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A review of experimental results obtained with the participation of the authors of this article, as well as in other studies on the generation and development of localized perturbations in two- and three-dimensional boundary layers, is presented. The accompanying wave phenomena and the contribution due to the spatial-temporal deformations of the velocity field of the initial laminar flow to its transition into turbulent state in boundary layers on the surface of aircraft, including small unmanned aerial vehicles (UAVs), are discussed.

The paper presents the results of numerical simulation of starting conditions for a supersonic air intake using the bypass of part of the captured air flow through longitudinal slots. The air-intake duct consists of a tapered inlet section and a constant-cross-section throat built using flat surfaces, and it contains longitudinal bypass slots stretching along the flat bottom surface. Various types of the sectional bypass of the air flow are investigated, and the change of the air-intake-duct flow structure depending on the flow bypass mode is demonstrated. Numerical modeling of the three-dimensional flow was performed for free-stream Mach number M_∞ = 4 on the basis of Reynolds-averaged Navier-Stokes equations and the κ-ω SST model of turbulence.

The paper presents a systematic view for a swirl flow produced within a cylindrical container with fixed walls and a rotating top lid using two theoretical approaches: the lattice Boltzmann equations and Navier-Stokes equations. The flow modes for this confined liquid flow were tested as functions of two parameters: Reynolds number and the cylinder height to radius ratio. The lattice convergence of both solutions was analyzed. The simulation data exhibit compliance between these two variants and with the available experimental data, including the case of the development of recirculation flow at the cylinder axis (which corresponds to the event of vortex breakdown).

A model of a thermochemical plume in the subduction zone is presented here, based on experimental modeling and theoretical analysis, as well as geological and geophysical data. A thermochemical plume originates at the boundary between the upper and lower mantle when a chemical additive is present in the crustal layer of the subducting oceanic lithospheric plate, which lowers the melting point of the crustal layer substance. The structure of thermal gravitational flows in the plume conduit melted out in the crustal layer was established due to experimental modeling. The heat power at the plume base and the heat power transferred by the plume conduit to the surrounding mantle were determined. The depth of location of a primary magma chamber, from which the thermochemical plume originates and rises to the surface of the continent, where the volcano is formed, was determined depending on the crustal layer thickness, the rate of subduction, and the angle of subducting lithospheric plate inclination. The primary magma chamber is formed in a region where the rates of subduction and melting of the crustal layer are equal in magnitude and directed oppositely. A model of the origin of a thermochemical plume on the primary chamber roof is presented, and the conditions of the plume conduit outcrop are determined. Based on theoretical modeling, geological and geophysical data on the depth of the primary chamber origin, the thermal and hydrodynamic conditions for the existence of a thermochemical plume incipient from the primary chamber and responsible for volcano formation on the surface were found.

The results are reported on the study of burning titanium particles with the diameter of 200 - 550 µm while free fall in air. Video with the rates of 25 and 500 fps captures the particle trajectories. The mathematical procedure for averaging of particle trajectories was developed. The trajectories can be classified into classes with the particle size variation within each class about 20 - 30 µm. The evolutions of particle coordinate x(t) and particle velocity v(t) as functions of time t (until the event of particle fragmentation) were presented as generalized functions for each of the size-classes. The comparison of empirical curves x(t) and v(t) with the analytical solutions for this problem about a spherical particle motion under gravity and aerodynamic drag forces gives the effective aerodynamic drag coefficient for a burning-in-air titanium particle in the format C_d = A /Re, where Re is the Reynolds number. For the particles within the tested size range, the parameter А is independent of the particle diameter and equals about 61 ± 2 for the particle motion with the Reynolds number varying from 1 to 10. If we take the aerodynamic drag coefficient C_d = 61/Re and the air viscosity equal to 5,07·10^-5 Pa·s, then the motion of burning titanium particles in air can be described by the known analytical solution for a problem of spherical particle motion driven by forces of gravity and drag within the accuracy provided by the empirical equations.

Computational experiments in the field of thermal radiation emitted by combustion products of rocket engines allow tracing the effect of determining factors on the emission characteristics, which serves to plan, predict, and interpret a physical experiment. The paper considers the influence of the condensed phase (aluminum oxide particles), the gas phase and its individual components (H₂O and CO₂) on spectral and integral radiation energy flux densities and emissivity factors in various sections of the flow of heterogeneous combustion products of a model solid-propellant rocket engine (SPRE). A comparison of the emission characteristics of incomplete combustion products and combustion products is performed for the chamber and initial section of the plume of the first-stage SPRE of Trident II (D5). The calculations of spectral radiation intensity of an initial section of the plume are compared with the results of other authors.

