bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of the properties of Ce3+-doped fluoride nanophosphors: phase composition, morphology, luminescence
Authors: Dorokhina A M , Bakhmetyev V V , Kominami H , Toru A , Hisashi M
Published: November 2021

To date, nanophosphors have found application in various fields, one of which is medicine. These phosphors were developed with the aim to become one of the components of a drug for photodynamic therapy of oncological diseases. The aim of this work was to study the effect of the duration, environment, and stabilizers of solvothermal synthesis on the microstructure and luminescent properties of the YF3:Ce nanophosphor. The solvothermal synthesis technique was carried out in three different media: water, ethanol, and ethylene glycol. The optimal duration of the synthesis was also determined (the synthesis was carried out at a temperature of 200°C for 4…20 hours). The dependence of the YF3luminescence on the phase composition and the solvothermal synthesis medium was studied. Using SEM, the morphology and particle size of YF3:Ce phosphors were studied depending on different stabilizers (polyethylene glycol, polyethyleneimine, polyvinylpyrrolidone). The luminescence intensity of YF3:Ce and Na(Y1,5Na0,5)F6:Ce samples was compared.
Predictor of reliability indicators for nanoelectronic heterostructure devices with transverse current transfer under conditions of limited experimental information based on Bayesian inversion
Authors: Vetrova N A , Filyaev A A , Shashurin V D , Luneva L A
Published: November 2021

Predictor of the reliability indicators of resonant tunneling diodes with a generalization of the methodology for nanoelectronic heterostructure devices with quantum confinement and transverse current transfer has been developed. The advantage of the developed software is the possibility of interactive input of additional experimental information for further calculation of point and interval estimates of the reliability indicators of semiconductor devices using Bayesian inversion, which allows predicting these indicators under conditions of limited experimental information.
Methods and facilities of the automated control for thin film indicators
Authors: Maksimova O V , Nikolaev P V , Moiseenko S V , Belyaev V V
Published: November 2021

The algorithms, methods for measuring the structure parameters of thin-film electroluminescent indicators are studied. The algorithm for determining threshold voltage and plotting current – brightness characteristics was created. Realization of this algorithm accelerates process of monitoring of parameters by production known and development of new exemplars of indicator technique on the basis of thin-film electroluminescent indicators. The main aspects of a comprehensive approach to problem solving of automation of process of measurement of values of parameters of structures of thin-film electroluminescent indicators were designated, features of functioning of thin-film electroluminescent indicators as a basis of formation of structure of the device of the automated testing are considered, automation of processing of results of an experiment at the level of the software is described. Key parameters of indicators are determined, problems of automation of measuring processes are formulated, and the algorithm of determination of the threshold voltage and creation of voltage-brightness characteristic of the thin-film electroluminescent indicators in the automated mode is developed. The ideas explained in this article allow formulating the requirement specification on development of the device of the automated measurement of parameters of thin-film electroluminescent elements and also its constituents and the software.
Protection from electromagnetic pollution by using metal based shielding materials
Authors: Frah M A A , Pavlushkina T , Babinova A , Belyaev V , Makeev M , Osipkov A , Konopleva E , Zhachkin V , Usachev V
Published: November 2021

At first time a comprehensive investigation of properties of different types of filters protecting from electromagnetic (EM) radiation of to-date electronic devices for personal using – notebooks or laptops, mobile phones, WiFi devices, microwave ovens etc. has been performed for all components of EM pollution including electric and magnetic field strength and radiation power. The shielding filters were made by using different technologies including nanoparticles of transition metals implanted into glass, metal-plastic foils, glasses with different kinds of ITO coating. Values of the EM pollution reduction factors for different shielding filters types have been obtained that allow make recommendations for their practical application.
Using quantum computing to create efficient algorithms
Authors: Balaba I N , Deryabina G S , Pinchuk I A , Sergeev I V , Zabelina S B
Published: November 2021

The article presents a historical overview of the development of the mathematical idea of a quantum computing model - a new computational strategy based on the postulates of quantum mechanics and having advantages over the traditional computational model based on the Turing machine; clarified the features of the operation of multi-qubit quantum systems, which ensure the creation of efficient algorithms; the principles of quantum computing are outlined and a number of efficient quantum algorithms are described that allow solving the problem of exponential growth of the complexity of certain problems.
The resolution of a mathematically bad-defined problem in the approximation of a cellular automation by the example of the description of human states
Authors: Kalashnikov E V , Sheryomukhina A A , Filatov V D
Published: November 2021

