Home – Home – Jornals – Thermophysics and Aeromechanics 2025 number 5

Using LA ICP MS dating of zircons, the age of the tuff (633±7 million years) of the Bolshoi Patom Formation at the base of the Vendian reference section in the south of the Siberian Platform (Ura Uplift) was estimated. The Vendian of the Siberian Platform was found to include the last Cryogenian (Marinoan) glaciation, and the postglacial sequence of the Vendian corresponds to the Ediacaran. In light of the obtained dating, the chronostratigraphy of the Riphean-Vendian deposits on the Ura Uplift and in adjacent areas is considered. The available geochronological and sequence stratigraphic data indicate the presence of hidden stratigraphic unconformity above the glacial horizon at the base of the Vendian, caused by glacio-isostasy.

This paper presents the results of developing a pulse analyzer for a borehole geophysical instrument intended for spectrometric gamma-ray logging. The module is implemented using a field-programmable gate array and enables real-time signal processing. An algorithm for converting biexponential responses of a scintillation detector into trapezoidal pulses is proposed. The efficiency of the implemented algorithm has been demonstrated in resolving pile-up pulses with a time delay of 300 ns. Using calibrated gamma-ray sources — Am‑241, Eu‑152, Cs‑137, Co‑60, and Th‑228 — the system's energy coverage in the range of 50 to 3000 keV is confirmed. The pulse analyzer features universal architecture and is compatible with various types of gamma-ray detectors.

The article presents the results of geochronological, geochemical and isotopic studies of intrusive complexes in the central and southern parts of Rudny Altai, which until recently have been practically uncharacterized using modern research methods. The results of U-Pb dating of zircon grains from igneous rocks (26 determinations) made it possible to establish 4 stages of endogenous activity: 1) Late Devonian (~ 370–360 Ma); 2) the end of the Early Carboniferous (~ 330–320 Ma); 3) Middle–Late Carboniferous (~ 315–305 Ma); 4) Early Permian (300–286 Ma). During each stage, both mafic and granitoid magmatism was manifested, which indicates the active development of mantle-crust interaction processes. An examination of the geochemical characteristics of the studied rocks allowed us to draw conclusions about the sources of magmas and the conditions of their melting, while comparison with geological and geochronological data from neighboring regions allowed us to determine the most likely geodynamic regimes for the manifestation of intrusive magmatism in the region. In the Late Devonian, magmatism occurred in a subduction setting on the active margin of the Siberian continent. At the end of the Early Carboniferous, magmatism was associated with the onset of orogenic processes during the formation of the Zaisan folded system orogenic structure. In the Middle to Late Carboniferous, magmatic activity reflects the onset of post-orogenic extension. Early Permian magmatism is due to a combination of post-orogenic extension and the activity of the Tarim large igneous province, formed as a result of the impact of the mantle plume of the same name on the lithosphere. Special attention is given to metallogenic aspects, and suggestions are made regarding the absence of ore deposits associated with intrusive magmatism in the region..

An automatic method is proposed for counting maize seedlings under conditions of substantial weed infestation and partial occlusion using ultra-high-resolution (<0.5 cm/pixel) RGB imagery acquired from an unmanned aerial vehicle. The method is based on a combination of computer vision and machine learning algorithms. Experimental results demonstrate that the accuracy of estimating the number of maize seedlings at early growth stages averaged 97%.

A histogram scene-based algorithm is developed to compensate for gain and bias non-uniformity in infrared focal-plane arrays. The statistical scene-based calibration method is proposed. Experimental results illustrating the effectiveness of the method are presented.

Issues related to the variational approach to the problem of non-parametric a priori uncertainty are disclosed is a method of converting a system of a priori stochastic differential equations, which enables to reduce the initial problem of nonlinear filtering of a multidimensional Markov process to a problem of filtering a new Markov process, characterised by a zero drift vector. The main provisions of the method of independent first integrals are given, allowing to provide the required transformation of linear systems of a priori stochastic differential equations. Filtering algorithms were constructed, in which the method of transforming multidimensional densities is used to restore the initial a priori and a posteriori densities of the probability distribution. An example of filtering the phase of a narrowband random process using the proposed conversion method is given. It has been shown that the proposed method of transformation using numerical integration reduces the requirements for the selection of parameters of the posterior density of the probability distribution of the vector of filtered parameters

