2304-9782, 2618-8686, 2405-7223 15 3 2022 1-216

RAR RUS 9-16 Blagoveshchensk State Pedagogical University Milinskiy Alexey a.milinskiy@mail.ru Blagoveschensk State Pedagogical University Baryshnikov Sergey svbar2003@list.ru Amur State University Stukova Elena lenast@bk.ru Stabilization of the ferroelectric phase of potassium nitrate in composites containing metallic microparticles In the paper, the temperature dependences of the differential thermal analysis signal, permittivity, and amplitude of the third harmonic of the (KNO3)1–х/Snx composites have been studied. It was shown that the temperature of the α → β phase transition decreased by 2 – 3 K in the potassium nitrates being parts of the composites, and the temperature of the γ → α phase transition decreased up to 360 K. This result can be explained within the framework of the Landau – Ginzburg theory, taking into account the shielding of potassium nitrate particles by tin metal particles. 10.18721/JPM.15301 537.226 ferroelectric composite permittivity phase transition https://physmath.spbstu.ru/article/2022.57.1/ 01_9-16_15(3)2022.pdf

RAR RUS 17-27 Ioffe Institute, RAS Molokov Anton antonmol@mail.ru Ioffe Institute of RAS Sysoeva Anna annasysoeva07@mail.ru Ioffe Physical Technical Institute of the Russian Academy of Sciences Naberezhnov Alexander alex.nabereznov@mail.ioffe.ru Ioffe Institute, RAS Koroleva Ekaterina e.yu.koroleva@mail.ioffe.ru Effect of interface modification by titanium dioxide on dielectric properties of sodium nitrite nanocomposite based on porous glass Dielectric properties and structure of initial nanocomposite based on porous glass with embedded ferroelectric NaNO2 and nanocomposite identical to that but having a TiO2-modified pore surface, have been studied over a temperature range 300 – 450 K (on cooling) and frequency one 0.1 – 3∙106 Hz. X-ray spectroscopy of the samples exhibited that NaNO2 was in the ferroelectric phase in both composites and the percentage of crystalline NaNO2 increased in the pores of the modified one. An increase in permittivity and conductivity was observed in the TiO2-modified nanocomposite. Two relaxation processes were identified and their nature was established. The charge polarization at the interfaces was found to make the main contribution to the dielectric response of the both nanocomposites. The DC-conductivity of both composites was estimated and its activation energies were determined. An activation energy change observed in a vicinity of 400 K was attributed to the phase transition to the low-temperature phase of NaNO2. The possibility to control the properties of nanocomposites through modifying the interfaces was shown. 10.18721/JPM.15302 538.956 nanocomposite ferroelectric sodium nitrate titanium oxide porous glass dielectric spectroscopy https://physmath.spbstu.ru/article/2022.57.2/ 02_17-27_15(3)2022.pdf

RAR RUS 28-42 STR Group, Inc. – Soft-Impact, Ltd. Borisov Dmitry dmitriy.borisov@str-soft.com STR Group, Inc. - Soft-Impact, Ltd. Kalaev Vladimir vladimir.kalaev@str-soft.com Comparative evaluation of RANS eddy-viscosity turbulence models for calculating the silicon melt convection in crystal growth systems In the paper, the results of RANS calculations of turbulent convection in silicon melt, obtained using several eddy-viscosity turbulence models, have been compared with previously published ILES eddy-resolving calculation data for similar conditions. A turbulence model was chosen for its subsequent problem-oriented modification with the algebraic introduction of factors that could produce the required anisotropy of the Reynolds stress tensor and the turbulent heat flux vector including in the Reynolds-averaged equations of momentum and energy. As applied to the problems of calculating the convection in crystal growth furnace crucibles using the Czochralski method, it was shown the expediency of taking either the one-equation k-model or the two-equation k-ε model as the initial RANS-model for modification. 10.18721/JPM.15303 532.5 Czochralski method ILES RANS Reynolds stress tensor turbulent heat transfer https://physmath.spbstu.ru/article/2022.57.3/ 03_28-42_15(3)2022.pdf

