Home – Home – Jornals – Thermophysics and Aeromechanics 2019 number 5

The study is aimed at determining the position of the laminar-turbulent transition in subsonic and transonic two-dimensional boundary layers with the use of a novel software package LOTRAN 2.0 developed by the authors. The package is based on the e^N -method and employs numerical data of numerical simulations of the laminar flow performed by standard gas-dynamic software systems based on the Reynolds-averaged Navier-Stokes equations. As an example, the flow past a flat plate is considered. The good agreement of the computed and experimental data on the laminar-turbulent transition location is demonstrated. New data on the laminar-turbulent transition in the boundary layer on a flat plate for transonic flow regimes are obtained.

In the present paper, we report on the results of a study that was performed as part of the program for developing a method for calculating the flow and the mass-flow-rate coefficient in narrow cylindrical bleed channels under conditions of impingement of a thick boundary layer. For setting the boundary conditions at the inlet boundary of the computational domain, we used the pressure and temperature profiles obtained at the outlet boundary of the simulation domain for the flow around the forebody of a hypersonic air inlet. Numerical modeling of the 3D flow around that forebody was carried out in the range of Mach numbers from 3 to 6 at an angle of attack of 6°. The distributions of static pressure calculated along the symmetry plane and in the transverse direction were compared with experimental data. A satisfactory agreement between the calculated and experimental data is shown. The simulation of the flow was carried out within the framework of the Reynolds-averaged stationary Navier-Stokes equations using the k-w SST model of turbulence. The obtained distributions of flow parameters and flow streamlines have allowed us to perform an analysis of specific features of the flow structure on the forebody of the model air inlet and in a boundary-layer bleed channel. The calculations showed that, in the examined range of Mach numbers, a sonic flow in boundary-layer bleed channels could be realized to ensure a maximum rate of the mass flow of air through the channels.

On the basis of the Reynolds-averaged Navier-Stokes equations closed by the shear stress transport model with the consideration of streamline curvature, turbulent flow acceleration in the channel with inclined single-row oval-trench dimples, earlier found in the laminar regime, has been revealed. It is shown that the velocity in the flow core increases up to 1.4 times when dimples are densely packed. The influence of the dense arrangement of dimples on abnormal intensification of the separated flow in the stabilized area of the channel has been assessed. Absolute friction in the backflow zone in the dimple is found to grow up to 5.5 times compared with friction at the smooth channel wall.

The flow structure in a high-speed gas jet released from the nozzle of a promising liquid-fuel spray-type burner is studied experimentally and theoretically. The velocity distribution in a single-phase gas flow is measured by means of particle image velocimetry (PIV) at various operating parameters. Using the one-dimensional isentropic flow approximation, the gas-dynamic parameters are estimated for the characteristic operating regimes of the burner with supply of superheated water steam, as well as with air supply. With the use of the ANSYS Fluent CFD package, two-dimensional numerical simulation of aerodynamic structure of air stream from the nozzle is carried out. The results are compared with the measured velocity field and the flow pattern, typical of a supersonic underexpanded jet, visualized by the direct shadow photography method near the nozzle orifice.

A thermodynamic description of the Ranque effect is given. Inclusion of expansion and compression into the energy exchange process provides a rational explanation to the effect observed. These works are performed by small portions of the gas in polytropic processes. Rotational motion of the gas and the presence of irreversibility in the expansion and compression processes are responsible for energy separation. The mathematical model is constructed with the use of conservation laws and polytropic expansion. Optimization calculations are performed for various values of the efficiency and Mach number of the exhausting hot gas. A method of working process optimization hat can be used in practice is proposed. The efficiency of the expansion work is also determined in the course of optimization.

The paper presents the results of an experimental study of energy production in the Couette -Taylor heat generator with independent rotation of cylinders: the system is applied to solving the problem of direct conversion of wind energy into thermal energy. The system consists of two nested multicylinder rotors. The regimes for two counter-rotating rotors are studied. The study is focused on the rotor drag torque and the heat power of the generator as a function of the relative angular velocity of two rotors at a fixed viscosity of the working liquid or as a function of the working liquid viscosity at a steady relative angular velocity of two rotors. Representing of this multicylinder design of the heat generator to a form of a single equivalent annular channel between two rotating cylinders allows generalization of experimental data for the law of the drag torque and specific heat power as a function of the Reynolds number. This generalization offers a possibility of developing engineering methods for calculating the thermal parameters of various systems for fluid heating.