The article discusses algorithms and neural network models for semantic segmentation of the Amur River water surface areas obtained using aerial photography. A dataset has been prepared for training a neural network based on aerial photography materials of the Amur River water area. The article presents the results of research on the accuracy of prediction of the most popular models in the field of semantic segmentation, such as UNet++, DeepLabV++, FPNet, and SAM. The experiments used the IoU (Jaccard similarity measure) and Boundure IoU (object boundary segmentation accuracy assessment) metrics. Computational experiments were conducted to measure the accuracy of the trained models in order to select the optimal parameters. As a result, it was found that the UNet++ model has an advantage in terms of segmentation accuracy, with an average Boundure IoU score of > 0.9. The developed algorithms and trained neural network models can be used in river water surface monitoring systems based on orthophoto images to determine the boundaries of the coastal zone.

The superior efficiency of the piecewise linear approximation method based on Delaunay triangulation has been demonstrated. This method completely eliminates negative concentration values on the resulting surface and exhibits the most favorable gradient distribution, with only 3.33% of gradients exceeding 75 ppm across the entire point cloud surface. The significance of the obtained results lies in the confirmed ability of this approximation method to generate highly reliable and physically accurate regime maps. These maps are essential for predicting critical emission levels, such as carbon monoxide (CO) and nitrogen oxides (NOx), during liquid hydrocarbon fuel combustion, enabling the development of effective burner optimization strategies to minimize environmental impact and maximize combustion efficiency in practical power installations.

Modern trends in underwater robotics development are focused on creating fully autonomous unmanned underwater vehicles (UUVs) equipped with multi-link manipulators (MLMs) and capable of performing complex research, manipulation, and technological operations in dynamic and uncertain underwater environments without direct operator involvement. The key challenge in UUV implementation is the generation and adaptive real-time adjustment of control programs based on data about the current environmental conditions obtained from the UUV's onboard sensors and MLM sensors. This paper presents a comprehensive set of tools for an intelligent UUV mission planner, including its information and software components, as well as development methodology. The proposed planner provides decomposition of strategic tasks into elementary operations with dynamic selection of their execution sequence and parameters depending on actual data and external conditions. The architecture of the developed software is based on principles of modularity and scalability, allowing the system to be adapted for various classes of UUVs and mission types. The presented solution contributes to the advancement of autonomous UUV control methods and can be used in designing advanced robotic systems for marine research, monitoring, and underwater technological operations.

This work is devoted to the study of acoustic phonon scattering in aluminum nitride (AlN) thin films grown by magnetron sputtering with an emphasis on their potential application as piezoactive layers for microwave resonators. The main objective of the work is to establish a correlation between the data obtained by various analytical methods, including Mandelstam-Brillouin scattering (MBS), Raman scattering (RS), infrared (IR) and terahertz (THz) spectroscopy, as well as X-ray diffraction (XRD), to assess the quality and homogeneity of AlN films. The data analysis confirmed the high stability of the MBS peaks in the studied films. It was found that the stability of the MBS phonon peak reaches 87.6 ± 0.5 GHz, which corresponds to the literature data, and confirms the homogeneity of the films with an error of less than 1 %. The presence of a specific peak in the XRD patterns and the minimum width of the phonon peak obtained by Raman and FTIR spectroscopy confirm the possibility of using these methods to characterize such micron-thick films. Considering that the peak frequency of the phonon resonance did not change for films with a thickness of 4.5 μm, it is assumed that the analysis of the phonon line width may be sufficient to evaluate the grown films. The Raman method seems to be especially promising, which in the future can allow in situ analysis during the growth of AlN films. Thin AlN films with a thickness of less than 7 μm have the quality sufficient for the development of acoustic microwave resonators, which opens the way for the experimental creation of multilayer structures with different acoustic impedances based on the obtained data.