A mathematical model describing the mutual influence of bad-defined various human characteristics is constructed. This model is described by a system of differential equations that reflect the “rate” of change in a characteristic as a function of the frequency of interaction with other characteristics. The transition from differential equations to equations in finite differences and the introduction of the von Neumann neighborhood on the resulting square space of the frequency of interaction of various human characteristics allows us to introduce a cellular automaton. The sequential execution of iterations in the cellular automaton allows to track how each of the entered characteristics depends on the behavior of other characteristics.
The organization of students’ project practice based on cloud technologies
Authors: Shevchuk M V , Gran T N , Kostyakova V G
Published: November 2021

The organization of project activities of students is discussed. Main stages of the project creation are highlighted and the activities of students at stage are presented. Main advantages of using cloud-based software in the educational environment over traditional educational software are considered. The selection of cloud services for their use at various stages of the project activity in accordance with the requirements of the educational process is presented. The proposed algorithm for organizing the project activities of students is illustrated by the description of the work on the project on the topic ”Parabola in Physics and Practical Human Activity. The presented materials were tested by the authors at the Faculty of Physics and Mathematics of Moscow Region State University during training sessions.
The effects of the axis ratio on the flow and heat transfer characteristics around a drop-shaped tube
Authors: Deeb R , Sidenkov D V
Published: November 2021

Flow and heat transfer characteristics around single drop-shaped tubes with different axis ratio (L/D) in cross-flow are studied numerically for values of Reynolds number in the range 1.3×103to 20×103. The results are obtained using the commercial software ANSYS Fluent for a two-dimensional (2D) computational domain. The axis ratio of the studied tubes is varied from 1 to 4, whenL/D=1, the tube is circular. The simulation results agree well with the available literature. The distribution of local coefficients of pressure and friction over half of the tube’s surface is plotted and analysed. It found that the drop-shaped tubes delay the separation of the boundary layer from the tube wall. The results confirm that the minimum value of pressure coefficient decreases asL/Ddecreases, and the maximum value of the friction coefficient gradually increases with the growth ofL/D.The result of the numerical simulation indicates the superior overall performance of drop-shaped tube withL/D=4 over the rest of the tubes. Correlations of the average Nusselt number and the friction factor in terms of Reynolds number, calculated by the maximum velocity in the minimum free cross-section, and axis ratios for the studied cases are proposed.
Vortex heat transfer enhancement in the separated flow near structured dimpled surfaces
Authors: Isaev S A , Popov I A , Mikheev N I , Guvernyuk S V , Zubin M A , Nikushchenko D V , Sudakov A G
Published: November 2021

The numerically discovered phenomena of abnormal enhancement of the separated flow in the inclined oval-trench dimple (OTD) and the flow acceleration in the dimpled narrow channel are substantiated experimentally. The analysis of turbulent flow around a deep OTD on the plate and on the channel wall show that within the inclination angle range from 25° to 85°, the pressure drop is seen between the zones of stagnation on the windward slope and of rarefaction in the place where a tornado-like vortex is generated. The velocity field measurements in the narrow channel with two rows of inclined OTDs at the inclination angles of ±45° and ±135° reveal that the shear flow with a maximum velocity in front of the dimple entrance is formed in the flow core. This maximum shear flow velocity exceeds the maximum velocity in the plane-parallel channel.
Determining the flow separation near a small UAV by unsteady pressure sensors
Authors: Polivanov P A , Sidorenko A A
Published: November 2021

Experimental studies of pressure pulsations on the surface of a small unmanned aerial vehicle (SUAV) are carried out in a wind tunnel. The onset of the separation flow is determined on the basis of PIV and loads measurements. It is found that an increase of pressure pulsations does not always correspond to flow separation. The paper proposes to use correlation analysis to determine the flow separation by finding large-scale coherent structures generated by the separation.
Features of air flow and heat transfer control behind a backward-facing step using a vortex generator pair
Authors: Terekhov V I , Dyachenko A Yu , Zhdanov V L , Smulsky Ya J , Sharov K A
Published: November 2021

The paper presents experimental results on the study of flow dynamics and heat transfer in the separation region behind the backward-facing step with longitudinal vortex generators (VG) installed at an angle to the flow of 30° at Re = 4000. The VG installation reduces the recirculation region and the induced longitudinal vortices and rearranges the flow structure in the separation region. The influence of a VG on the local and average thermal characteristics behind the backward-facing step is investigated and their thermohydraulic efficiency is estimated.
The effect of controlled vibrations on Rayleigh-Benard convection
Authors: Fedyushkin A I
Published: November 2021

