Home – Home – Jornals – Thermophysics and Aeromechanics 2026 number 2

This article addresses the problem of line identification in high-resolution vibrational-rotational spectra. We suggest an approach based on heuristic search applied in artificial intelligence systems for automatically identifying a set of molecular energy levels observed in a spectrum. Such systems solve the problem of finding a sequence of operations for transforming input data (formulas, knowledge) that brings the data to a certain target or desired state. The proposed approach simultaneously analyzes several rotational sublevels in a spectrum, thus enabling more reliable identification of the corresponding spectral lines using more information. The results can be used in optical atmospheric measurements and molecular physics.

Modern databases such as HITRAN and GEISA provide spectral line parameters only for Voigt profile (VP) calculations. Spectral modeling for describing various processes in many areas of chemistry, physics, earth sciences, and engineering uses this line profile for collisional isolated transitions. However, the use of VP leads to high errors as compared to high-precision experimental spectra. More sophisticated models have been developed for spectral modeling that take into account “non-Voigt" effects, such as changes in molecular velocity due to collisions and the velocity dependence of the broadening and shift coefficients during collisions. In this paper, we present the results of high-precision measurements and analysis of the absorption spectra in ¹²C¹⁶O in the pressure range from 0.001 to 0.3 atm using “non-Voigt” profiles. We analyze the pressure dependences of parameters of VP, RP, qSDVP-Δ₂, qSDVP, and qSDRP profiles of the P3-P8 lines of ¹²C¹⁶O. We show that the intensity S and the profile parameters Γ₀ and Δ₀ linearly depend on pressure, regardless of the profile type. The intensities S and the broadening Г₀/ P _CO and shift Δ₀/ P _CO coefficients for the profiles qSDVP-Δ₂ and qSDVP coincide with the experimental accuracy. Calculations using the VP demonstrate deviations of S , Г₀/ P _CO, and Δ₀/ P _CO values from the results for qSDVP-Δ₂ and qSDVP within 1-2%. A nonlinear dependence of Г₂ and Δ₂ on pressure is observed when using qSDVP-Δ₂, qSDVP, and qSDRP. The applicability limits of the profile models for describing high-precision experimental spectra of ¹²C¹⁶O molecule are estimated.

Optical radiation propagating in the atmosphere is partially absorbed by air, thus heating it; at the same time, an optical radiation beam acts as a linear extended heat source. The resulting convective phenomena contribute to atmospheric turbulence. Indoors, this convective turbulence has features related to spatial limitations and the presence of other heat sources. In this paper, convective air motions in a vicinity of a group of linear extended optical sources in a horizontal configuration of an open-side room under external wind influence are studied by numerically solving three-dimensional Navier-Stokes equations. To parallelize the calculations, a computing cluster with MPI interface was used. Convective cells arising along inclined optical beams and the corresponding velocity and temperature fields are described. It was found that the shape and location of the cells are determined by the inclination of beams optical axis and the configuration of the room. The evolution of temperature and velocity fields is shown. Spatial spectra of temperature fluctuations in various directions, including in the vicinity of optical paths, are constructed. The causes are described and the mutual effects of the beams are estimated upon changes in the structural characteristic of air refractive index fluctuations in the vicinity of inclined optical paths. The influence of the external wind on the thermal traces of optical radiation beams inside and outside the room is considered. Upon completion of the numerical experiment, there is a turbulence inside the room with spectrum of temperature fluctuations similar to Kolmogorov spectrum. The considered situations can be observed in specialized rooms of optical systems when air is heated by optical radiation of varying intensity. The resulting turbulence fields of convective and dynamic nature significantly impact the operation of recording devices. The results are important for predicting the correct operation of such devices and for evaluating the mutual influence of optical beams.