In this study, the effects of different thermo-chemical models on the macroscopic parameters of the flow behind a strong shock wave have been examined. The effect of the geometric average temperature proposed by Park and the effect of the electronic energy are also presented, and two CVD vibration-dissociation coupling models including those of Park and Kuznetsov are also examined and used for comparison. The Park93 chemical kinetic model with 11 species and 49 elementary reactions was used to describe the non-equilibrium air chemistry. The energy exchange model between translational and vibrational modes is described by the Landau-Teller formula, where the species relaxation time is based on the Millikan-White formula including Park’s high-temperature correction. The theoretical model consisting of the Euler equations supplemented with the equation of molecular vibration and the equations of chemical kinetics using a two-temperature model (translational-rotational temperature and vibrational-electron-electronic temperature) is discretized by a finite difference scheme. Good agreement is found for the relaxation zone between the present results and those obtained by Panesi for the two trajectory point (1634 s and 1643 s) for the FIRE II reentry capsule.

The results of numerical simulations of a jet discharging from a narrow slit at low Reynolds numbers Re are presented. A comparison with the data of laboratory experiments is performed, and it is shown that steady numerical solutions with increasing Re transform into unsteady solutions with self-excitation of sinusoidal instability. Lateral oscillations are superimposed at the inlet section, and their influence on the jet behavior is studied.

The theoretically calculated dependence of the sizes of the main and satellite droplets on the dimensionless wave number of the perturbation of the surface of the Newtonian fluid jet is proved experimentally. It is also shown that an increase in the fluid viscosity significantly changes the dynamics of development of capillary waves in the jet and the mechanism of formation of satellite droplets.

Chain branching and heat release processes and their influence on the burning velocity of pre-mixed rich and near-stoichiometric flames of methanol with air were studied by numerical simulation and sensitivity analysis. The phenomenon of super-adiabatic temperatures in these flames due to the kinetic mechanism of methanol combustion was first detected. Comparison of the results of simulation of the structure of methanol and formaldehyde flames showed that the formation of water in super-equilibrium concentrations in flames does not necessarily lead to superadiabatic temperatures, as believed earlier. It was first found that decreasing the dilution of the CH₃OH/O₂/N₂ combustible mixture with nitrogen at a constant equivalence ratio enhances the superadiabatic temperature effect. According to simulation results, in a rich near-limit methanol flame, the role of the H + O₂ = О + OH and О + H₂ = H + OH is negligible due to their low rate. At relatively low temperatures, branching occurs mainly in reactions involving HO₂ and H₂O₂ peroxide compounds, whose concentration is orders of magnitude higher than the concentration of the main carriers of the chain H, O, and OH. From the sensitivity analysis it follows that the methanol flame speed positively affects mainly the reactions of the formation of chain carriers and negatively affects the reactions in which chain carriers are consumed. The stages introducing the main contribution to heat release, but not involved in the formation and consumption of radicals have small sensitivity coefficients.

A kinetic analysis of the model of oxidative conversion of methane to useful products based on a set of many possible elementary reactions that could most fully reflect the chemistry of the process and for which data on rate constants are available. The analysis was carried out numerically. Key stages of the mechanism were identified and used to predict conditions under which the process can be effectively carried out in order to obtain a mixture of methanol and formaldehyde or mainly methanol. It has been shown that high efficiency can be achieved at increased pressures of the reactive mixture due to the high methane content. The directionality of the process increases with decreasing temperature.

This paper describes the development of two simplified reduced kinetic models for high-temperature oxidation of propane, which can be incorporated into complex turbulent flame simulations. Equilibrium, 0D or 1D propagating premixed flames and 2D co-flowing laminar jet flames, with or without preheating, attached or lifted, are computed during the iterative optimization process. Accompanying computations with the USC-II mechanism, as well as available experimental data are exploited for validation. Comparisons demonstrate that these reduced kinetic models ensure satisfactory agreement with data over the investigated parameter space.

A new method of initiation and effective burning of kerosene at supersonic velocities of the flow in a constant-section channel is considered as applied to combustion chambers of variable geometry. The regime of intense combustion occurs due to an external action of a package of gas-dynamic pulses with the energy varying with time. It is experimentally observed that this regime is retained if the action is terminated after the combustion process is organized in the expanding part of the combustor. It is demonstrated that the proposed method can be applied at flow temperatures and high velocities at which kerosene combustion is impossible without special tools for flame stabilization.

The boundaries of stable combustion in a flow of an air suspension of aluminum particles in a wide range of changes in an excess air coefficient (0.1-2.0) are experimentally determined. A characteristic feature of the dependence of a flame blowoff velocity on the excess air coefficient is revealed: the dependence has two maxima. Taking into account the principle of the flame stabilization mechanism, based on the equality of the flow velocity at which the flame is blown off to the flame front propagation velocity, it is concluded that there are two maxima in the dependence of the front velocity on the excess air coefficient, which correspond to the maximum values of heat release and combustion temperature of the air suspension of aluminum particles with an air excess coefficient of 0.2 and 1.0. Previously, these maxima were obtained by other researchers in thermodynamic calculations.

