbers ranging within M = 1.2÷1.8. The experimental barriers comprise stacked wire meshes with triangular cells and layers of cellular nickel foam. The numerical simulations are based on the Reynolds-averaged Navier-Stokes (RANS) equations, utilizing a toroidal skeletal model for the porous media. The results demonstrate that minimal shock wave reflection is achieved using graded barriers, which consist of a sequence of mesh layers with progressively decreasing cell size, capped by a layer of fine-pore nickel foam.

This paper presents numerical simulation results for supersonic turbulent airflow in a planar channel with a backward-facing step, incorporating a volumetric heat source that simulates the heat release from chemical reactions. The simulations account for conjugate heat transfer between the flow and copper plates mounted into the channel walls, which act as heat flux sensor elements. The results show that the heat source reduces the flow velocity and causes an upstream shift of the supersonic wave structure. Increasing the source power enlarges the subsonic zone transversely, induced by flow separation at the shock impingement location. A localized subsonic region forms in the flow core, isolated from the near-wall subsonic zone by a narrow supersonic jet, confining the thermal plume to the core flow. A sharp flow restructuring is triggered when the local separation zone merges with the recirculation zone downstream of the backward-facing step, allowing for the gas (warmed up by the heat source) to penetrate the enlarged separation bubble. This narrows the effective flow region, causing a compression wave, rather than an expansion wave, to form at the step edge. Consequently, the core flow temperature decreases while wall heat fluxes increase substantially.

The gas separation process via a membrane-sorption method шs investigated using a hydrogen-helium mixture and silica microspheres. Experimental and numerical modeling of a two-stage membrane-sorption process for hydrogen-helium mixture separation is carried out. The experimental two-stage separation at 22°C demonstrates an increase in the helium volume fraction from 10.5% in the feed to 57.8% after the first stage and 93.3% after the second stage. Evidently, the final helium volume fraction in the enriched stream is primarily influenced by the amount of depleted mixture remaining in the adsorber prior to the desorption cycle.

Quantitative thermography is used to study the effect of streamwise-orientated, quasi-two-dimensional roughness elements (strips) on the laminar-turbulent transition location on a 45° swept wing model under various test conditions. The efficacy of these sliding roughness elements for flow laminarization is investigated under elevated freestream turbulence levels and increased surface roughness. The results demonstrate that this laminarization method is also robust to moderate variations in the freestream velocity.