A specific feature of surface layer electricity research is the requirement for synchronized measurements and subsequent data interpretation to accurately distinguish and evaluate the impact of local disturbances and global electric field variations on observed electrical characteristics. To address the challenge of interpreting atmospheric electricity measurements, a mathematical model is required to establish a definitive link between global and local disturbances and the measured values. This paper presents a potential implementation of such a model in the form of a total current equation describing the daily dynamics of the electric field intensity in the surface air layer. The spatiotemporal structure of the turbulent surface air layer, which is formed under the influence of a global unitary variation in the ionospheric potential and a local turbulent generator with independent daily dynamics, has been studied. The work generalizes studies of daily variations in the electric field strength of the surface layer for the cases of constant total current at the upper boundary of the surface layer. The profiles of electric field strength, conduction current density, and turbulent current density at different times during the day were calculated. Their dependence on the degree of turbulent mixing in the surface air layer has been established. The calculation results can be useful in analyzing data from ground-based atmospheric-electric observations.

Spatial irradiance is a defining characteristic of radiation during the thermal impact of a laser beam on biological tissues, powders, and other scattering media. The provides a theoretical consideration of multiple light scattering in the volume of a semi-infinite diffuse scattering medium (DSM). Calculations are made for pressed dielectric powders with refractive indices n = 1.47, 1.72, and 2.00 at a wavelength of 1.06 μm (the first harmonic of a neodymium laser). The diffuse reflectance coefficients ρ(1 - Λ) calculated by the Monte Carlo method and in the Kubelka-Munk approximation are compared. A linear relationship is established between the spatial irradiance in DSM volume and the diffuse reflectance coefficient. The precisions and applicability limits of the original and corrected Kubelka-Munk formulas are determined. A complex relationship is ascertained between the single scattering albedo Λ and the angular dependence of a photon flux incident on the DSM-air interface f (α). In particular, it was shown that for Λ → 1 and isotropy scattering, f (α) = cos(α), where a is the photon incidence angle. The results can be used for the development of methods for determining spatial irradiance and, for example, in laser medicine.

Laser-induced plasma diagnostics in aerosols is complicated by plasma inhomogeneity. In this work, the electron density of laser-induced plasma was evaluated based on Ba II 455.4, Na I 589, Al I 396.2, Ca II 393.4 and Fe I 542.4 nm emission lines for the case of using equipment on mobile carriers. It was found that the electron density is minimal for the Ba II line and maximal for the Na I line; the difference in the values attained almost an order of magnitude, which was attributed to differences in the diffusion lengths of the elements. It was experimentally shown that the plasma electron temperature weakly depends on time in the 2-4 ms range at exposure times of 40 and 150 ms. It was confirmed that recombination pumping of the upper levels of transitions under study did not significantly affect the intensity of the analytical lines. Based on the analysis of the rate constants of excitation from the ground state, the limit of detection was found to be the worst for Al I 396.2 nm line. The results of the work can be used in emission spectral analysis of aerosols.

The onset of polar stratospheric cloud (PSC) formation and chlorine activation is so far considered to be the temperature threshold of formation of nitric acid trihydrate T _NAT, below which the HNO₃ concentration sharply increases in PSC particles. In this paper, we use the data on the minimal temperature, maximal negative deviations of ozone concentration from multiyear average, and maximal nitric acid (HNO₃) concentration in the Arctic stratosphere at four sites: Eureka, Canada (EUR); Ny-Ålesund, Norway (NAD); Thule, Greenland (THU); and Resolute, Canada (RES) for calculations of the maximal HNO₃ concentrations and the total HNO₃ columns. The maximal HNO₃ concentrations decrease throughout the winter until late February at all observation sites considered here due to condensation of gas-phase HNO₃ on PSC particles. The concentrations start to grow after return of sunlight to polar latitudes due to PSC sublimation and HNO₃ export from peripheral areas of the vortex during its deformation. The HNO₃ content in the winter-spring stratosphere of the Arctic is an important indicator of the PSC formation and breakup.