RAR RUS 43-60 0000-0002-3972-9259 Northern Water Problems Institute of Karelian Research Centre of RAS Smirnov Sergei sergeysmirnov92@mail.ru E-5484-2014 56020596900 Peter the Great St. Petersburg Polytechnic University Smirnov Evgeny aero@phmf.spbstu.ru

Russia, 195251, St.Petersburg, Polytechnicheskaya, 29

Experience of using semiempirical differential models of turbulence for calculation of liquid-metal convection in a bottom heated cylinder The paper deals with assessments of ability of the three RANS turbulence models (k-ω SST, k-ε RNG and one of the differential RSM formulations) to predict local and integral characteristics of the statistically 3D Rayleigh – Bénard liquid-metal convection with a key role of large-scale circulation (LSC). URANS-based calculations at the Rayleigh number of 106 and the Prandtl number of 0.025 have been performed for a bottom heated cylindrical container with equal diameter to height, using computational grids of varied cell sizes. The case of the slightly tilted container was considered where the LSC azimuth position being fixed. The suitability of the used turbulence models was evaluated by comparing the obtained results with the direct numerical simulation data obtained earlier for the same conditions. 10.18721/JPM.15304 536.25 Rayleigh – Bénard convection large scale circulation RANS model turbulence cylinder https://physmath.spbstu.ru/article/2022.57.4/ 04_43-60_15(3)2022.pdf

RAR RUS 61-70 Military Space Academy named after A.F. Mozhaysky Shirokova Elena shirokelen-78@mail.ru Simulation of an unsteady flow and mixing of fine gas suspension in a closed volume by the hybrid method of large particles Hydrodynamic effects of convective transport and mixing of dispersed reagents determine the efficiency of chemical reactions in some cases. The paper sets and numerically solves the problem of a pulsed outflow and mixing of gas suspension in a volume limited by walls. The initial dispersed-phase concentration at which an anomalous subsonic regime (with the shock-wave structure formation) is replaced by supersonic one (as to the velocity of the carrier gas phase) has been found. It was established that phenomena of instability development and eddying dominate for a long-time interval. The resolution of the hybrid large-particles method was demonstrated for this class of problems. 10.18721/JPM.15305 532/529 gas suspension shock-wave structure convective transport mixing hybrid large-particle method https://physmath.spbstu.ru/article/2022.57.5/ 05_61-70_15(3)2022.pdf

RAR RUS 71-82 Institute for Problems of Mechanical Engineering RAS Grigoreva Polina gpm@ipme.ru The influence of the trapping model choice on the adequate description of hydrogen diffusion into metals from external environment The paper considers the hydrogen diffusion into metals from their external environment. In order to properly describe a time-stable boundary layer (experimentally observed) with a hydrogen concentration being tens of times higher than that inside the body, the previously obtained hydrogen diffusion equation has been modified. This equation obtained from the first principles and taking into account the influence of the stress-strain state of solid on the transport process of the gas component, was supplemented with a stock term describing the diffusion with trapping modes. This modification was carried out in two ways: using the classical McNabb model and using the tensor of damageability. The boundary-value problem was solved for both approaches. The solution results were compared with published experimental data. 10.18721/JPM.15306 531, 538.93 hydrogen diffusion trap model solid boundary layer stress-strain state https://physmath.spbstu.ru/article/2022.57.6/ 06_71-82_15(3)2022.pdf