The paper presents the results of a numerical study of convective heat transfer in a long horizontal layer heated from below with and without the vibration effect of the lower wall. The simulation was carried out on the basis of solving the Navier-Stokes 2D equations for an incompressible fluid in the Boussinesq approximation. It is shown that the influence of vibrations of the lower heated wall on the wave number of the convective flow roll structure, on the time and on the critical Rayleigh number of convection. The influence of controlled harmonic vibrations of wall on the structure of convective flow in the Rayleigh-Benard problem has been investigated. It is shown that the wave number of the periodic convective structure, the critical Rayleigh number, and the time of occurrence of Rayleigh-Benard convection under the vertical vibration effect on the horizontal layer from the lower wall are reduced.
The influence of the charge shape on heat exchange of a recessed nozzle
Authors: Benderskiy B Ya , Chernova A A
Published: November 2021

The paper deals with the numerical simulation of the flow of thermally conductive viscous gaseous combustion products in the flow paths of a power plant. The influence of the shape of the mass supply surface on the gas dynamics and heat exchange near the recessed nozzle of the power plant is investigated. The coupled problem of heat exchange is solved by the method of control volumes. It is shown that the compensator geometry determines the localization of both the topological features of the flow near the recessed nozzle and the position of local maximums of the heat transfer coefficient. It has been revealed that The use of a channel with a star-shaped cross section and a triangular form of compensator rays leads to an intensification of heat exchange processes near a recessed nozzle.
Investigating the hydraulic resistance in the flow part elements of pneumatic systems and heat exchangers
Authors: Pugachuk A S , Fominykh N F , Kalashnikova E O , Gavrilova Yu A
Published: November 2021

The article deals with the development of shell-and-tube heat exchangers for the needs of power engineering, based on additive technologies, in particular, selective laser sintering technology with new configurations of heat exchange surfaces. The role of heat exchangers in microturbines, the most common units of power plants of small distributed power generation, is considered. To intensify heat transfer and increase the efficiency of microturbines, it is proposed to use various configurations of flow channels of shell-and-tube heat exchangers made on the basis of additive technologies. Mathematical modeling and experimental study of a gas medium flow in the tubes of a heat exchanger are carried out. The dependences of the coefficient of hydraulic resistance between the surface of inlet and outlet of gas from tubes of various configurations on the Reynolds number are obtained. The results of the experiment allow us to conclude that the resistance of spiral-shaped tubes is slightly higher than the resistance of tubes with three ribs.
Numerical investigation of flows with condensation in micronozzles
Authors: Korepanov M A , Koroleva M R , Mitrukova E A
Published: November 2021

The paper considers the numerical simulation of the flow of argon with account for the condensation process in the micronozzle and behind it. To describe phase transitions, the initial mathematical model of viscous heat-conducting gas flow is supplemented with the equation of formation and growth of condensation nuclei in the flow. The developed mathematical model allows for simulating the process of gas condensation at low pressures and temperatures. It is shown that the condensate mass fraction in the flow is not less than 1% at the pressure and temperature of 5 bar and 200 K, respectively, when argon flows out of a micronozzle to the environment with the pressure of 0.01 Pa. At the nozzle exit, the size of condensed particles reaches 80 angstroms. The obtained results confirm the necessity to take into account the condensation phenomenon in micronozzle flows of inert gases.
Application of computational gas dynamics methods for calculating losses during rotation of solids in low vacuum conditions
Authors: Barkova A A , Pugachuk A S
Published: November 2021

On the basis of a mathematical model with distributed parameters, a method for determining aerodynamic losses during high-frequency rotation of a flywheel accumulator is developed. The power of losses due to friction of the rotor against the air is determined as a function of the pressure in the chamber. A comparative analysis of the aerodynamic losses under low vacuum conditions at various pressures of the working medium and the data obtained on the basis of empirical dependences and presented in the scientific literature on this topic is carried out. The maximum difference between the loss power values is no more than 25%. The data deviation decreases as the pressure in the chamber decreases.
Hydroelastic waves propagating along a frozen channel with non-uniform thickness of ice
Authors: Zavyalova K N , Shishmarev K A , Batyaev E A , Khabakhpasheva T I
Published: November 2021