The analysis of statistical properties of aerosol density fluctuations can serve a starting point for the study of the random component of wind velocity field. In this paper, we analyze the fluctuations of power of a scattered signal measured by an airborne lidar in the DELICAT (DEmonstration of LIdar based Clear Air Turbulence detection) project experiment. A new method for the study of aerosol clouds based on 2D Fourier transform was proposed. Flight segments with constant altitude, direction, and velocity of aircraft were selected for the analysis. A signal was considered in the coordinate system with the abscissa axis representing the distance from the aircraft to a scattering volume and the ordinate axis representing the aircraft path relative to air mass. In these coordinates, aerosol clouds appear as stripes inclined at an angle of 45°. Spatial spectra of aerosol density fluctuations are obtained. For areas where aerosol is observed, 2D spectra have a peak in the vicinity of the main diagonal of the frequency plane. Their diagonal sections are equal to estimates of 1D spatial spectra of aerosol concentration fluctuations within the following approximations: 1) clouds are stationary on a time scale on the order of 1 min, 2) variations in the direction of the sounding line are negligibly small. The slope of 1D spectra has been estimated.

The study of the propagation of high-power ultrashort pulses in the atmosphere is an urgent problem in optics and laser physics. In this paper, we consider the conditions for modifying the basic sensing equation using supercontinuum radiation concentrated in postfilament channels associated with nonlinear foci and filamentation zones of a high-power femtosecond laser pulse. A method for determining the attenuation coefficient is proposed, similar to the well-known logarithmic derivative method used in single-frequency laser sensing. As an example, for a layered homogeneous non-absorbing medium in the single-scattering approximation, the attenuation coefficient is found using radiation at the wavelengths of the supercontinuum concentrated in postfilament channels formed in two spatially spaced nonlinear foci. It is concluded that the modified sensing equation for spatially spaced nonlinear foci is promising for evaluating the effectiveness of broadband optoelectronic communication systems, location detection, and rangefinding.

The problem of air pollution in Crimea is of interest due to its geographical characteristics and resort use. Experimental studies on the composition and temporal variability of aerosols in the surface air layer were conducted in the southeastern part of the Crimean Peninsula at the background environmental monitoring station of T.I. Vyazemsky Karadag Scientific Station - a nature reserve of the Russian Academy of Sciences, a branch of the Federal Research Center of the Southern Oceanological Institute, from March 21 to June 17, 2020. For the first time, data are presented on temporal variations in the daily average mass concentration of aerosol, chemical elements in its composition, and aerosol particles of 0.15-1.5 mm and 0.2-5.0 mm in size. Concentrations of 25 selected chemical elements were determined. The comparison was made between the elemental composition of the aerosol and its size distribution, meteorological conditions, and the direction of long-range transport of air masses. The size of particles transporting heavy metals and metalloids (Zn, Mo, Cd, Pb, Bi, Se, Sn, and Sb), as well as elements of global origin was determined. The elements S, Cu, and Hg, for which no significant correlation with particle size was found, are likely of mixed origin due to competition between natural and anthropogenic sources in different periods. The results characterize the aerosol parameters during the spring-summer period in the eastern part of Crimea and are of interest to specialists involved in environmental monitoring in the resort and recreational region.

To better understand the current trends in the growth of greenhouse gas concentrations on a regional scale, it is necessary to analyze their isotopic composition in order to identify their sources and sinks, which determine both seasonal and long-term changes in their atmospheric content. Continuous observations of atmospheric CO₂ and CH₄ and the carbon isotope composition of their molecules carried out in 2022-2024 at the Fonovaya observatory enabled the range of background values and seasonal pattern of δ¹³C-CO₂ and δ¹³C-CH₄ in the atmosphere of the southern taiga zone of Western Siberia to be determined. The average daytime (01-05 pm) values of δ¹³C-CO₂ and δ¹³C-CH₄ varied in the ranges -9.2 to -5.7‰ and -51.7 to -46.5‰, respectively. The analysis of background values revealed a sharp summer minimum in CO₂ concentration and, conversely, a maximum in δ¹³C-CO₂, indicating intensive uptake of ¹²CO₂ by the regional terrestrial ecosystems. Winter values of both CO₂ concentration and δ¹³C-CO₂ are consistent with data from other greenhouse gas monitoring stations in the Northern Hemisphere. The pattern of seasonal variations in atmospheric CH₄ mixing ratios and δ¹³C-CH₄ values in the region under study indicates that the winter maximum in CH₄ content is driven by anthropogenic factors, while the summer maximum, by the predominance of biogenic methane emissions from Western Siberian wetlands. Using the Keeling plot method, source/sink signatures influencing changes in atmospheric CO₂ and CH₄ concentrations in the area under study were determined for each month of the year. The results can be used when analyzing and interpreting long-term observations of greenhouse gases in Siberia.