RAR RUS 83-99 0000-0003-0041-9971 Peter the Great St. Petersburg Polytechnic University Bykov Nikolay nbykov2006@yandex.ru Reconstructing the thermal process model using the time-space distributions of temperature The method of generative model design (GMD) has been applied to reconstruct the structure and coefficients of a partial differential equation describing the target’s heating and its evaporation by laser radiation. The initial synthetic data includes heating scenarios corresponding to surface energy absorption or to volume one. It was shown that reconstructing the model correctly required the use of a preprocessing technique providing the exclusion of a part of the initial data if the volume absorption took place. A modification of the method that made it possible to take into account the temperature dependence of the coefficients of the reconstructed equation was put forward. The influence of various statistical criteria used in selecting the optimal subset of elements on the accuracy of reconstructing the equation structure was discussed. The efficiency of the GMD was demonstrated for a wide range of target heating parameters and different options for setting the energy input. The possibility of model generating by noisy data was shown. 10.18721/JPM.15307 519.6 method of generative model design data-driven model heat transfer equation laser heating and evaporation https://physmath.spbstu.ru/article/2022.57.7/ 07_83-99_15(3)2022.pdf

RAR RUS 100-110 Southern Federal University Klunnikova Yulia yvklunnikova@sfedu.ru Fraunhofer SIT | ATHENE Anikeev Maxim maxim.anikeev@sit.fraunhofer.de

Darmstadt, Germany

0000-0002-2793-5717 Peter the Great St. Petersburg Polytechnic University Filimonov Alexey filimonov@rphf.spbstu.ru

St. Petersburg, Russian Federation

The thermoelastic stresses during laser annealing of titanium dioxide on a sapphire substrate In order to analyze the technique of laser annealing of titanium dioxide films on sapphire substrates and to optimize the film properties, a thermomechanical model of this technique has been considered. The model allowed us to monitor and vary the values of thermoelastic stresses in the film-substrate structures caused by changes of film annealing technological parameters such as the laser power, the film thickness, the pulse duration, the speed of laser emission, etc. The temperature field under the laser beam was simulated and then the stresses were analyzed using the thermomechanical finite element model. The simulation results showed an important role of the TiO2 film-to-substrate thickness ratio. The optimal combination of technological parameters was selected to prevent formation of cracks and other defects in the films. 10.18721/JPM.15308 621.382 film thermoelastic property laser annealing substrate numerical method sapphire substrate https://physmath.spbstu.ru/article/2022.57.8/ 08_100-110_15(3)2022.pdf

RAR RUS 111-131 Peter the Great St. Petersburg Polytechnic University Zasimova Marina zasimova_ma@spbstu.ru Peter the Great St. Petersburg Polytechnic University Marinova Alexandra sanmarinova@gmail.com Peter the Great St. Petersburg Polytechnic University Ivanov Nikolay ivanov_ng@spbstu.ru Peter the Great St. Petersburg Polytechnic University Podmarkova Anna ann.podmarkova@mail.ru Numerical simulation of turbulent airflow and heat transfer around a seated thermal manikin in the room with mixing ventilation The numerical simulation of turbulent flow and heat transfer, when air moves around a thermal manikin sitting in a model room with mixing ventilation, has been carried out. The calculations were performed on the basis of the RANS approach using the standard k-ε turbulence model. The buoyancy effects were described in the Boussinesq approximation. The obtained calculated data were close to the experimental ones, although there were local differences in the temperature distribution near the surface of the room walls. The impossibility of correct determination of the integral heat removal from the surface of the body without taking into account the radiation heat transfer was established. Along with studies in the ventilation regime with predominant forced convection, corresponding to the experiment, the characteristics of the flow and heat transfer in the free convection regime were analyzed, where the flow structure being caused by an intensive thermal plume forming above the manikin, and the temperature field being stratified in height. 10.18721/JPM.15309 532.517 ventilation thermal manikin turbulent airflow heat transfer natural and forced convection https://physmath.spbstu.ru/article/2022.57.9/ 09_111-131_15(3)2022.pdf