Hydroelastic waves propagating along a channel covered with ice of non-uniform thickness are considered. The channel has a rectangular cross section. The fluid in the channel is inviscid and incompressible. The ice is modeled as a thin elastic plate. The ice thickness changes linearly. The problem is reduced to the problem of the wave profile across the channel, which is solved using the normal modes of an elastic beam with non-uniform thickness. It is shown that with the decrease in the change in the ice thickness, the modes approach the normal modes of an elastic beam with a constant thickness. The behavior of the dispersion relations of the hydroelastic waves depending on the parameter describing the change in the ice thickness is studied.
Magneto-convective fluctuation during downward flow of liquid metal in a heated pipe in a transverse magnetic field
Authors: Sardov P A , Listratov Ya I , Belyaev I A
Published: November 2021

An imposed strong magnetic field suppresses turbulence and profoundly changes the nature of the flow of an electrically conducting fluid. We consider this effect for the case of mixed convection flows in pipes and ducts, in which unique regimes characterized by extreme temperature gradients and high-amplitude fluctuations (the so-called magnetoconvective fluctuations) have been recently discovered. The configuration is directly relevant to the design of the liquid-metal components of future nuclear fusion reactors. This work presents the general picture of the flow transformation emerging from the recent numerical studies (DNS - Direct Numerical Simulation), illustrates the key known facts, and outlines the remaining open questions. Implications for fusion reactor technology and novel experimental and numerical methods are also discussed.
Investigating the radiation-convective heat exchange of a metal-ceramic plate
Authors: Ponomarev D A , Fedorenko V A , Naumkin V S , Lukashov V V
Published: November 2021

The paper presents the experimental data on heat exchange during thermo-cyclic interaction of a flame jet with a thermal barrier ceramic coating. Cooling due to radiant heat transfer into the environment allows organizing heat exchange in such a way that when a flow of combustion products with a temperature of 1500 °C flows onto the sample, the temperature on the surface of the TBC does not exceed 1200 °C. The thickness of TGO after 1500 thermal cycles was 9.5 microns
Experimental study of the three-dimensional flow structure in matrix channels
Authors: Philippov M V , Chokhar I A , Zolotukhin A V , Barsukov A V , Terekhov V V , Terekhov V I , Baranov I N
Published: November 2021

The article presents an experimental study of the turbulent flow in matrix channels. Using the modern optical contactless laser Doppler anemometer (LDA) method, an idea of the turbulent three-dimensional flow inside the cells of matrix channels is developed. The results of the study of the matrix channel show that the so-called vortex matrix effect is not formed. The most important factor that causes a high degree of heat transfer from the walls is the intense spiral motion between the matrix cells. The measurements also show that the effects associated with the lateral boundaries of the channel play a significant role. Based on the assumption of the decisive role of the spiral flow between the cells of the matrix channel, a formula for the integral pressure loss is proposed.
Features of device cooling in wiggler synchrotron workstations
Authors: Kabov O A , Zubavichus Ya V , Cooper K E , Pukhovoy M V , Vinokurov V V , Finnikov K A , Ronshin F V , Nikitin A A , Bykovskaya E F , Vinokurov V A , Mungalov A S
Published: November 2021

The construction of the «Siberian Photon Ring Source», the SKIF synchrotron, in Novosibirsk is underway. At the first stage, six research workstations will be created, most of the devices of which work in a high vacuum. Synchrotron radiation is generated by superconducting Wigglers for two stations. The total radiation power is approaching 49 kW, and the power density on the axis is 92 kW/mrad2. The high energy density of the beam creates quite difficult conditions for the thermal management of optical elements at the workstations. The article presents specific requirements for cooling devices, an overview of the used and promising cooling systems is made, an example of calculating the temperature, stress and strain distribution in a diamond filter with a thickness of 300 microns using the ANSYS Fluent software package is given.
Entropy change in a single Leontiev tube during energy separation of low-Prandtl gas mixture
Authors: Makarov M S , Makarova S N
Published: November 2021

The results of numerical studies of energy separation of a helium-xenon gas mixture in a single Leontiev tube with a central cylindrical channel are presented. On the basis of the simulation data, a T-s diagram for energy separation is constructed. The changes in the total temperature depending on the entropy change in the central subsonic channel and in the annular supersonic nozzle are shown.
Water movement in melting snow
Authors: Sibin A N , Papin A A
Published: November 2021