Various failure modes of the electrodes and insulators of pulsed X-ray tubes with explosive electron emission operating in a single-pulse flash mode are investigated. The operating parameters are as follows: capacitor bank discharge energy into the tube 30-50 J, pulse duration 40-100 ns, and electron energy incident on the anode 200-300 keV. The following experimentally observed damage types are identified: sublimation, spallation, surface melting, formation of Taylor cones drawn from the surface, droplet ejection, surface etching in the form of deep longitudinal grooves, periodic chevron-like surface patterns, deep surface cracks, micrometer-scale droplets atop Taylor cones that have traveled from the cathode to the anode, cathode bombardment by material ejected from the anode, dust-like deposition in the form of island films on the cathode and insulator, and surface flashover along the insulator accompanied by film evaporation. The mechanisms underlying the effects of high-current pulsed electron beams on the components and the influence of these damage types on the service life of the tubes are discussed.

A comprehensive experimental study aimed at generating a training dataset for the development of a neural network model to optimize the control of environmental and energy performance parameters of hydrocarbon fuel flame combustion is presented. Flame characteristics are investigated for liquid fuel combustion using a flare burner with a thermal capacity of 300-1500 kW and mechanical atomization. The experiments examine operating modes at various power levels (400, 700, and 1000 kW) and equivalence ratios (1.06, 1.17, 1.28, and 1.40). Simultaneous measurements of flame temperature, combustion product gas composition analysis, and visual flame monitoring are performed. The dependence of combustion parameters on operating conditions is established: an increase in power and a decrease in the equivalence ratio elevate the flame temperature. Alternatively, dropping airflow reduces CO concentration to <10 mg/m³ but increases NO_x emissions to >125 mg/m³. Correlations between the visual flame characteristics (size and luminous intensity) and the equipment operating parameters are identified, which opens prospects for the development of automated machine-vision-based control systems.

An asymptotic model of large-amplitude stationary inertial waves in an axisymmetric swirling flow of an ideal fluid in a circular pipe of varying diameter is developed. Calculations are performed for a flow with solid-body rotation far upstream; in this case, vortex breakdown is caused by the pipe geometry and the emergence of a separation zone. The separation zone is shown to be axially asymmetric. For a separation region to form at a fixed position relative to the onset of pipe expansion, the flow swirl should be stronger for larger pipe expansion angles.

Results of an experimental study on the effectiveness of controlling incompressible turbulent flow over an asymmetric Clark Z airfoil using a perforated surface are presented. The perforated surface consists of an array of cylindrical cavities or through-holes with variable geometric parameters. The cavities are located on the lower surface of the wing, most of which is exposed to zero-pressure-gradient flow. The study is conducted over a chord Reynolds number range of Re_c = (0.601-1.324) × 10⁶ at an angle of attack of 3.6°, corresponding to a momentum thickness Reynolds number range at the perforated surface inlet Re_θ = 527-992. Particular attention is given to a previously unexplored analysis of the potential for reducing the aerodynamic drag of the airfoil under these conditions. It is shown that none of the perforated surface configurations under study provides a drag reduction within the experimental uncertainty.

