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The ongoing global warming leads to the need for continuous monitoring of greenhouse gas concentrations and the magnitude of their fluxes. Gas exchange between terrestrial ecosystems and the atmosphere is mainly measured using eddy covariance, gradient, and chamber methods. This work compares greenhouse gas fluxes measured using the airborne eddy covariance technique and by means of the gas analysis system and meteorological sensors at the ZOTTO observatory. A description of instrument suites of the aircraft laboratory and observatory is presented. The comparison results showed that CO₂ and CH₄ fluxes measured by two different methods at the same altitudes coincide in sign, are close to each other in value for carbon dioxide, and differ by up to 2 times for methane. The results are of interest to specialists who study greenhouse gas fluxes using the eddy covariance method.

Cirrus clouds play an important role in formation of the climate of our planet, as far as they influence its radiation balance. Their study requires solving the problem of interpreting atmospheric laser sounding data, which is solved differently for clouds consisting of randomly oriented ice crystals and clouds containing layers of horizontally oriented crystals. In this article, within the framework of the physical optics method, light backscattering properties for horizontally oriented ice particles of cirrus clouds of the “plate”, “column” and “hollow column” type were numerically simulated. Simulations were carried out for particles ranging in size from 10 to 316 µm for wavelengths of 0.532 and 1.064 mm with refractive indexes for ice of 1.3116 + i 1.48 × 10^-9 and 1.3004 + i 1.9 × 10^-6. The solution was obtained for typical lidar tilt angles of 0, 0.3, 3, and 5°. The results are of interest for developing an optical model of cirrus clouds for interpreting atmospheric laser sounding data in case of cirrus clouds containing this types of particles.

The article presents statistics on the distribution of aerosol particles during the summer vegetation and winter dormancy of woody plants at the size Fonovaya observatory of the IAO SB RAS (Tomsk Region) from July 1, 2022, to June 30, 2023. The analysis of the ratios of aerosol fractions revealed a paradoxical situation, where the count concentration of aerosol particles 0.3-2.0 mm diameter turned out to be significantly higher in winter than in summer. A phenomenological model is suggested which describes this effect as a manifestation of the action of radiometric forces.

The paper presents the results of an experimental study on coolant flow patterns at the inlet section of a fuel assembly (FA) in the cartridge core of a reactor for an RITM small nuclear power plant. The objective was a study on influence of different inlet elements on the coolant axial velocity distribution. This task was performed by a series of experiments on a scale-up experimental model covering the inlet section components from the calibration washer up to the attachment unit between fuel rods and the diffuser. The model also covers the section of the fuel-element bundle between the absorbing grid and the spacer grid. This study is based on the pneumometric method for several critical cross-sections over the model length. The allocation of measuring points covers the entire cross-section of the model. The coolant flow features are visualized using digital maps for the working medium flow axial velocity in the fuel rod bundle cross-section. The experimental modeling can be useful for optimizing the hydraulic profiling of the components at the inlet of the fuel rod assembly. The set of test data can be applied for validation of the LOGOS CFD software and for adjusting the technique of heat and fluid computations for the core zones under a cell approximation.

Models of the severe-accident SAFR module used to calculate the cladding melt relocation along the fuel pin surface during its melting are presented in relation to severe accidents in fast-neutron reactors cooled by liquid metal. The choice of the basic system of equations and closing relations is presented. The models are validated based on experiments on melting and flow of cladding simulator melts. The error of calculating the cladding mass loss due to its melting and flowing along the fuel pin surface is estimated.

A density and a volumetric thermal expansion coefficient of the LiK₃Pb₄ ternary alloy (12.5 at. % Li; 37.5 at. % K; 50.0 at. % Pb) in the liquid state are measured for the first time. Thermal properties are studied using a gamma-ray attenuation technique in the range from the liquidus temperature T_L = 812 K to 990 K. The LiK₃Pb₄ solid alloy is known to be an intermetallic compound. Its thermal analysis at cooling from the liquid state carried out in this work has shown that the compound is likely formed by a peritectic reaction at 789 K. Based on the experimental results obtained, a table of recommended values for the volumetric properties of the LiK₃Pb₄ melt has been developed in the studied temperature range.