In this work, the interaction of terahertz radiation with thin ITO films (< 300 nm) deposited on fused silica substrates was studied. The complex refractive index of the films was measured in the range of 0.2-1.2 THz. It was found that the Drude model accurately describes the dielectric properties of the films in this region. The parameters of the model were determined by fitting the experimental data across a wide spectral range, from millimeter to visible wavelengths. A linear correlation between conductivity and thickness of the film was revealed. The result is valuable for the design of antireflective coatings for terahertz radiation applications. The studies on the effects of intense terahertz radiation with peak and average intensities of up to 2 MW/cm² and 1.2 kW/cm², respectively, showed the absence of laser-induced damage to the films and made it possible to outline the scope of ITO films' application as dichroic mirrors in transport channels for intense terahertz beams.

The paper presents the results of studies of coherent population trapping (CPT) resonances recorded in a cell with 87Rb vapors with the addition of a buffer gas under multifrequency excitation by radiation from an external cavity diode laser (ECDL). The laser diode injection current is modulated simultaneously by microwave (MW) and very high frequency (VHF) signals. It is found that for a certain range of VHF modulation frequencies, the CPT resonance amplitude is proportional to the product of the electric field strengths of the spectral components contributing to the resonance excitation. The proposed model for calculating the resonance amplitude is in good agreement with the experimentally obtained data.

The properties of the anodic oxidized Si layers implanted with CO⁺ ions at an energy of 90 keV to were studied as a function of ion dose ranging from 2.5x10¹⁵ to 3x10¹⁶ cm^-2. After the implantation, the samples were annealed at 700 ^oC for 1 hour in the N₂ ambient. Spectral ellipsometry, atomic force microscopy and Fourier transform infrared spectroscopy were employed to study the oxidized layers. The refractive index of oxidized layers was higher than that in the thermally oxidized SiO₂ and dropped from 1.58 to 1.52 as the ion dose increased from 2.5x10¹⁵ to 1x10¹⁶ cm^-2. As the ion dose increased, the absorption band corresponding to the optical absorption by CO₂ molecules grew. The refractive index of the anodic oxidized layers as a function of ion dose is discussed in the frame of the microcavity formation in the SiO₂ as result of CO₂ molecules evaporation.

Experimental data on the energy efficiency (EE) of input/output of radiation along its entire propagation path in the medium of photopolymer holographic gratings and a planar waveguide were obtained and analyzed. It was found that the main contribution to radiation power losses is made by absorption in the photopolymer medium due to incomplete bleaching of the dye during post-processing of holograms, as well as their relatively low diffraction efficiency (DE). Due to insufficient matching of the spectral characteristics of reflection holograms and LED displays, only part of their radiation power is used as a useful signal. Taking into account the obtained experimental data, the final estimate of the EE was ~ 10 % relative to the LED radiation power at the input of the entire "input/output gratings - waveguide" structure. To increase the efficiency, it is necessary to use recording media with a small thickness (less than 10 μm) and, at the same time, with a large amplitude of photoinduced change in the refractive index, which can provide the necessary DE and the degree of matching of the specified spectral characteristics, as well as reduce absorption in the photopolymer medium. In this case, the expected EE value can be ~ 40 %.

A study of the complex spatial flow of a freon jet flowing out of a long triangular cross-section channel in the laminar-turbulent transition mode was conducted. In order to obtain a detailed picture of the flow, a multi-angle measuring complex of Gilbert diagnostics was implemented based on the IAB-463M device. It was shown that the channel geometry has a weak effect on the laminar-turbulent transition scenario in the channel, with the formation of turbulent spots. It was found that when a turbulent spot hits a jet flowing out of a triangular cross-section channel, it causes turbulization and generates secondary disturbances in the mixing layer. The results may be of practical importance in CVD combustion and deposition processes.

A new method for improving the quality of images reconstructed from digital holograms is considered. It utilizes spatial subpixel shifts, i.e., shifts by a certain value smaller than the resolution provided by the recording devices. In digital holography, photodetector matrices are used as a recording medium for holograms. The resolution is determined by the type of matrices used. To obtain holograms, a camera with a photodetector matrix with a resolution of 9000 × 6752 and a single element size of 0.86 × 0.86 μm was used. The size of the matrix used was 7.7 × 5.8 mm, the spatial resolution of such devices is approximately 500-1000 lines/mm. This already makes it possible to obtain digital holograms. However, to improve the quality of reconstructed images, it is necessary to increase the hologram resolution during registration. To increase the resolution, a device for introducing a spatial subpixel shift of the photodetector matrix was used in this study. Insufficient matrix resolution was compensated for using subpixel spatial shifts. The shift was performed along the X and Y coordinates by 430 nm, which was half the size of one matrix element. The digital hologram size increased fourfold (18,000 x 13,504 pixels). Image reconstruction was performed using a fast Fourier transform. To speed up the process, a graphics accelerator was used to reconstruct images from holograms.