The development of a single thermal disturbance in a laminar boundary layer at a Mach number M = 1.43 in the presence of a pressure gradient induced by a shock wave emanating from a wedge with an angle of 2° is investigated using direct numerical simulation. Calculations are performed using the HyCFS-R code developed at the ITAM SB RAS. The evolution of the disturbance is examined in a zero-pressure-gradient boundary layer, during passage through the interaction region, and in the wake. A single thermal disturbance is shown to generate a localized wave packet. Spectral analysis is used to determine the packet composition and its evolution through the interaction zone. The influence of the pressure gradient on disturbance amplification is assessed, and the disturbance development in the boundary-layer-shock-wave interaction region up to the onset of laminar-turbulent transition is analyzed. A comparative analysis is performed for two types of boundary conditions applied at the lateral boundaries of the computational domain. The results show that the combined effect of the thermal disturbance and the shock wave plays a dominant role in boundary-layer destabilization, which should be taken into account in transition control strategies for supersonic flows.

The flow structure and pressure fluctuation characteristics generated when a supersonic underexpanded jet impinges on a flat semi-infinite obstacle with a coaxial hole are investigated. Different interaction regimes are found to arise depending on the hole diameter and the distance from the nozzle exit to the obstacle. The presence of a hole in the obstacle is found to significantly intensify wall pressure fluctuations for nozzle-to-obstacle distances in the following range: h/D_a = 1-4. In the case where h/D_a = 4-15, the interaction regimes are similar to those observed for a jet impinging on a solid (impermeable) obstacle.

This paper presents the results of a study of the parachute -type fragmentation process. This process serves as a source of the dispersed phase in various natural and industrial multiphase flows in which a planar liquid surface is exposed to a gas stream. Experiments are performed using shadowgraph visualization and high-speed imaging, with artificial initiation of the process under controlled conditions. Computer-based image processing is used to determine the dome dimensions and film thickness, as well as to detect the resulting droplets and quantify their number. Based on the analysis of the results, it is concluded that rupture of the dome film occurs due to Rayleigh-Taylor instability. The dependence of the average number of droplets produced by rupture of the parachute dome film on the governing parameter-the Weber number-is obtained.

The effect of free rotation of the cylindrical housing of a centrifugal reactor on the structure of vortex fluid flow is investigated experimentally. The working fluid is driven by rotation of the upper disk, while the reactor housing is free to rotate about its axis under the action of viscous friction from the fluid. The flow energy expended in overcoming friction in the stationary housing is converted into kinetic energy of rotation of the reactor housing. Even slight free rotation of the reactor housing is found to lead to a significant intensification of the vortex motion. The proposed reactor design enables efficient control of vortex flows without the additional energy expenditure required for forced rotation of the sidewalls at a fixed speed. The results obtained can be used in the development of compact centrifugal reactors for biological, chemical, and energy technologies.

Forced nonlinear oscillations of a gas bubble in a viscoelastic fluid are considered for the case where the oscillation frequency of the external fluid pressure coincides with the undamped linear resonant frequency of the bubble. The averaging method is applied to derive a formula for the dependence of the bubble oscillation amplitude on the external pressure amplitude, the adiabatic exponent, and the viscoelastic properties of the fluid. Computational results obtained using this formula are shown to be in good agreement with numerical simulation results.

The variable N-factor method, which is one of the most effective modern approaches for predicting the laminar-turbulent transition location in boundary layers, is improved. The determination of the threshold N-factor for swept wings is refined by taking into account the range of transverse roughness scales on the wing leading edge that are dangerous from the standpoint of cross-flow instability and boundary-layer receptivity. The proposed modification does not require additional numerical analysis, as it is based on standard linear stability theory calculations and empirical data on the efficiency of boundary-layer receptivity to roughness in the generation of cross-flow instability vortices. The resulting dependences of the critical N-factor on the dimensionless leading-edge roughness are presented and calibrated against our own experimental data.

The interaction of a plane oblique shock wave with a vortex system arising from flow separation at the edge of a dihedral model with an opening angle of 270° is examined. The shock generator, which is a thin plate, and the model are positioned at the same angle of attack of 16°. A downstream-expanding separation vortex is generated by the pressure difference between the upper and side faces of the model, while the shock wave incident from the generator causes extensive boundary-layer separation on the surface of the side face. The complex interaction between the shock-induced separated flow and the stalled flow leads to the formation of a cylindrical vortex detached from the surface.