The mathematical model of water movement in melting snow is studied in neglect of deformation of the porous medium. As the mathematical model of the problem, the mass conservation equations for water, air and stationary porous skeleton of snow are used along with an analogue of Darcy’s law for water and air. Water and air are considered to be individual phases with its own filtration rate determined in solving the problem. This assumption allows constructing the closed model. The numerical test calculations are carried out. The mathematical model under study is verified using experimental data.
Solute transport in a horizontal porous layer at a high solute concentration
Authors: Evgrafova A E , Kolchanova E A , Maryshev B S
Published: November 2021

Solute transport in a porous media has not been studied systematically up to present, and there is an uncertainty about the proper governing law for describing the transport process in such media. In this study, we analyze the data of solute transport experiments in a horizontal sand column packed with uniform glass beads. Sodium chloride (NaCl) is chosen to be the tracer. A number of tracer tests are conducted to examine the transport process under different NaCl concentrations. The obtained velocity-time profiles and BTCs indicate different stages of filtering. Based on the results a possible scenario of solute transport under fixed flow rate is proposed.
Hydrodynamic structure of the flow around a stationary gas bubble in an annular channel
Authors: Kashinsky O N , Kurdyumov A S
Published: November 2021

Characteristics of the slug gas liquid flow in an annular channel were studied experimentally. The channel had the diameters of outer and inner tubes of 32 and 10 mm. The liquid flow was downward. The stationary bubble (gas slug) was produced by injecting air through a capillary tube. Wall shear stress measurements were performed by electrodiffusional technique. The measured circumferential distributions of wall shear stress demonstrated a strong non-uniformity across the channel. The highest liquid velocity was in the region of bridge streamining the bubble. The highest values of wall shear stress fluctuations are in the transition region between gas bubble and liquid bridge.
Simulation of an unstationary process of gas outflow into an open pipe area with a ring assembly filled with a liquid
Authors: Alekseev M V , Lezhnin S I
Published: November 2021

Gas outflow into a cavity with different annular assembly filled with liquid by the VOF method, supplemented by the k-ε turbulence model, is numerically simulated. Calculations are performed for three types of ring assembly. Principal scenarios of bubble growth outside the assembly and annular jets inside it are obtained. The characteristic expiration times are investigated.
Experimental study of the stratification of polydisperse emulsions in a cell with heated walls
Authors: Valiullina V I , Mullayanov A I , Musin A A , Kovaleva L A
Published: November 2021

Experimental studies of the gravitational deposition of a polydisperse water-in-oil emulsion under heat influence are carried out. When the rate of thermal convection exceeds the rate of precipitation, partial delamination of the emulsion is found to occur. The viscosity of the dispersion medium decreases with increasing temperature, which contributes to an increase in the deposition rate of water droplets in the emulsion. In the presence of a temperature difference, convective flows occur in the liquid, while the drops of the emulsion coagulate and form larger agglomerates that settle faster to the bottom of the cell.
Specificfeatures of evolution of dense atomized superheated water plumes and peculiarities of its diagnostics
Authors: Zalkind V I , Zeigarnik Yu A , Nizovskiy V L , Nizovskiy L V , Schigel S S
Published: November 2021

Experimental study of evolution of plumes of atomized metastable superheated water during its discharge through convergent-divergent nozzles is conducted. Dispersion characteristics of dense plumes in micron and submicron droplet diameter ranges are obtained. Theoretical and prediction analyses of different coagulation mechanisms in the considered two-phase flow are performed. The negligible effect of Brown-type coagulation is shown. It is also demonstrated that turbulent coagulation can change the fraction of micron-diameter droplets within 9%. In addition, for the first time, an “inertial” mechanism of coagulation is considered for the studied plumes under the conditions of plume baking in a cocurrent flow or in the ambient air. It can lead to a considerable decrease in the submicron-droplet mass fraction, which is observed in experiments even at a small distance from the nozzle cut. The predicted data are compared with experimental ones obtained at theexperimental setup.
Heat capacity of lithium tungstate single crystal by DSC calorimetry data in the temperature range of 319-997 K
Authors: Matskevich N I , Shlegel V N , Chernov A A , Samoshkin D A , Stankus S V , Grigorieva V D , Zaitsev V P , Tkachev E N
Published: November 2021