The kinetic physical-mathematical theory of metal creep, which accounts for thermally activated dislocation glide, is applied to describe the creep process under uniaxial tension for the EI696 steel and the EI826 nickel alloy under non-stationary thermomechanical loading conditions. The new results obtained in this work demonstrate the potential of this theory for applications in aircraft design.

The fabrication of Al-metallic glass (Fe₆₆Cr₁₀Nb₅B₁₉) composites with low residual porosity and varying component concentrations is presented. During sintering, no interfacial interactions between the composite components are observed. The hardness and thermal conductivity of the Al-metallic glass composites are experimentally determined. The experimental data are compared with values calculated using the rule of mixtures. The measured thermal conductivity of composites containing 20 and 80 vol.% metallic glass closely matches values predicted by models for parallel and series phase connectivity, respectively. The hardness values for these composites are consistent with those calculated using the Reuss and Voigt models.

An experimental setup for free circular rotation of blunt bodies about their longitudinal axis is described. A procedure for determining the roll moment in wind tunnel tests is presented. A method for determining the equivalent aerodynamic roll damping coefficient is developed, based on the fact that the viscous friction moment component in rolling bearings is independent of the axial load. For a segmental-conical body, the experimental value of the coefficient is shown to be close to the value calculated by numerical integration of the continuum equations in a quasi-stationary approximation. The proposed method can be used to determine the roll damping moment of reentry vehicles, which is necessary for solving flight dynamics problems.

Results of a combined computational and experimental study of the vortex structure in the reattachment region of a separated flow at a freestream Mach number M_∞ = 6 are presented. Three compression corner configurations are examined: a compression corner formed by two flat surfaces, the same compression corner with sidewalls, and an axisymmetric model. The compression angle is identical in all cases, equal to 30°. The model geometry is found to significantly affect the structure and parameters of the vortex flow in the reattachment region. This specifically pertains to the presence or absence of longitudinal Görtler-type wall vortices, their geometric dimensions, and the magnitude of the force and thermal parameters in this region.

The distributed receptivity of a swept-wing laminar boundary layer to unsteady freestream vortices with a longitudinally oriented vorticity vector in the presence of uniform spanwise surface undulations is experimentally investigated. Experiments are performed on a 25° swept-wing model under fully controlled disturbance conditions. Unsteady longitudinal freestream vortices are found to induce highly efficient distributed (in the streamwise direction) excitation of unsteady cross-flow instability modes at combination spanwise wavenumbers. This excitation results from vortex scattering by surface inhomogeneities. Part 1 of this study (published in the previous issue of the journal) describes the experimental approach and its theoretical justification; the experimental setup; the mean flow structure; the method of disturbance generation; the characteristics of freestream and surface disturbances; experimental evidence for the high efficiency of the investigated receptivity mechanism; the important role of longitudinal wavenumber resonance in exciting the most amplified cross-flow instability modes. Part 2 of this study (the present paper) presents the experimental determination of the amplitudes and phases of the distributed vortex-roughness receptivity coefficients as functions of disturbance frequency and spanwise wavenumber. Receptivity coefficients responsible for cross-flow wave excitation on a smooth surface are also obtained, and the relative efficiencies of the distributed vortex receptivity and vortex-roughness receptivity mechanisms are compared. The results are further compared with those previously reported for distributed vortex receptivity on a smooth surface.

The feasibility of controlling turbulent incompressible flow over an asymmetric Clark Z airfoil is investigated using two passive techniques. Firstly, air bypass through perforated surface regions from a high-pressure to a low-pressure area. Secondly, an external pressure flow introduced through the leading edge of a wing and subsequently diverted to its lower surface. The study is conducted over a chord within a Reynolds number range Re_c = (0.40-1.28) × 10⁶ and angles of attack from -6° to 6°. The examined control method exhibits an ambiguous effect, which depends significantly on the length and chordwise position of the mass-transfer region, the angle of attack, and the Reynolds number. Under certain conditions, however, a reduction in airfoil drag of 4-5% and an increase in lift are achieved, leading to an improvement in aerodynamic efficiency.