The effect of preloading on the porosity change of water-saturated clay soils is investigated. A numerical model of one-dimensional filtration in a porous medium with variable permeability dependent on the applied load is employed for the analysis. The boundary conditions are specified in terms of filtration velocities, and the load effect is modeled through changes in the permeability coefficient. The results obtained are shown to be in good agreement with experimental data. The proposed description of porosity evolution enables more accurate prediction of soil behavior during fluid filtration.

A numerical study of the problem of symmetric capillary filling with a viscous incompressible fluid in the nonisothermal case is performed. The flow is described using the Pavlovskii model. In this problem, the dynamic contact angle issue arises when the impingement angle differs from 0 or π. This issue originates from the incompatibility between the free-surface boundary conditions and the no-slip condition on the solid wall in the vicinity of the moving three-phase contact line. To close the formulation, the no-slip condition is replaced by a generalized Navier slip condition. The influence of the dynamic contact angle on the temperature near the three-phase contact line is investigated for flows with low capillary numbers.

A method for controlling the heat flux density during boiling of water in the context of modeling a two-phase cooling system for power electronics is examined. The challenge of increasing thermal loads and amplifying power devices lies in the inability to remove such high heat fluxes from the power module. The most efficient heat removal mechanism, boiling, is limited by the onset of a boiling crisis. A simplified method for enhancing vapor removal from the heat transfer surface using adiabatic inserts is proposed. The inserts break up vapor bubbles into smaller ones, reducing the likelihood of vapor film formation on the surface. Additionally, they promote liquid sliding along the unheated isothermal insert wall, unimpeded by vapor bubbles. The primary experimental technique is gradient heatmetry. The dependence of the local heat flux density on the simulated power module temperature is obtained for various fin pitches with adiabatic inserts. The effectiveness of the proposed heat flux density control method is demonstrated.

Results of a numerical analysis of the transition from steady to oscillatory laminar flow in gravitational convection of an incompressible fluid in a closed cavity heated from the side are presented for various Grashof and Prandtl numbers. The influence of the nonlinear dependence of convective flow on the Prandtl number on the flow structure and its temperature and concentration stratification is demonstrated.

The influence of tube walls on laser-induced subcooled boiling at the end of a thin laser fiber placed in a tube is investigated numerically. It is shown that, in the case of tubes with a radius fourfold greater than the bubble radius at maximum expansion, the velocity of the cumulative jet formed upon collapse of the vapor bubble is equal to that in an unbounded space. As the tube radius decreases, the jet velocity decreases due to rebound , which is bubble re-expansion that prevents jet formation. A further reduction in radius leads to a predominance of axial fluid flow within the tube and subsequent jet destruction. The influence of tube radius and length, as well as fiber length, on the bubble shape and volumetric flow rates through the tube end sections is demonstrated. Dimensionless parameters at which the volumetric flow rate through these sections reaches its maximum are identified, which is particularly important for medical applications.

Heterogeneous boron carbide-based ceramics with vanadium diboride additions, produced by uniaxial hot pressing, are investigated. During sintering, vanadium diboride was synthesized by carboborothermic reduction from vanadium oxide, as confirmed by X-ray diffraction analysis. The microstructure of the B₄C-VB₂ heterogeneous ceramics consists of uniformly distributed vanadium diboride grains in a boron carbide matrix. Increasing the vanadium diboride molar fraction from 0 to 5% is found to increase the fracture toughness of the ceramics from 2.0 to 5.5 MPa·m^1/2.

This paper describes the Love wave propagation in a layer overlying a half-space consisting of relatively thin layers, with slip at the contact boundaries. The slip contact conditions in the finely layered medium are specified by a linear Winkler-type condition for shear stresses. This medium is described by an asymptotically exact homogenized model that includes second-order terms in a small parameter-the layer thickness. Dispersion relations for Love waves are derived. Typical dispersion curves and through-thickness wave profiles are constructed. A parametric analysis is performed, revealing differences from the case of a homogeneous half-space.