The heat capacity of lithium tungstate single crystal (Li2WO4) was measured for the first time in the temperature range of 319-997 K. The experiments were carried out by DSC calorimetry. The Li2WO4 single crystal was first grown by low-temperature-gradient Czochralski technique with weight control. The temperature dependence of Li2WO4 heat capacity in the temperature range 319-997 K was monotonic. According to results of our studies, there were no phase transitions in Li2WO4 in the investigated temperature range.
Theoretical investigation of methane hydrate nucleation kinetic from “water + gas” and “sea water + gas” mixtures
Authors: Belosludov V R , Zhdanov R K , Gets K V , Bozhko Y Y
Published: November 2021

In this work we studied transition mechanics of a dynamic hydrogen bond network of water into a stable hydrogen bond network during gas clathrate hydrate formation process. For this purpose, we used Molecular Dynamic simulation methods and a bunch of home-made programs for determining structural properties during transition process. We have found that at certain conditions the network transformation process involves the whole system from the very beginning and could be considered as a collective effect, that results in high speed of hydrate formation.
The use of a neural network for determining the temperature of a vapor film destruction in uncooled and saturated water-ethanol mixture in a cylindrical geometry
Authors: Vinogradov M M , Zabirov A R
Published: November 2021

The article presents the construction of an artificial neural network to determine the temperature of destruction of a vapor film in subcooled and saturated liquids of water-ethanol mixtures. To train the neural network, the results obtained on cylindrical samples of stainless steel, copper and nickel are used. In total, about 260 experimental points were used, which is sufficient to build a specific computational model. This article discusses a model of a neural network of the multilayer perceptron type. The trained neural network model shows a greater generalizing ability than the theoretical model for determining the temperature of vapor film destruction.
An experimental investigation of the effect of coating on heat transfer during quenching
Authors: Molotova I A , Zabirov A R , Yagov V V , Vinogradov M M , Antonov N N , Molotov I M
Published: November 2021

The work is aimed at studying the effect of galvanic nickel coating of a stainless steel cylinder on the quenching. In order to compare the results, the polished stainless steel cylinder was used as a sample. In addition, the influence of the formation of an oxide layer on the cooling process was studied. The experiments were carried out in water and ethanol with different subcoolings. The oxidized porous nickel coating led to increasing of the transition temperature from stable film boiling to intensive boiling regime. It was especially noticeable for cooling in water at high subcooling due to the higher cooling intensity caused by vapour layer thinning.
Evaporation and sparking during induction heating of metallic drops in relation to utilization of space debris
Authors: Vinogradov D A , Glazkov V V , Ivochkin Yu P , Kubrikov K G , Teplyakov I O , Sinkevich O A
Published: November 2021

The paper presents the results of primary experimental studies of intense evaporation of samples made of various metals. The heating is performed with the help of induction currents, being one of the perspective ways of heating in space. Special attention is devoted to the process of intensive small drops (sparks) ejection during heating. The obtained results are supposed to be used for the design of space debris utilization systems directly at the orbit.
Numerical modelling of melt droplet interaction with water
Authors: Yakush S E , Sivakov N S , Melikhov V I , Melikhov O I
Published: November 2021

A collapse of the vapour film separating a hot melt droplet from the surrounding water due to sudden ambient pressure rise is considered. The pressure peak causes a direct contact between water and melt, leading to significant disturbances of the melt droplet surface. Results of numerical simulations performed by the VOF method are presented. Parametric analysis of the interaction process is performed for a molten tin droplet with initial temperature of 950 K, immersed in subcooled water having the temperature of 353 K. The interaction is initiated by sudden rise of the ambient pressure to as much as 8 MPa, imitating the arrival of a thermal detonation wave, with its gradual decrease towards the initial pressure of 0.1 MPa. Simulations reveal the collapse of the vapour film, impingement of water on the droplet surface, and subsequent expansion of vapour due to rapid water evaporation. Significant disturbances of the melt droplet surface are obtained, and implications for the steam explosion problem are discussed.
Prospects for using two-phase micro-size systems for high heat flux removal
Authors: Kuznetsov V V , Shamirzaev A S , Mordovskoy A S
Published: November 2021

Heat transfer in active systems for high heat removal based on the micro-channels and hybrid micro-channel/micro-jet is considered. The application of these systems allows significantly increasing the critical heat flux for a dense arrangement of the heat stressed equipment. The characteristics of heat transfer and critical heat flux during subcooled flow boiling of water in the micro-channel heat sink and during micro-jet impingement in narrow channel are obtained. The experiments are performed for the horizontal segmented microchannels with a cross section of 340×2000 μm2 made on the top of copper target and for impingement micro-jet cooling of the copper target in the gap of 1000 μm. It has been found that, compared with impingement micro-jet cooling in similar condition, the micro-channel cooling is more effective for high heat flux removal although it creates the considerably high wall temperature.
Evaporation of aqueous solution of ethanol into an accelerated laminar boundary layer of air
Authors: Makarov M S , Makarova S N
Published: November 2021