Combustion of a Ca-FeF₃-Fe model system is under study. It is shown that the combustion front propagation in the Ca-FeF₃-Fe system is focal. The foci of ignition of calcium particles arise ahead of the front, followed by the expansion of the reaction zone until the foci completely merge with each other and with the formation of new centers of ignition in the heating zone. The dependences of the temperature and the burning rate on the degree of dilution with iron and pressure in the system are presented. Thermodynamic calculations are performed, and the calculated and experimental data are compared. Under the general tendency of an increase in the burning rate with increasing pressure, its decrease was found to be associated with the vapor - calcium metal liquid phase transition.

The critical ignition parameters of an air suspension of promising energy-intensive compounds of MgB₁₂, AlB₂, ZrB₂, TiB₂ metal borides and the mechanical mixtures of initial components, which simulate the composition of compounds, are experimentally studied. It is established that magnesium borides ignite at temperatures much lower than those for boron, which indicates the active role of magnesium in the ignition process. For other borides, the ignition temperatures are close to those for boron, i.e., the governing factors are the diffusion of oxygen through a liquid boron oxide film and the oxide evaporation rate.

The standard enthalpies of formation were experimentally measured for four compounds: 4,6-diazido-N-(2,2,2-trinitroethyl)-1,3,5-triazine-2-amine, 6-azido-N², N⁴-bis(2,2,2-trinitroethyl)-1,3,5-triazine-2,4-diamine, 6-azido-N², N⁴-dinitro-N²,N⁴-bis(2,2,2- trinitroethyl)-1,3,5-triazine-2,4-diamine, and N²,N⁴, N⁶-trinitro-N², N⁴, N⁶-tris(2,2,2-trinitroethyl)-1,3,5-triazine-2,4,6-triamine - 690.1 ± 5.9, 326.2 ± 13.6, 630.1 ± 6.1, 415.9 ± 9.3 kJ/mol, respectively. Based on these values, the energy equivalent of replacing the hydrogen atom and the azido group by trinitroethylamine and trinitroethylnitramine groups in triazine and azido-substituted derivatives of triazine. Calculations have shown that 6-azido-N², N⁴-dinitro-N²,N⁴-bis(2,2,2-trinitroethyl)-1,3,5-triazine-2,4-diamine, and N²,N⁴, N⁶-trinitro-N², N⁴, N⁶-tris(2,2,2-trinitroethyl)-1,3,5-triazine-2,4,6-triamine with an oxygen supply ratio greater than 1.0 can be used as the basis for designing compositions with a low aluminum content and with a specific impulse of 257-260 s.

A comparative assessment of the use of various metals and non-metals as combustible components of a solid propellant containing ammonium perchlorate as an oxidizer and rubber as a binder was performed using the range criterion of an aircraft with a ramjet engine taking into account the expected completeness of combustion of individual components. The influence of the energy properties of propellants on the technical and economic indicators and flight performance of the aircraft was also taken into account. Range calculation was carried out by numerical integration of flight dynamics equations. Based on the results, a more detailed study of a number of combustible components is recommended, in particular, for the purpose of the full or partial replacement of the currently used boron in solid propellants of ramjet engines.

Results of an experimental study of heat and mass transfer and phase transitions during suppression of thermal expansion and flaming combustion of condensed matter (CM) by an example of typical combustible materials in the forest (mixtures of leaves, conifer needles, and twigs) by means of the action of a non-atomized water array at different stages of its transformations are reported. The liquid volume and the height of its discarding with respect to the CM surface are varied with allowance for the known stages of water array transformations to illustrate possible differences in the cross-sectional areas of these arrays, which determine the water-CM contact area. The characteristics of CM burning termination are obtained as functions of the height of the beginning of water array motion.

Stability of detonation waves (DWs) propagating in a plane or rectangular channel with respect to two-dimensional and three-dimensional disturbances is considered. Accepting a simple hypothesis that the most unstable mode of the linear theory continues to dominate even in the nonlinear regime, one can derive a number of fairly definite predictions of the developed DW structure from the linear stability theory. In particular, the theory predicts the number of detonation cells formed in a channel of a specified size and the cell size, the minimum size of the channel in which the multifront DW structure can still exist, and the parameters at which the number of cells changes in a jump-like manner. All these predictions are qualitatively consistent with available experimental data and numerical results.

The results of analyzing experimental data on the conditions for initiation of explosive transformation in phlegmatized HMX samples on impact with an indenter with a spherical end are presented. It is shown that the conditions for initiation of explosive transformation in a wide range of variation of parameters of the indenter and impact velocities are described by empirical equations that relate the mass-geometric parameters of the projectile with its minimum velocity, thereby initiating the explosive transformation. The resulting dependences can be used for practically analyzing the outcomes of the impact on an explosive composition, in the construction of adequate physical models of initiation, and their verification.