Results of the first combined computational and theoretical study of the effect of flow-aligned rectangular depressions (slots) on the surface of a flat plate on boundary-layer stability at a freestream Mach number M_∞ = 2 are presented. Slots of various depths (Reynolds number 0 ≤ Re_h ≤ 5400) and small width relative to the instability wavelength are considered. The mean flow is obtained using the FlowVision computational fluid dynamics package. Linear stability theory calculations reveal that increasing slot depth shifts the frequency range of boundary-layer instability toward higher frequencies. The spatial growth rates of the disturbances become lower than those for a boundary layer over a smooth surface, indicating flow stabilization.

The mechanism of longitudinal vortex formation in a supersonic jet issuing from an axisymmetric radial nozzle is investigated. Numerical simulations of the gas flow reveal that these vortices arise when gas flows from the prechamber into the inlet channel through a series of holes in a direction perpendicular to the axis of symmetry of the radial nozzle. The resulting vortices are then transported by the gas flow from the inlet channel into the radial nozzle and subsequently into the supersonic jet emanating from the nozzle. The numerical results are in satisfactory agreement with experimental data.

An original method for constructing a model porous medium is proposed. The approach is based on a well-known and widely used capillary model that accounts for pore-size distribution. The porous medium model is constructed by dividing the medium into thin layers perpendicular to the assumed flow direction, with capillary segments whose characteristics are determined using standard core analysis methods. The layers are probabilistically interconnected, forming parallel capillaries with variable cross sections. Within the inertialess flow approximation, the effective diameter of the capillaries is calculated. A pair of connected capillaries of different diameters is then replaced by a new capillary with this effective diameter. After repeating this operation iteratively, the original porous medium is represented by a bundle of parallel capillaries of uniform diameter. The theoretical aspects of the method are described, the adopted assumptions are substantiated, and the limitations of the model's applicability are identified. Results of absolute permeability calculations for two rock samples are presented and compared with those obtained using the classical capillary model. The proposed model is shown to provide a more accurate match between calculated and experimental data.

A method for controlling aerosol dispersion by applying ultrasonic vibrations of varying intensity is theoretically substantiated. Depending on the frequency and intensity of the ultrasonic field, either particle coarsening or fragmentation can be induced in the gas-dispersed system. A mathematical model for the coagulation and fragmentation of aerosol droplets in an ultrasonic field is developed. For the first time, a coagulation-fragmentation criterion ( t_CF ), defined as the ratio of the characteristic times of these two processes, is proposed. An expression for the critical particle diameter at which the characteristic times are equal ( t_CF = 1) is derived.

The distributions of velocity fluctuations in a Hagen-Poiseuille flow are obtained experimentally for various Reynolds numbers and pipe diameters. The longitudinal velocity fluctuation distribution is found to peak on the axis and to be independent of the Reynolds number. As the Reynolds number increases, the turbulence intensity in the tube decreases, while the root-mean-square value of the fluctuations increases. Velocity fluctuations (less than 2%) in the Hagen-Poiseuille flow are shown to have virtually no effect on the jet outflow from long pipes.

Full Navier-Stokes equations are applied to identify two branches of viscous flow regimes in the form of steady traveling waves between two smooth surfaces. The existence domain of the new solutions is determined on the parameter plane (wavelength and Reynolds number), and the flow regimes corresponding to one of the branches are shown to be unstable. Stable regimes exist over a wide range of Reynolds numbers, starting from values significantly lower than the Reynolds number at which the linear stability of the base steady-state solution is lost. The main wave characteristics of the new-type solutions are calculated. Achieving these solutions requires a pressure drop substantially greater than that needed for the base steady-state solution, while also resulting in enhanced heat transfer from the walls.