The results of numerical studies of heat and mass transfer during adiabatic evaporation of an aqueous solution of ethanol into an accelerated steam-air laminar boundary layer on a flat wetted plate are presented. The flow acceleration is realized due to the inclination of the upper channel wall, which ensures the constancy of the Kays acceleration parameter. The dependences of the evaporation intensity of the components of solutions of various compositions are obtained for the acceleration parameter 0 and 10-6 for the flow temperature from 20 to 50 °C. A significant effect of the accelerating pressure gradient on the evaporation intensity and its weak effect on the equilibrium wall temperature are shown.
Numerical modelling of agglomeration process in a granular bed containing melting particles
Authors: Donskoy I G
Published: November 2021

The paper considers a numerical model of a flow in a porous medium containing particles of a melting component (polymer). For this, an implicit numerical method of splitting in directions is used. Calculations are carried out for two heating methods (through the side wall, or by the input gas). The simulation results qualitatively reproduce some of the experimentally observed features of the thermal decomposition of polymer-containing mixtures. The results obtained are of interest in the study of low-grade fuels processing, often accompanied by agglomeration, as well as in the development of methods by which agglomeration can be prevented.
The influence of friction on gas parameters in the minimum section of nozzles
Authors: Okhotin V S , Dzhuraeva E V
Published: November 2021

Processes of gas flow in nozzles, accompanied by the release of frictional heat, are presented in the form of polytropic processes. The polytropic process index n determines the degree of irreversibility of the gas flow process caused by the release of frictional heating. Relations are obtained to calculate the flow rate and thermodynamic properties of gas in the minimum section of the Laval nozzle and in the outlet section of the convergent nozzle at a pressure behind the nozzle less than the critical pressure. The gas calculated parameters (pressure, temperature, specific volume, velocity, cross-sectional area) in the minimum cross-section differ from the recommended values in the reference literature [1]. In particular, the gas pressure in the minimum cross section turns out to be higher than the critical pressure recommended in [1].
An evaporation flux of pure vapor in the method of lattice Boltzmann equations
Authors: Kupershtokh A L
Published: November 2021

The regularities of the evaporation flux of pure vapor in the method of lattice Boltzmann equations (LBE) are investigated. The simulations show that the mass flux during the evaporation of a flat surface is proportional to the difference in the densities of the saturated vapor at the surface temperature and surrounding vapor, which is in good agreement with the Hertz–Knudsen law. A simple method is proposed for setting the vapor flow at the flat boundary of the computational domain for the LBE method.
Numerical simulation of the process of gas outflow into an open pipe with an obstacle filled with a liquid (water, lead)
Authors: Vozhakov I S , Lezhnin S I
Published: November 2021

Submerged gas jets find a wide variety of industrial applications, and their behavior is characterized by the ratio of inertia to buoyancy and can vary from the emergence of individual bubbles to stable jets. A numerical study of the high-speed outflow of gas under a pressure of 18 MPa into a cavity with an obstacle filled with a liquid under a pressure of 2 MPa is carried out. The simulation is performed using the VOF method in conjunction with the k-ε turbulence model. The calculations are realized for three distances between the outflow hole and the obstacle: 100, 200, and 300 mm. Principal scenarios of gas jet evolution and characteristic expiration times are obtained.
On the simultaneous growth of multiple hydraulic fractures emanating from an inclined well
Authors: Valov A V
Published: November 2021