Examples of calculating the shock compression of liquid water and water vapor using a slightly adjusted simplified Nigmatulin-Bolotnova equation of state of water are considered. The main attention is paid to the achievement of those numerical simulation parameters (primarily, water temperature) that may be useful for synthesizing diamond from graphite. It is shown that a favorable factor for achieving a required temperature is the shock compression of a preheated layer of liquid water. It seems even more promising to use a layer of heated water vapor instead of liquid water. In the latter case, reaching the required temperatures and pressures requires a significantly lower velocity of the impactor.

The blast wave mitigation efficiency of open-cell natural rubber foam is compared in laboratory and field test setups. Blast wave mitigation is evaluated in terms of the peak overpressure and positive phase impulse. Piezoelectric pressure sensors are flush-mounted with the top surface of the base plate of the composite material in field tests and at the end plate of the blast wave generator (BWG) in laboratory tests to measure the incident pressure and pressure transmitted through the foam. The blast wave is generated by means of detonating high explosives in field tests and by bursting the diaphragm in the BWG in laboratory tests. It is observed from the test results that the pressure transmitted through foam and the corresponding impulse values depend on the shape of the loading wave and also on the test configuration used in the laboratory method. Therefore, it can be concluded that laboratory tests using the BWG only give a trend of the transmitted pressure and so can be used, at the best, for comparative evaluation of mitigation of the blast wave passing through different materials. However, actual values of the transmitted pressure and impulse can only be obtained in field tests with blast loads generated by using explosives.

The article represents studying the phenolic compound composition and content in leaves of white poplar Populus alba L., aspen P. tremula L. and grey poplar P. × canescens (Ait.) Sm. by high-performance liquid chromatography (HPLC) method. 24 compounds of phenolic nature were discovered, 7 of which are determined: coffee acid, quercetin glycosides - hyperoside, isoquercitrin, rutin and kaempferol glycoside - astragalin, aglycone - quercetin and galangin. The research showed that white poplar and aspen species are easily separated by HPLC on the composition and content of phenolic compounds. It is found that aspen spectrum of phenolic compounds is poorer in comparison with white and grey poplar samples occupy an intermediate position between white poplar and aspen on the composition and content of phenolic compounds, but the majority of hybrid samples evading towards white poplar. According to the cluster analysis, the studied samples are divided into 2 groups on the compound composition and content of phenolic compounds: only 4 hybrids are combined with aspen, the rest are grouped with white poplar, while the «pure» copies of white poplar is not stand out in an independent subgroup. The relation of objects grouping with their geographical origin isn’t revealed. The obtained results indicate that in the analyzed material there are not only the F1 hybrids, but backcrosses, which are closer to white poplar both on phenolic compounds content and morphological signs. These forms are most likely the result of grey and white poplars return crossings.

The wood of Scots pine after 100-600-year exposure to anaerobic conditions was studied. The samples were taken from the soil during archaeological excavations in the city of Veliky Novgorod. It has been established that the destruction of the secondary wall layers (mainly S2 layer) of tracheids in the sapwood and heartwood occurred after 100 and 400 years of exposure, respectively. Archaeological wood contained mineral particles consisting of water-insoluble compounds of iron and potassium. The results of thermogravimetry showed the changes in the relative content of hemicelluloses, cellulose and lignin in the samples of archaeological wood. The proportion of hemicelluloses and cellulose in wood decreased by 8-13 % and the proportion of lignin increased by 6-9 % under the prolonged exposure to anaerobic conditions (400 and 600 years) compared to the samples of 100 and 200-year exposure. This was also confirmed by chemical analysis data. The oxidative thermal decomposition of the carbohydrate complex, as well as lignin started at lower temperatures indicating lower thermal stability of the main components of the wood substance. All the studied wood samples were characterized by a significantly higher proportion of residual mass after thermal decomposition compared to sound wood. This fact also suggested higher content of mineral substances. The total thermal effect of oxidative thermal decomposition of carbohydrate and aromatic components of the wood substance was noticeably higher (13.1 and 12.6 kJ · g^-1) for the samples of 400 and 600-year exposure compared to those of 100 and 200-year exposure (8.9 and 10.8 kJ · g^-1). Mono-and sesquiterpenes were found in wood, as well as diterpen 18-norabietan, the most resistant one to biological degradation, which accounted for 30-64 % of the total content of volatile organic substances. The obtained results indicated significant changes in the composition and structure of Scots pine wood after 400 years of exposure to anaerobic conditions.