RAR RUS 132-142 0000-0002-6402-8112 Peter the Great St. Petersburg Polytechnic University Louksha Oleg louksha@rphf.spbstu.ru Trofimov Pavel fizmattrofimov@mail.ru 0000-0003-4047-3956 Peter the Great St. Petersburg Polytechnic University Malkin Alexander alexmalkin47@gmail.com Simulation of an electron beam in a gyrotron taking into account the cathode surface roughness and thermal effects in the electron gun In the paper, a 3D trajectory analysis taking into account the surface roughness of the thermionic cathode and thermal effects caused by its heating has been performed in the electron-optical system of a gyrotron with a frequency of 74,2 GHz and an output power of approximately 100 kW. A new approach based on the use of standard settings available in the 3D simulation software when the model parameters of thermionic emission being given, was used for consideration of the micron-sized cathode surface roughness. A comparison between the calculated and experimental data made it possible to clarify the regularities of the influence of the initial velocity spread and the change of geometry of the cathode assembly caused by its heating on the parameters of the electron beam formed in the electron-optical gyrotron system. 10.18721/JPM.15310 621.385.6 microwave electronics gyrotron helical electron beam cathode surface roughness heating https://physmath.spbstu.ru/article/2022.57.10/ 10_132-142_15(3)2022.pdf

RAR RUS 143-153 Peter the Great St. Petersburg Polytechnic University Tretyakov Artem tretartem@gmail.com E-4237-2014 12784708700 0000-0001-9050-4453 Peter the Great St. Petersburg Polytechnic University Kapralova Victoria kapralova2006@yandex.ru

Russia, 195251, St.Petersburg, Polytechnicheskaya, 29

Peter the Great St. Petersburg Polytechnic University Loboda Vera vera_loboda@mail.ru 0000-0001-7579-7577 Institute of Macromolecular Compounds Sapurina Irina sapurina@mail.ru Peter the Great St. Petersburg Polytechnic University Sudar Nikolai sudar53@mail.ru Influence of temperature on thermoelectric effect in the composite material based on carbon nanotubes and polyaniline In the paper, the effect of temperature (range 22 – 140 °C) on the power factor (PF) of composite material made of multi-walled carbon nanotubes with a 10 nm thick polyaniline coating applied to their surface has been studied. The conductivity value of the coating was varied by treating the composite with buffer solutions of different pH values. The nanotubes were randomly oriented relative to each other in the composite samples under study. It was found that the composite material where polyaniline was in an oxidized conductive form had the highest PF value. In that sample, the PF values were about 0.5 μW/(m∙K2) at room temperature and about 1 μW/(m∙K2) at 140 °C. 10.18721/JPM.15311 53.043 thermoelectricity polyaniline nanotube Seebeck coefficient conductivity buffer solution pH value https://physmath.spbstu.ru/article/2022.57.11/ 11_143-153_15(3)2022.pdf

RAR RUS 154-168 Peter the Great St. Petersburg Polytechnic University Pashkovsky Dmitry mr.vivivilka@icloud.com 0000-0003-0376-4463 Institute for Problems of Mechanical Engineering RAS Frolova Ksenia fkp@ipme.ru 0000-0002-5173-3218 Institute for Problems in Mechanical Engineering RAS Vilchevskaya Elena vilchevskaya_en@spbstu.ru Effective diffusion properties of a polycrystal The paper deals with the calculation of polycrystalline material effective diffusion coefficients. The polycrystalline material has been simulated by two-phase composite consisting of matrix and spheroidal inhomogeneities. The Mori – Tanaka scheme was used to account interactions between inhomogeneities. The proposed simulation took into account the effect of segregation as well. The paper put forward two models to describe the polycrystalline material. The former considered grains to be inhomogeneities, and grain boundaries to be a material matrix. The latter, in contrast, did the grain boundaries to be inhomogeneities, and the grains to be a material matrix. The simulation results were compared with experimental data. The importance of taking into account the segregation parameter when calculating effective diffusion coefficients of polycrystalline material was shown. 10.18721/JPM.15312 536.2 two-phase composite polycrystalline material Mori – Tanaka scheme effective diffusion properties segregation effect https://physmath.spbstu.ru/article/2022.57.12/ 12_154-168_15(3)2022.pdf