The characteristics of a fuel spray atomized by a steam jet were studied using the method of shadow photography. The studied method of forming a two-phase flow for dispersing liquid fuel allows application of a wide range of hydrocarbons and increases the service life of the combustion equipment due to the absence of fuel spraying nozzles. Using a long-focus macroscopic lens, the dispersed composition of spent engine oil was measured at various fuel supply frequencies: 10, 25, and 40 Hz. The dispersed phase velocity was determined using the PIV-algorithms; it amounted to 60 m/s for all studied regimes. It is shown that the frequency of liquid fuel supply does not affect the size and velocity of the formed fuel droplets.

In the current study, we conducted a numerical analysis of water-TiO₂ nanofluidand entropy generation in a wavy channel under constant heat flow( q^") by using a two-phase mixture model. The analyses were carried under a laminar forced convection flow condition. Reynolds numbers (Re) are considered in the range of 50≤Re≤600, with the volume fraction of nanoparticles φ are considered in the range of 1 ≤ φ ≤ 5 %. The governing equations are solved by using Ansys-Fluent software 14.5.The validation of the outcomes has demonstrated a strong consensus between the results and the literature's data. The effect of various Re, φ, and wavy amplitudes (α) on the flow behavior and heat transfer are examined. Moreover,the distribution of the static temperature, streamlines, total entropy generation S_g,t, Bejan number (Be) contours have been presented and discussed. Results showed that the heat transfer rate improves when φ , Re, and α increase. The heat transfer is enhanced when using a wavy wall compared to a straight wall. The performance evaluation criterion (PEC) increases with φ and Re. Therefore, it is recommended to use large values for each of φ and Re in the wavy channel from engineering and economics perspectives. Concerning S_g,t, S_g,t,h Be, we conclude that these parameters decrease when φ and Re increase, except S_g,v is increased with φ and Re.

Comparative analysis of the macro and trace element composition of fruit, leaves and stems of the plants was carried out with respect to the content of mineral nutrition elements in the soils in the natural population of the Altai subspecies of blue honeysuckle (Lonicera caerulea subsp. altaica) in the local zone where disjunctive geological structures are concentrated in the valley of the Kyzyl-Yaryk river (the Altai Mountains, the North Chuya Ridge). Substantial variations of the total content of macro and trace elements Ca, Al, K, Na, Sr, P, Mn, Ba, B, Zn, Cu, Cr and Ni, the mobile forms of Ca, Sr, Fe, Mn, Cu, Cr, Ni, Co, Na in the soils and soil acidity (pH 4.5-6.7) were revealed at the regions differing from each other in the volume activity of radon emission field (262-1162 Bq/m³). Micropopulations of L. caerulea subsp. altaica at these regions differed from each other in the level of accumulation of Сu, K, P, Na, Mo, Cr, P, Sr, Si in plant organs, and in the physiologically essential ratios Cu/Zn, Fe/Mn and K/Ca. An increase in the Cu/Zn ratio in plant organs had a significant effect on a decrease in fruit size, number of seeds in fruit, their germination capacity, and an increase in the seed germination power. The seed germination power is also in significant positive correlation with the level of Ca, Mg, Cr, Cu, Sr, Pb accumulation in leaves and stems, and with the Fe/Cu ratio. The content of K in fruit is in significant negative correlation with seed germination power.

Coke formation process is studied by the example of SARA fractions - saturated (S) and aromatic (A) hydrocarbons, resins (R) and asphaltenes (A) - naphthenic and methane crude oils by means of thermogravimetry. The studied oil samples are characterized as heavy, high-sulphur, high-resin and contain large amounts of asphaltenes. They differ from each other in the content of resins, asphaltenes, sulphur, and in the yields of fractions with the initial boiling point (IBP) 360 ^оC. Thermogravimetric analysis was carried out heating the samples from 25 to 650 C at a rate of 10 C/min in argon. It is demonstrated that the yield of coke-like condensation products (coke) depends on the composition and structure of SARA fractions. During thermal analysis, the yield of coke is lower from the fractions of saturated and aromatic hydrocarbons and resins of naphthenic oil than from similar fractions of methane oil. The amount of solid products formed during thermal analysis of asphaltenes from naphthenic oil is larger than for asphaltenes of methane oil. Experimental and calculation data on coke yield from thermal analysis of model mixtures are presented. It is determined that coke formation during thermal analysis of model mixtures is not a direct function of the additive contribution from each of the components of the mixture.