The results of the assessment of biological resources in the dumps of the Borodinskiy coal mine are given. The habitats of the same ecological capacity are distinguished according to the developed classification and interpretation of space imagery. The habitats are allocated according to the technology of recultivation (4 options), the tendency of the formation of post-technogenic ecosystems (succession - 4) and the age of the dump (formation stage - 4). For each type of habitat, the composition and productivity of grass cover, forest stand, berries, mushrooms, and game are determined. Grass cover is recommended to be used “in the lifetime state”, for example, as honey plants. Haymaking and grazing leads to the degradation of vegetation cover in mountain dumps. The zonal norm of recultivated arable land (with the application of PSP) is reached not earlier than 30 years later. The experiments with planting crops (potatoes, carrots, beets, cucumbers) showed productivity significantly inferior to the zonal norm. Forest plantations (pine, spruce) are developing the most productive first site class and superior zonal norm. The most productive are zoochorny berries plants, while it should be borne in mind that the productivity of sea buckthorn for natural reasons drops rapidly. In addition, it creates a fire-hazardous structure of forest plantations. The yield of edible mushrooms symbiotic with tree species (pine, birch, aspen) is higher than the zonal norm by an order of magnitude. At the same time, in the first 3-4 years entomoparasites do not affect the fruit bodies of mushrooms (there are no worms). The animal population of the dumps is under strong pressure from synanthropic species (raven, forty, black kites), which are attracted by the city dump. At the same time, the productivity of hunting grounds at dumps is 4 times higher than the zonal norm, perhaps this is due to the protection regime of the coalmine. The methodical techniques used and the data obtained with their help allow us to estimate the biological resources of any dumps and predict (modeling) their states. The materials should be applied in assessing the projected impact of mining and the formation of rock dumps on biological resources and planning their further economic use.

An analysis of a numerous official documents and publications reveals a serious crisis of forest management in Russia. Collapse of the forest economy has resulted from shocking changes at the end of the 20^th century and accepting a new Forest Code, approved in 2006, in which any reference to forestry disappeared. Forest management paradigm, defined by the Forest Code ideologues, will lead inevitably to the Russian forest fund degradation. Meanwhile, forestry is a productive industry, which follows market rules. For this reason, forest management should be reconstructed in Russia. A principle of forestry revival will be impartial ecological and market economic assessment of forest resources, which would be instrumental in transition of the subsidized scheme of forest management financing to a system that would provide rational forestry and a profit. Forestry comprises an inseparable triad: forest inventory, forest economics, and forest management. It is within this triad that more specific issues of rational forestry and sustainable forest use are to be solved. When state-owned forests are under market conditions, it is impermissible to sell forest resources priced below cost of their production. In view of this, market transition of forest use is crucial to establish payments for standing timber based on rental income. This will guarantee the financing of reforestation as well as assignments to the budget at the different levels. Chief reorganization objective of forest management in Russia is outlined as follows: ensuring economic efficiency of the forest sector; sustainable use of forest resources and reforestation; forest conservation for future generations.

Values of forest inventory indicators are the result of cause-effect relationships of stands with environmental factors. Forest soils, along with the amount of heat and moisture, are the main components of forest vegetation conditions. The fertility of forest soils therefore can be evaluated (measured) by means of forest inventory parameters. The regression equations are formed. As a function, the site productivity class (bonitet) of the stand is used, as an independent variable, the indicator that quantifies forest vegetation conditions. The data of mass forest inventory - the description of forest inventory compartments--contain all the information necessary for the formation of equations. The description of the section also contains soil characteristics, including the soil name (type). We can write down: B_s = f ( S ), where: B_s is the bonitet class of the stand, depending on soil fertility; S is an indicator of forest vegetation conditions. As an indicator of forest conditions, the d / d ₀ ratio was previously proposed, where: d ₀ = f ( h ); d , h - diameter and height of the main tree species of the stand (Farber, 1997). In general, the advantage is of an indicator that varies less than the others. Therefore, as a measure of forest vegetation conditions in the work, the ratio of heights S = h/h ₀ is used. In this case, the averaged growth line in height (regression equation, h₀ = f ( A ), where A is the stand age, years) is used as a reference point. By introducing an additional argument, the accuracy of determining h ₀ increases. The diameter is used as an argument of this kind, then h ₀ = f(d , A). The two-factor equation defines the origin in the form of a plane. The ratio of heights S = h/h ₀ is determined for each forest inventory compartment of coniferous tree stands. Next, the average S_i values for the tree species and soil names, and the total weighted average S ₀ for coniferous tree species and soil names are calculated. Thus, each soil type receives a quantitative measure. With the name of the soil in the description of the forest inventory compartment, regardless of the stand species composition and land category (stand, burn, logged area), we obtain a quantitative assessment of forest soils fertility with the ability to determine the potential tree species productivity. The paper demonstrates a map where, for the test site, the fertility of forest soils is shown by means of the values of S ₀, and the potential productivity of coniferous trees is shown by means of yield classes.