The characteristics of the elastoplastic transition and subsequent hardening in the strain curve segment up to 4% deformation are investigated in homogeneous AMg5 alloy specimens and in specimens containing a friction stir weld. Depending on the strain rate, the elastoplastic transition is found to occur through the formation and propagation of localized plasticity autowaves of switching or excitation types. These autowaves form at stress concentrators, such as weld seam boundaries.

A specialized experimental facility developed by the authors is described. The facility enables in vitro blood flow studies in vascular sections of various configurations while maintaining similarity to real hemodynamic conditions. Results of its performance evaluation are presented. The facility is shown to have several advantages over existing analogs. It enables flow visualization and measurements of flow parameters under both steady and pulsating conditions. The facility produces a waveform that matches the actual blood flow variation over a cardiac cycle, including a high-amplitude antegrade flow peak and a retrograde flow (flow rate reversal) segment. It also demonstrates stability and high reproducibility of the specified operating conditions. Experimental results obtained with this facility can be used to validate existing and future numerical models of vascular hemodynamics.

The process of blood pumping through an artificial vessel using a vibro-volumetric perfusion pump is investigated. The device is essentially an expanding channel with vibrating walls, approximating a diffuser in its simplest form. The relationship between the vibration parameters and the geometric characteristics of the device and the flow rate of transported blood is examined. A mathematical perfusion model is presented. This model incorporates a three-component rheological model of blood and a two-mass model of the oscillatory system of the device. The interaction between the vibrating walls, the deformable vessel, and the blood are also accounted for in the model presented.

An experimental and numerical study was conducted to examine the effect of a passive perturbation from a vortex generator on heat transfer in a bubbly flow in a flat channel. Wall temperature measurements were taken using an infrared camera. To describe the flow dynamics and heat and mass transfer in the gas and dispersed phases, unsteady Reynolds-averaged Navier-Stokes equations were used, written taking into account the presence of polydisperse bubbles within the Eulerian approach. The influence of flow velocity, air bubble concentration, and vortex generator height on heat transfer in a two-phase gas-liquid flow was studied. It was found that the thermal pattern of separated two-phase bubbly flow behind an obstacle in the presence of a passive disturbance differs significantly from the dynamic pattern. The results demonstrated an increase in heat transfer in the bubbly flow behind the obstacle. A comparison was made between the obtained experimental and numerical data on heat transfer in a two-phase turbulent bubbly flow in the presence of an obstacle installed on the channel wall, and satisfactory agreement was demonstrated in terms of the characteristics of convective heat transfer.

This paper aims to expand the capabilities of experimental studies of the gas dynamics of supersonic, highly rarefied jets by employing new diagnostic tools for determining flow energy parameters. Known methods for measuring temperature in a rarefied gas flow are considered. A detailed description of the chosen methodology and equipment for measuring transverse molecular beam density (or intensity) profiles and determining the perpendicular velocity ratio from them is provided. A comparison of a large array of experimental data with known theoretical models confirms the reliability of the obtained information. The possibilities and conditions for calculating the translational (perpendicular) temperature are considered. The error and range of reliability of the obtained results, the influence of concomitant processes of skimmer interaction and penetration of background gas into the jet on the recorded parameters, as well as the possibility of expanding the range of research using this method are discussed.

A numerical model for multiphase immiscible flows in porous media is presented. It is based on the lattice Boltzmann (LBM) method using a color gradient. An algorithm for specifying arbitrary wetting angles at interfaces with a solid surface is implemented. The model is verified using Laplace's law and liquid lens geometry for two- and three-phase systems. Numerical modeling, applied to oil displacement experiments in a digital core model obtained from micro-computed tomography data, allowed us to obtain a physically correct saturation distribution, including the effects of capillary locking and breakthrough channels. The developed approach can be used to analyze and optimize oil production processes, study residual saturation and storage of carbon dioxide in geological reservoirs.