The study presents the results of numerical simulation for a process of generating the ash liquid phase zone in the aircraft engine combustion chamber. The simulation was performed for three operation modes: the aircraft enters an ash cloud while cruise flight, the aircraft exits the ash cloud during climb-out; the aircraft exits the cloud during the flight idle mode (recommended by ICAO). This study was conducted for the case of a dual-flow turbojet engine PD-14 (the mainline aircraft MS -21) under the impact from the Sheveluch volcanic ash in the air. Our simulations revealed that there are significant zones inside the PD-14 engine combustion chamber where the gas temperatures are above the meting point for volcanic ash. The high temperatures zones (creating a risk of volcanic ash melting inside the engine) account for over 54 % of the flame tube volume. Additionally, for the nominal flight mode (climb-out), the volume of ash melt zone exceeds 81 % of the total volume, and the flight idle mode provides only 25.3 % of the volume.

In the regimes of mixed convection, the Czochralski method investigates numerically the effect of a melt layer height on hydrodynamics and convective heat transfer in the range of relative heights of the heptadecane layer 0.1 ≤ H/R_С ≤ 2.0 with a step of 0.1. Calculations were performed using the finite difference method at a fixed rate of crystal rotation corresponding to the Reynolds number Re = 95, with the Grashof, Marangoni and Prandtl numbers Gr = 1215, Ma = 2930, Pr = 40.35 for the ratio of crucible radius to crystal radius R_С/R_S = 1.94. In this range of parameters, the flow has a laminar, steady and axisymmetric character. The evolution of the spatial flow shape, velocity and temperature fields, radial distributions of local heat fluxes, and integral heat transfer is studied depending on the relative heights of the heptadecane layer.

A new model of the phase equilibrium line (PEL) of methane has been developed on the basis of the Clapeyron-Clasius equation and the relations of the renormalization group (RG) theory. In contrast to the known PEL, when describing the density of a saturated liquid ρ⁺, density ρ^- and pressure ρ_s, of saturated methane vapor, a system of mutually consistent equations (CE) including those describing the saturation density line and saturation vapor line is used. These equations have a number of common parameters: critical indices, critical pressure, critical temperature T_c, critical density, as well as a series of coefficients of the average diameter model, d_f coefficient D_2β, complexes D_2β/D _1-α and D_2β/D_τ, calculated within the framework of modern RG theory for asymmetric systems. Based on the proposed approach, a methane saturation line has been developed; its average diameter in a wide vicinity of the critical point is described in accordance with the RG theory by the dependence d_ƒ=D_2βτ^2β+D_{1_α}τ^1_α+D_ττ, where τ = (1 - T/T_c). It has been established that d_ƒ = d_ƒ(T) within the framework of the proposed approach is a strictly decreasing function of temperature in the range from the triple point to the critical point. It has also been found that the derivative of the vaporization heat with respect to temperature, in accordance with the principles of thermodynamics, has a minimum in the vicinity of the triple point. Within the framework of the proposed PEL model, experimental data on ρ⁺, ρ^-, and ρ_s published by R. Kleinrahm and W. Wagner in 1986 are provided with standard deviation 0.0011 %, 0.0072 % and 0.0012 %, respectively, that is, with greater accuracy than the international equations of U. Setzmann and W. Wagner derived in 1991.

The dynamics of droplet interaction with a biphilic surface based on the lattice Boltzmann method with multiple relaxation times (MRT-LBM) is numerically simulated. The biphilic surface is a superhydrophilic circle located on a superhydrophobic plane. The paper describes various aspects of droplet spreading after its impact onto the superhydrophilic spot surface, rebound, and formation of a residual droplet for several sizes of the superhydrophilic region. Three typical regimes of droplet interaction with the biphilic surface are identified: droplet separation from the surface, transitional regime, and adhesion. Moreover, the velocity fields inside the droplet during the entire process of interaction are analyzed.