Assessment of forest regeneration using remote sensing data is a priority scientific research topic worldwide today. Threshold values for successful reforestation can be defined using multi-temporal satellite scenes and indices for analysis of vegetation on cutting and burned areas. The analysis of successful reforestation has practical value for Russian government organizations for transferring burned and cutting lands to forest cover land. The rate of reforestation depends on climate, soil conditions in the region of studies. Collection of field data and the studies were carried out in northern and middle taiga of Arkhangelsk Oblast. This territory belongs to boreal forest. Calculations of spectral indices for each research object were made using multi-temporal scenes for 20 years based on Google Earth Engine platform. Optimal spectral index was selected based on the analysis of collected data. The optimal threshold values of the index for transferring pixel of satellite imagery to forest cover land were found using this data. Optimal spectral index for transferring non-forest cover to forest cover land SWVI was selected. The optimal threshold value for transfer to forest cover land equals 80 % recovery of the index after a disturbance in forest cover. Method for transferring land to forest cover land was developed based on analysis of dynamic of the spectral index. The result was the spatial layer of transferring land to forest cover land in 2018 on the territory of Severodvinsk and Onega forestry district of Arkhangelsk Oblast.

A method of complex bioindicative assessment of life state pattern and sustainability of woody plants in greening growing under industrial pollution in urbanized areas has been developed. A wider set of indicators is used for the assessment in comparison with the well-known methods that point clearly to industrial air pollution impact: the symmetry of the crown, outer damage of the trunk and outer features of the bark and branches, crown density, premature yellowing of foliage, evidence of chemical burns on leaves and needles, evidence of damage to needles or leaves by insects and pathogens. The proposed method was tested on woody plants belonging to 8 species: Scotch pine Pinus sylvestris L., Colorado spruce Picea pungens Engelm., silver birch Betula pendula Roth, Siberian elm Ulmus pumila L., balsam poplar Populus balsamifera L., mountain ash Sorbus aucuparia L., Maack cherri Padus maackii Rupr., and dwarf apple Malus baccata (L.) Borkh., growing in greening of the city of Krasnoyarsk under conditions of technogenic pollution of various composition and intensity. Using the developed methodology, it was found that Scotch pine, silver birch, the Siberian elm and mountain ash were least tolerant to pollution from heavy traffic in comparison to the other species. Scotch pine, Colorado spruce, silver birch, Siberian elm, mountain ash and dwarf apple occurred sensitive to specific emissions from industrial enterprises, and these species might be used as indicators of industrial pollution level caused by specific sources. Balsam poplar and Maack cherri, according to the bioindication rating scale were less sensitive to industrial and vehicle pollution - these tree species can be used to create greenings in heavily polluted areas and industrial city districts and sanitary protection zones around industrial enterprises. The developed method can be recommended for practical application in the field of green construction and environmental monitoring in urbanized areas.

The growth rates by average diameter of different types of conifers forest stand aggregates are analyzed in the paper. Three predominant Siberian stone pine Pinus sibirica Du Tour forest types have been studied. It was found that their growth is essentially different. The growth rate of the Siberian stone pine stand of green moss-red bilberry (Pinetum sibiricae vacciniosum) forest type is especially impressive. The Siberian stone pine stand of bergenia (Pinetum sibiricae bergeniosum) forest type shows the lowest growth rate. An intermediate place occupies the Siberian stone pine stand of low herb-dwarf shrub (Pinetum sibiricae nanaherbosa-fruticosum) forest type. Two types of the Siberian stone pine stand are remarkably growing up to 140-200 years. It has been revealed that standard yield tables for different age generations are not stable models. In the Siberian fir Abies sibirica Ledeb. Stands, low growth rates are registered at bergenia (Abietum sibiricae bergeniosum) and mountain rocky (Abietum sibiricae montani-lithosum) (due to severe site conditions) forest types, but stands of gramineous-herbaceous (Abietum sibiricae poacea-geteroherbosum) forest types grow well up to 100-140 years. The Siberian spruce Picea obovata Ledeb. stands of high (wide) herbaceous (Piceetum sibiricae latiherbosum) forest type grow intensively up to 130-160 years, and have principal water conservation value. The pioneers of alpine zone - forest types of mountain pine Pinus pumila (Pallas) Regel stands (Pinetum pumilae montani-lithosum, var. fruticosum) grow slowly in severe conditions of highlands, but their principal role is the stabilization of mountain ecosystems. Mutual comparison of all types of coniferous stands of the woodland shows the better than average growth of the Siberian stone pine and the Siberian spruce stands, and worse growth of the Siberian fir and mountain pine stands. Comparison of average diameters of the Siberian stone pine and the Siberian fir stands with similar characteristic for different mountain regions of Siberia according to the yield tables have been done.