The segregation in melts of the Li-K-Pb system in the temperature range of 941-1187 K has been studied using the gamma-ray attenuation technique. It has been shown that the addition of 28.6 at.% Pb to the liquid Li-K system is insufficient to exit the immiscibility region, the boundaries of which remain unknown. The gamma-ray linear attenuation coefficient profiles in liquid alloys Li₄KPb₂ and Li₁₆K₃Pb₇ have been studied at two temperatures. It has been shown that during the cooling process homogeneous melts of Li₄KPb₂ and Li₁₆K₃Pb₇ reach the immiscibility region at temperatures of about 1045 and 1063 K, respectively.

The article presents the results of an experimental study of the efficiency of controlling a supersonic turbulent boundary layer on a flat surface using distributed positive air mass transfer through a finely perforated wall. The experiments were performed at a Mach number of 2 and a unit Reynolds number of 12.5 x 106 m^-1. The mass transfer rate varied from 0 to 0.00941. A significant effect of mass transfer on the skin friction coefficient is demonstrated, with the reduction at the end of the active control region reaching more than 80% compared to the baseline value. It was found that with spontaneous mass transfer, achieved through the natural difference between barometric and static pressure in the working section of the wind tunnel, it is also possible to achieve a significant reduction in the skin friction coefficient, down to zero at the end of the control region.

The results of an experimental study of the thermal conductivity (λ), thermal diffusivity ( a ), heat capacity (Cp), density (ρ), and elastic moduli of four polymer composite samples as functions of temperature and pressure are presented. The polymers were synthesized by supercritical dispersion using a CO₂ solution (SEDS). Thermal conductivity measurements were carried out in the temperature range from 293 K to 343 K at a pressure of 0.101 MPa; sample PP2 was studied at a pressure of up to 40 MPa using the stationary flat layer method. The thermal diffusivity coefficient was measured in the temperature range from 293 K to 368 K at atmospheric pressure using a Netzsch LFA 457 (Laser Flash, LFA) device using a non-contact method. The heat capacity of the same samples was measured in the temperature range from 129 K to 363 K using a DSC 204 F1 differential scanning calorimeter. The elastic moduli were obtained by measuring the propagation velocity of longitudinal and transverse ultrasonic waves using the pulsed method.

The data on the concentrations of phenolic compounds, photosynthetic pigments, pectin substances and triterpenoid saponins in the leaves of Chlorophytum сomosum Thunb. Jacques are presented, the antioxidant and antiviral activity of the extracts of this plant species is assessed. High concentrations of chlorophyll a and b (434.67 and 245.11 mg/100 g, respectively), tannins (82.34 mg/g), catechins (0.73 mg/g), hydroxycinnamic acids (36.67 mg/g), saponins (64.53 mg/g), carotenoids (75.70 mg/100 g) and pectin substances are detected in the leaves of this plant species. The total content of phenolic compounds and flavonols was termed as insignificant. The water-ethanol extracts of the leaves exhibited antiradical activity in the reaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl. The antiviral activity of the aqueous extract was detected with respect to the avian virus A/chicken/ Kurgan/05/2005 (H5N1).

A new synthetic approach has been developed on the structure modification of bioactive furanolabdanoid phlomisoic acid methyl ester by introducing 1,3,4-oxadiazolylcarbonyl fragment at position 16 of the carbon framework. The key steps of the synthesis are the preparation of (2-(2-(aryloyl/hetaryloyl)hydrazinyl)-2-oxoacetyl)furans and their subsequent heterocyclisation proceeding under the action of dehydrating agents. The cytotoxic properties of the obtained compounds were evaluated with MTT test against three human cancer cell lines. It has been shown that introduction of (5-(pyridin-4-yl)-1,3,4-oxadiazol-1-yl)methanone motif on the furan ring of the starting labdanoid significantly increases the cytotoxic action.