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In the presented work, the process of heat and mass transfer inside an original design nozzle for a catalytic reformer of diesel fuel in a low-mass-flux mode is investigated by direct numerical simulation using Open FOAM open-source code. The main goal of a new nozzle design is to increase the rate and degree of fuel evaporation, as well as to improve the mixing characteristics of diesel fuel with superheated water vapor before the reaction mixture passes through the catalyst. Inside the nozzle, there are two regions where flows with opposite swirl directions are created; this leads to a strong velocity shear inside the nozzle, intensifying the mixing processes. Simulations were carried out in the Eulerian-Lagrangian formulation, taking into account the processes of evaporation of fuel droplets. The simulation results show that the flow at the outlet of the nozzle has a good uniformity of the mixture composition and provides a high degree of fuel evaporation at the early stages of flow development.

The present study is aimed at searching for mechanisms of wave interaction in a supersonic boundary layer on a flat plate with the flow being distorted by a streamwise disturbance generated on a sharp leading edge by a pair of weak shock waves. The space and time distributions and the frequency-wave spectra of oscillations and their wave characteristics in the linear and weakly nonlinear phases of wave train development in a nonhomogeneous boundary layer under conditions of a fixed power of the local source of controlled disturbances are analyzed. Based on experimental results, possible variants of wave interaction in a supersonic boundary layer on a flat plate in the region of the longitudinal wake generated by an N-wave are proposed.

Numerical computation of aiding mixed convection and heat transfer characteristics in a channel with a baffled heated wall is carried out in this work. The equations of mass, momentum and energy, alongside the boundary conditions, are solved by the finite volume formulation using the open source OpenFOAM^® code. Simulations are accomplished under different parameter combinations, including the Reynolds number, Grashof number, and baffle dimension. The results are presented in terms of streamlines, isotherm contours, Nusselt number, and friction factor. The results obtained revealed that the flow translates from steady to unsteady state at a relatively low value of Reynolds number. The unsteady flow behaviour contributes to improve heat transfer by disturbing the near-wall region. The augmentation of velocity and baffle dimension leads to a notable heat transfer enhancement; however, this enhancement is less sensitive to the heating intensity augmentation.

The influence of a thin layer of phase change material (PCM) on the thermal characteristics of the outer wall of a building made of lightweight thermal insulation material was studied numerically. Changes in temperature and heat flux density were analyzed for various locations of a PCM layer in the wall. It is shown that the use of a thin paraffin layer 4 mm thick in a wall made of foamed polyurethane 100 mm thick can reduce the amplitude of heat flux fluctuations on the inner surface of the wall in the summer from 2 to 13 times, depending on the PCM location. The greatest reduction is achieved when installing the PCM in the central area of the wall. Calculations show that when using a PCM in the walls of buildings made of light thermal insulation materials, a positive effect, associated with a 6-8 hour delay in the maximum heat flux entering the room relative to the maximum daily value of the outside air temperature, is observed in the summer.

The paper describes the results of an experimental study of the influence of control surfaces and fuselage on the structure of a separated flow around a model of a small-size unmanned flying vehicle with a straight leading edge of the wing. The use of oil-soot visualization and hot-wire anemometry shows that the separation region location depends on the attitude of control surfaces, while the presence of a fuselage leads to reduction of the critical angle of attack.

Supersonic underexpanded air jet modeling based on the QGD algorithm is carried out. The process of jet flow evolution and the formation of unsteady flow regions are investigated to obtain a good qualitative and quantitative agreement of the results with experimental and simulation data, known from the literature. The QGD algorithm is shown to enable studies of the structure of shock-wave cells in the initial region of the flow, and to describe the general character of the turbulent jet.

Based on observation data on typical areas of the Prioksko-Terrasny Reserve for 1999-2021, the influence of snow accumulation on the dynamics of the groundwater level was clarified with due account for the variability in air temperature and precipitation. An assessment of the spatial heterogeneity of seasonal and long-term variability in meteorological characteristics and the groundwater level was made. A regression analysis demonstrated that the snow storage has a significant influence on the long-term dynamics of the groundwater level during both the snowy season (December-April) and the maximum rise of the groundwater level (May-July). The effects of the air temperature of the cold season, duration of thaws, and the accumulated positive air temperatures during them on the groundwater level were statistically insignificant. The obtained conclusions complement the results of studies of the relationship between the variability of snow cover characteristics and the depth of groundwater under the conditions of modern meteorological regime and can be used to specify regional features of water exchange processes.

Experimental and numerical modeling of the temperature regime and the deformed state of the highway structure, which is a geotechnical system of “subgrade and the foundation of the highway made of frozen soil”, was carried out. Potential disturbances of the temperature regime are considered, and a design and technological solution for thermal stabilization of the soil foundation under the subgrade in flooded areas is proposed. It implies the use of geocontainers. To study and evaluate the temperature regime of the highway structure, a series of laboratory experiments were carried out. To take into account the viscoelastic properties of the soil in the mathematical model of the soil foundation, time functions of the relative settling of the soil foundation with geocontainers in the chosen temperature regime were obtained.

The proposed calculation takes into account the peculiarities of the operation of the heat pump as part of the surface foundation on permafrost soils, i.e., the heat flow from the heating circuit of the pump to the cooling circuit. Heat transfer reduces the conversion coefficient of low-potential heat into high-potential heat, but, unfortunately, this is ignored in well-known publications. In addition, the calculation shows a significant effect of the freon brand in the evaporation-condensation circuit of the refrigeration machine on the conversion coefficient.

Igor Emelyanovich Guryanov, Candidate of Technical Sciences, passed away on February 3, 2024, after a long battle with a serious illness. A renowned expert in the field of foundation engineering and frozen soil mechanics, he worked at the Melnikov Permafrost Institute for many years. He developed a new field in geocryology - engineering cryolithology - and authored two fundamental monographs on this very promising topic. He was a member of the International Society for Soil Mechanics and Geotechnical Engineering.