A numerical study of the effect of a perturbation generated by a vortex-generator fin on the local flow structure and turbulence of a bubbly flow in a planar channel behind a backward-facing step is performed. An Eulerian approach is employed to describe the flow dynamics and heat and mass transfer in both the carrier gas and dispersed phases. The problem is solved using the Reynolds-averaged Navier-Stokes equations, modified to account for the presence of bubbles. The influence of air bubble concentration, initial bubble diameter, and vortex generator height on the turbulent flow structure and the length of the separation region is investigated. The presence of the vortex-generator fin induces a significant (twofold) increase in the turbulence level in both single-phase and two-phase bubbly separated flows. The fin is found to exert a substantial effect on turbulence in the separated flow, with the turbulence level increasing by up to 60%. The addition of bubbles reduces the recirculation zone length (by 60% for ∆/H = 1/3).

A model for coupled axial-torsional oscillations of a drill string in a borehole of arbitrary profile is proposed. A numerical solution scheme is developed. A comparative analysis of the simulation results and field test data is performed. The main factors influencing the onset of stick-slip oscillations are identified as the intrinsic specific energy of rock destruction and the rotor speed. Comparison of the calculated results with field measurements demonstrates the adequacy of the model, with an accuracy acceptable for practical applications.

Results of an experimental study on the acoustoelasticity arising from the propagation of ultrasonic Rayleigh surface waves in a field of static bending stresses are presented. For a St. 20 steel specimen, the acoustoelastic effect is shown to differ under compression and tension. A calibration curve is constructed for Rayleigh surface waves, enabling their use for monitoring bending stresses-a capability not possible with bulk wave probing.

A gravity-based hydrodynamic flow loop capable of generating both steady and unsteady flow conditions is presented. The setup achieves velocities up to 16 cm/s and pressure fluctuations in a range of 60-130 mmHg within the measurement zone, enabling hemodynamic studies of virtually any segment of the cardiovascular system. For the first time, flow rate control is achieved by varying the angle at the junction of the systolic and diastolic flow circuits of the loop. Independent control of the minimum and maximum pressure in the unsteady flow is also implemented.

An experimental study of the primary and secondary unsteady instabilities of the boundary layer of a swept wing was conducted under conditions of dominant primary crossflow instability in the presence of a localized three-dimensional roughness element on the streamlined surface. Measurements were performed using a hot-wire anemometer in a low-turbulence wind tunnel at low subsonic free-stream velocity under conditions of uncontrolled ("natural") unsteady disturbances. Four types of amplified unsteady boundary layer disturbances were detected and studied in detail: low-frequency disturbances associated with primary flow instability, mid-frequency disturbances (type III secondary instability), and high-frequency disturbances (types I and II secondary instability). The properties of these disturbances were studied in detail, and an analysis of the position and shape of their localization regions in the plane normal to the wall and flow was performed relative to the layers of strong shear of the longitudinal component of the mean flow velocity along the spanwise and normal to the wall. The complex nature of the secondary disturbances is demonstrated, which is difficult to explain by the simplified concepts of the existence of z- and y-modes of secondary instability considered in previous studies.

Based on a system of gas dynamics equations for a mixture of vibrationally excited chemically reacting molecular gases, the effect of a carbon dioxide additive on the stability of a hypersonic boundary layer of neutral nitrogen on a plate was studied. Calculations were performed for five mixture composition variants. Steady-state flow parameters were calculated using a locally self-similar approximation of the boundary layer equations. Within the framework of linear stability theory, the dependences of the critical Reynolds numbers Re_δc and the laminar-turbulent transition Reynolds numbers Re_xT* on the molar concentration of the additive were obtained. In particular, for a 50% mixture, the relative increase in both criteria compared to the corresponding values for a mixture of perfect gases is approximately 53%. Moreover, the contribution of CO₂ dissociation to the shift of the laminar-turbulent transition zone is twice as great as the contribution of vibrational mode relaxation. It is shown that the obtained dependence ofRe_xT* on the molar concentration of the additive correlates with the corresponding experimental results of Professor H. Hornung's group.

The article presents the results of hot-wire measurements of the free-flow and boundary layer of a flat plate with a blunt leading edge, in the presence of an N-wave disturbance source. Based on the measurements, estimates of the cross-correlation characteristics were obtained. Based on the distribution of the mutual phases, conclusions were drawn regarding the presence of diffraction phenomena of free-flow pulsations. It is shown that, in contrast to the case with a sharp leading edge, in the case of a blunt leading edge it is not possible to reliably determine the presence of diffraction phenomena.