RAR RUS 169-184 Institute for Problems in Mechanical Engineering of the RAS Sedova Sedova Yuliya S. sedova.yus@mail.ru Institute for Problems in Mechanical Engineering of the RAS Bessonov Nikolay nickbessonov1@gmail.com.ru Institute for Problems in Mechanical Engineering of the RAS Polyanskiy Vladimir vapol@mail.ru Influence of the hydrogen skin effect on the nature of the fracture of steel specimens The influence of hydrogen saturation of steel specimens on the results of their standardized testing for resistance to hydrogen cracking has been carried out. The simulation took into account the hydrogen skin effect observed when metal samples being charged with hydrogen in various electrolyte solutions. The classical decohesion model of hydrogen embrittlement HEDE was used. It was shown that, despite the microscopic skin depth, the effect led to a dual fracture pattern, when the specimen’s cross-sectional view exhibited both a hydrogen brittleness area and a normal destruction one. The comparison of calculated results with experimental ones showed the strong influence of the hydrogen skin layer on the results of standardized metal testing. This skin effect plays a significant role in the destruction propagation over a metal sample and should be taken into account when conducting industrial tests, simulations and experimental studies. 10.18721/JPM.15313 539.561 hydrogen-induced cracking decohesion hydrogen charged sample hydrogen diffusion destruction https://physmath.spbstu.ru/article/2022.57.13/ 13_169-184_15(3)2022.pdf

RAR RUS 185-200 Peter the Great St. Petersburg Polytechnic University Markvart Aleksandr markvart_aa@spbstu.ru 0000-0001-5988-1429 Peter the Great St. Petersburg Polytechnic University Liokumovich Leonid leonid@spbstu.ru Peter the Great St. Petersburg Polytechnic University Ushakov Nikolai n.ushakoff@spbstu.ru Synthesis of window functions for reducing systematic errors of multiplexed fiber-optic sensors In the paper, the systematic (bias) error of digital processing of the biharmonic signal of two multiplexed fiber-optic interferometers under spectral interrogation, when the registered spectral transfer function being processed through a discrete Fourier transform has been analyzed. The synthesis of a special weighted window function was put forward; this made it possible to reduce the systematic errors in determining the frequencies of a polyharmonic signal without a significant increase in the random (noise) error. The effectiveness of this approach was proven through numerical simulation and experimentally by comparison with the error when using standard Dolph – Chebyshev window. The proposed approach can be applied in any problems related to the estimation of frequencies and phases of polyharmonic signals. 10.18721/JPM.15314 535.3, 535-15, 535.417 harmonic analysis discrete Fourier transform methodological error window function interferometer https://physmath.spbstu.ru/article/2022.57.14/ 14_185-200_15(3)2022.pdf

RAR RUS 201-213 Peter the Great St. Petersburg Polytechnic University Tikhomirov Victor victikh@mail.ru

Russia, 195251, St.Petersburg, Polytechnicheskaya, 29

Functionally graded wedge weakened by a semi-infinite crack In the paper, the problem of a semi-infinite antiplane interface crack located between two functionally graded wedge-shaped regions has been considered. The shear modules of the materials’ regions are quadratic functions of the polar angle. This kind of functional inhomogeneity made it possible to express all the components of the elastic field through a single harmonic function. Using the Mellin integral transform, the problem was reduced to the Wiener – Hopf scalar equation, for which an exact solution was obtained. The influence of gradients of elastic properties of materials on the stress intensity coefficient at the crack tip and the singularity value at the angular point of the structure was studied. 10.18721/JPM.15315 539.3 functionally graded wedge antiplane interface crack stress singularity https://physmath.spbstu.ru/article/2022.57.15/ 15_201-213_15(3)2022.pdf