Every year in Siberia, there are thousands of forest fires that damage forests on huge areas. The main part of fires occurs in pine forests. In this regard, the paper discusses the features of post-fire regeneration in pine forest, depending on the fire intensity and the time after the fire. The dynamics of the number, growth and viability of natural regeneration of pine after fires in the pine forests of the southern and middle taiga were evaluated. The dependence of the number of young growth of the duration of the period after the fire exposure, which is particularly marked after high-intensity fire, a correlation coefficient of 0.81. A close relationship between the amount of undergrowth and the intensity of fire, the correlation coefficient 0.82. In the pine forest after fires of renewal takes place without a shift in the species with satisfactory performance. After low-intensity fires, the formation of life-capable undergrowth in pine forests extends for a longer period. It is established that at the initial stage of post-fire succession the accumulation of phytomass of natural regeneration in pine forests is also determined by the intensity of the fire and the time after the fire.

The results of the study of the quantity and state of understory of young’s regeneration after partial logging of 20 to 53 % logging intensity in mature pine forests of Pogorel’skiy pine forest are shown. Evaluation of logging operations showed that under the canopy of the remaining part of tree stands, forest site remain close in terms of the stands that are not logged. A comparative analysis of the number and life status of pine undergrowth has been carried out in pine-herbal-green moss and cowberry - herbal-green moss. Before logging, regeneration, taking into account the life condition of the undergrowth, was assessed as insufficient and partial renewal was required for regenerations. It was noted that after the first stage of partial logging in high-grade pine forests, a large number of viable young growth appeared. The number of undergrowth on the skidtaril was less compared to cut strips. However, in the runways, 4-5 years after cutting and self-seeding, there were 3 times more than in cut strips. Thus, at all 7 sites after cutting there is a sufficient number of conditionally large undergrowth, for 4 of them it exceeds the specified minimum several times. Even a weak cutting intensity of 20 % stimulated the regeneration process, but a high number of pine undergrowth is characterized by a weakened condition, which indicates a lack of lighting and the need for and the possibility of carrying out a second partial cutting. It is shown that the best preservation and subsequent renewal of pine after cutting are marked at a cutting intensity of 35 %. An increase in the intensity of cutting up to 53 % contributes to the appearance of a large number of shoots and self-seeding, while the small, medium, large undergrowth is highly damaged mechanically. We made a conclusion about the effectiveness of using the forestry measures that stimulate the forest renewal process.

In the course of the work, a study was conducted of urban forests in the territory of the Sovetskiy district of the city of Novosibirsk. There are 24 alien species of woody plants that are found in the forest areas of the residential zone and in the adjacent territories naturally. A significant part of these species appeared in the forest areas as a result of the city’s landscaping activities and the landscaping of forest parks. The identified species belong to 11 families and have a different geographical origin. The largest number of species (9) belongs to the Rosaceae family, the remaining families are represented by one or two species. Such species as Ulmus pumila , Syringa josikaea , Syringa vulgaris , Amygdalus nana , Grossularia uva-crispa , Clematis recta , Cerasus fruticose , Padus virginiana , Padus maackii , Juglans mandshurica , Ribes spicatum , Acer ginnala , Quercus robur , Berberis vulgaris , Ribes rubrum have been assigned the status of colonophytes. They are capable of self-renewing in places of drift, but are not characterized by active resettlement throughout the territory. The species Grossularia uva-crispa , Ribes spicatum and Ribes rubrum were not used in urban greening and are “runaways” from horticultural culture. Several alien species ( Amelanchier spicata , Rosa rugosa , Sorbaria sorbifolia , Ulmus laevis , Viburnum lantana ) are classified as potentially invasive plants. Acer negundo and Malus baccata , which are related to invasive species in Siberia and in Novosibirsk Oblast, are the most actively regenerating in the city forests.

The variability of the data on elemental composition of needles from the clonal population of Scots pine Pinus sylvestris L . , established on the long-term field experiment, was studied by principal components extraction from the normalized data matrix, and broad-sense heritability Н ², i.e. the contribution of clones to the total data variance was calculated both for the original variables and principal components. To find the linear combinations of variables with the highest heritability the discriminant analysis was performed. The results suggest the importance of multivariate statistics for forest genetics and selection in targeting search for genetic marker traits in the populations of woody plants, in assessing genetic differentiation among populations, identification of the best genotypes via their phenotypes, etc.