The flow pattern in the planar turbulent far wake past a body in a passively stratified medium is investigated by applying a mathematical model including the following features: Rodi’s algebraic approximations for Reynolds stress, the differential equation for transfer of a deficit in the mean velocity longitudinal component, the balance of the turbulence energy and its dissipation rate, fluid density deficit, vertical component of the mass flux vector, and the equation for dispersion in the turbulent fluctuations of density. The far-wake approximation is used in this problem. The paper discusses an issue of the local-equilibrium truncation taken for the two last equations. We compare the solutions of self-similar degeneration of the density field characteristics for a case of a classical turbulent wake behind a towed cylinder and for a case of momentumless turbulent wake. The results of numerical experiments were a foundation for interpreting the observed high error while using the locally-equilibrium truncation equation for transfer of the density fluctuations dispersion.

An experimental study was performed for a flow in a channel with an intermittent pattern of roughness. The influence of the relative obstacle height (ranging from 2 to 10 % of the channel height) on the turbulence characteristics and flow structuring in the channel nearwall zone was studied. The research was focused on the case of obstacles with a low height. We found that the obstacle height below 5.5 % induces a drastic change in pulsation and spatial flow characteristics; this alters the flow pattern in the separation zone and the vortex generation mechanisms. The across size of vortex behind the obstacle with a relative height of 2 % is twice as big as the obstacle height. The characteristic peak in spectra that corresponds to the vortex shedding frequency with fully developed roughness tends to degenerate with a decrease in the obstacle height. Here the key factor for vortex generation is due to vertical swing motion of the boundary for separation zone.

Methods of 3D numerical simulation were applied for evaluating the flow dynamics in the internal electrode of a plasmatron with a two-chamber design while a “cold” blowout through the electrode. This study presents spatial distributions for the gas flow velocity, turbulence kinetic energy and the pressure inside the two-chamber electrode equipped with two swirlers (they provide tangential input for plasma-forming air flow). Variations in the gas velocity for transversal cross-sections of the arc chamber are in agreement with previously published data for the case of “cold” smoke-based blowout of the two-chamber plasmatron equipped with a cylindrical electrode. It was established that the cylinder-conical shape of the internal electrode might result in a shorter initial laminar column in the electric arc; this happens due to expansion of the turbulent interval at a fixed length of the arc. Experiments in a plasmatron with an inter-electrode insert demonstrated that the cylinder-and-cone shape of the electrode causes a higher (by 30-35 %) voltage on the plasmatron as compared with the cylinder-only shape of the electrode. This is a qualitative confirmation for calculated results about a higher kinetic turbulence energy and a wider turbulent zone of the electric arc occurring in a two-chamber design plasmatron.

This paper considers a relation between the emissivity of metals from the V period of the Periodic System while melting process with thermophysical properties: surface tension coefficient (γ) and specific heat capacity (C_p). Taking the own and available experimental data and using the theoretical calculation within Foot’s approximation, we elucidated the laws of emissivity as a function of electronic stricture and interatomic interaction. It was demonstrated that a correlation between the emissivity and γ and C_p has a complicated behavior and this is dictated by general trends (emissivity increases with γ) and by a specific electron configuration for given elements. The results underline the importance of considering the periodicity and electronic configuration in forecasting the thermophysical properties of metals in the phase transition state.

An experimental study of polydisperse pulp hydrodynamics is relevant for the tasks of aluminum production. The diagnostics method of matrix electrical impedance has been developed based on the synchronous recording of the spatial distribution of parameters of the complex conductivity and dielectric permittivity of the medium at the nodes of a wire mesh. This method allows for the study of three-dimensional flows of a multiphase model. The core of the measuring system is a matrix mesh electrical impedance sensor consisting of coordinate-linked sets of conductors whose spatial intersections form the measuring nodes of the system. The tracer is a liquid with a complex electrical conductivity different from that of the main flow. During the measurements, impedances are dynamically recorded at each three-dimensional spatial node of the mesh, determining the parameters of multiphase flows. The study experimentally demonstrated the feasibility of measuring impurity propagation during mixing in liquids with a dynamic range extended to 90 dB.