Remarkable variability in morphology of the Populus genus, as well as widely spread hybridization within the genus complicate taxa identification. Petiole anatomy plays an important role in plant taxonomic attribution and resolution of arguments in systematics. The aim of the study was to examine the petiole anatomy of P. nigra , P. laurifolia and P. × jrtyschensis to assess its potential use for taxa identification. The leaf petioles were collected from 252 individual trees in 8 populations of P. nigra , P. laurifolia and P.× jrtyschensis in the area of their natural hybridization in the basin of the Tom River in Kemerovo Oblast. Two of those 8 populations, located far from the hybridization centers, were regarded as controls to characterize parent taxa. Cross sections were made in the upper part of petioles. Then the sections were used to examine the shape of petiole cross sections, the contour of the adaxial sides, the vascular system types and lower ring shape. The petioles of trees growing far from hybridization areas were found to differ in their vascular systems: P. nigra had a linear, while P. laurifolia a high-arc-shaped one. The hybrids were found to belong to several types of vascular systems, namely intermediate, high-intermediate, linear and high-arc-shaped ones. The intermediate type of vascular system is characteristic of the most part of P. × jrtyschensis trees (78 % of the total samplings). Therefore most of them can be classified as F₁ hybrid and others - as a recombinant species. Examination of P. nigra in its natural hybridization center allowed finding an approach to the identification back-crosses. The study confirmed provides a solid basis for the identification of parent species, hybrids and backcrosses in natural hybridization areas of taxa belonging to Aigeiros and Tacamahaca sections of Populus genus.

The distribution of woody plants in terms of diameter and height was studied in virgin indigenous monodominant pine communities with the last fire of 5-130 years. High lability of morphometric characters of trees and undergrowth are shown. The types of age and vertical structure of stands are revealed. Both stepwise-different-aged and conditionally different-aged stands are formed under the influence of the pyrogenic factor. Pine stands have «regular top», «regular bottom» and «symmetrical» vertical structure. The horizontal structure of stands and undergrowth was interpreted based on the analysis of point processes using the pair correlation function. Trees are distributed on area randomly. We observed weak aggregation of young trees in stands on distances of 2-6 m. Both undergrowth and self-sowing are characterized by group distribution at small distances of up to 1-2 m. The direction of the displacement of the projections of the tree crowns centers relative to the bases of their trunks is ambiguous. The shift of the crown space towards the maximum solar radiation was detected in thinned stand with high age and big size of trees. In other types of pine forests no one-sided orientation of tree crown development was revealed. The position of the tree crowns centers on the plot shows the same spatial distribution as the base of the trunks. In phytocenoses with the presence of a young generation of trees, the effect of «convergence» of crowns is manifested due to the inclination of their thin and elongated trunks under snow pressure. It leads to a denser structure of the distribution of projections of crown centers in comparison with the position of the bases of the trunks of young trees on the plots.

Results of long-term studies conducted in flood-plain forests of Mari El Republic are presented. These forests are of vast diversity of species, age, and spatial structure of stands. It is found that there are three phytocenotical layers in the flood-plain forests, English oak Quercus robur L. and tillet Tilia cordata L. are dominants in the layers. All the tree species, with the exception of Scots pine Pinus sylvestris L. and the European white birch Betula pendula L., have an ontogenetic structure. The best vitality is typical for tillet, the worst - for the European white elm Ulmus laevis L. and English oak. The trees of Scots pine and English oak are the highest ones in the stands. High correlation between the height of trees (all species) and their diameter is revealed. It is demonstrated that there is a quantity of undergrowth in flood-plain forests, where tillet typically dominates as it is well adapted to growing under the canopy. In some temporary inundated areas, self-seeding spruce Picea abies (L.) H. Karst. and fir Abies sibirica Ledeb. trees spring up and successfully grow under the stand canopy. Young oaks, birches, and aspens Populus tremula L. grow well in the canopy openings only or after a complete death of the stand. Currently phytocenotic processes in the flood-plain forests are going with dominating positions of tillet.

The article is devoted to the formation of modern phytocoenoses of broadleaf and small-leaved-broad-leaved forests in the subtaiga subzone of the European Russia on the site of the previously existing coniferous and coniferous-broadleaf forests. The article shows the results of detailed geobotanical and silvicultural studies of deciduous forests of different rock composition, which were carried out on trial plots in the Precamsky regions of Tatarstan. In particular, species richness and specific saturation of communities, quantitative participation of species of different tiers, stands’ species composition, stock of individual breeds and peculiarities of their renewal are analyzed. An assessment of the conditions for the growth of forest phytocoenoses was carried out on the basis of the ratio of the species of different ecological-coenotic groups. Presently the vegetation of the studied area is represented by long-term and settled-secondary plant communities of lime-birch, birch-linden and linden-oak forests, which have arisen as a result of economic activity, as well as due to climate changes. In communities with a predominance of lime over a period of more than 60 years, there was a decrease in oak stocks, as well as an increase in the share of meadow species of plants (up to 25 %). Nevertheless, broadleaf forests of the hemiboreal strip in the north-west of Tatarstan retain a complex of ecological-coenotic features, which are caused by zonal and historical conditions. At the same time, the distribution of coniferous and deciduous forests occurs in the subtaiga subzone. The obtained data can serve as a basis for monitoring the transformation of forest vegetation in the zone of taiga contact, broad-leaved forests and forest-steppes.