The primary focus of this paper is to investigate the interaction between simultaneously propagating multiple fractures, initiated from an inclined well. In particular, the aim is to better understand the influence of the well inclination angle on the stress shadow between the fractures and on the overall resulting geometry of individual cracks. To simplify the analysis, the paper assumes the limit of large perforation friction, which leads to a uniform flux distribution between the fractures. The mathematical model for multiple hydraulic fractures is constructed by coupling together the respective models for individual fractures, each representing a single planar fracture model. In this approach, the fracture induced stress or stress shadow from a previous time step is used as an input for a given single hydraulic fracture to propagate independently. Further, to reduce computational burden, the effects associated with tangential stresses and displacements are neglected, whereby the stress interaction between the fractures is solely described by the normal opening and the normal stress component. Numerical results are presented for the storage viscosity dominated regime, whereby the effects of toughness and leak-off are negligible. An interesting behaviour is observed, demonstrating that the well inclination angle plays a significant role on the overall fracture symmetry. For zero inclination, all the fractures are nearly symmetrical and identical. However, once well inclination is introduced, this breaks the symmetry, making a profound effect on the final result.
Evolution of artificial disturbances in a shear layer at M=1.43
Authors: Vishnyakov O I , Polivanov P A , Sidorenko A A
Published: November 2021

The evolution of artificial disturbances in a laminar boundary layer on a flat plate model in the presence of an incident shock wave is considered. The flow is supersonic with the freestream Mach number M = 1.43. The study is carried out by hot-wire anemometry. A dielectric barrier discharge is used to generate disturbances. Data on the distribution in space of the average and non-stationary components of the mass flow are obtained. Disturbances created by the discharge and their evolution along the separation zone are recorded.
Preparation of human biological fluid for studies by Laser Doppler Spectroscopy
Authors: Chubov A S , Glavny V G , Dvoynishnikov S V , Krotov S V , Meledin V G
Published: November 2021

The paper presents a method for preparing the human biological fluid by the example of urine specimen for studies by Laser Doppler Spectroscopy. The time and storage conditions of the specimen acceptable for correct research are determined. The optimal parameters for measuring and calculating dimensions - temperature, viscosity, refractive index – are identified. The need to filter samples before testing is noted. The centrifugation parameters are determined.
Calibration platform controller of the laser Doppler anemometer
Authors: Glavnyi V G , Rakhmanov V V , Dvoynishnikov S V , Krotov S V , Meledin V G
Published: November 2021

Primary standards for the unit of air flow velocity often use a Laser Doppler Anemometer (LDA) as the primary measurement standard. A rotating disc with a fixed diameter is used to calibrate LDA. The paper proposes calibration platform based on the precision mechanics of HDD disk. A disk rotation controller has been developed for the platform. Deviations of the disk rotation speed do not exceed 0.01% RMS in the range of angular speeds of 600-4800 rpm.
Development of the method of laser Doppler spectroscopy of nanoparticles in liquids and implementation of the method in the LAD-079 spectrometer
Authors: Meledin V G , Dvoinishnikov S V , Kabardin I K , Chubov A S , Bakakin G V , Kabardin A K
Published: November 2021

In this work, a method for physicochemical and biological optical studies of the nanoparticles size distribution is developed. Its implementation in the LAD-079 spectrometer is described. The distinctive features of the LAD-079 spectrometer include the following. Multi-angle parallel measurements of static and dynamic light scattering, scattering angle from 0–180 degrees. Probing at three wavelengths with the ability to analyze the polarization activity of the sample (488 nm, 532 nm, 650 nm). Programmable precision thermostat with an error less than 0.1 °C in the range 0 ÷ +80°C with the possibility of building and software implementation of the experiment plan. Robust monobloc design of the spectrometer that does not require adjustments and a special optical table. The ability to measure the size of dispersed nanoparticles in low-transparent liquids.
Study of the influence of an external flow rate perturbation on the vortex structure and heat transfer in impinging jets
Authors: Tokarev M P , Nichik M Yu , Gobyzov O A , Abdurakipov S S , Dulin V M
Published: November 2021

The study of physical processes dominating in submerged turbulent jets impinging on a wall is an important task because this configuration is utilized in various applications. The efficiency of heat transfer in this configuration has been a subject of a long-term study. Active flow control technique and the optimization of the control signal can be applied to exploit inherent flow properties to further improve the heat transfer from the wall in impingent jets. In this paper, IR-thermography and time-resolved PIV measurements are used for the diagnostics of wall temperature fields and large-scale vortex dynamics under external flow rate forcing control. It is found that the low-frequency forcing (for the Strouhal number St = 0.6) increases integral temperature on the wall as compared to the unforced case and the high-frequency forcing (St = 0.9).
Comparative analysis of working fluids for efficient waste heat recovery
Authors: Lola D Ye , Chirkov A Yu , Borisov Yu A
Published: November 2021

The paper analyzes the implementation of plants with an organic Rankine cycle (ORC) on the example of the circuit of the regenerative gas turbine unit and exhaust gas recovery system of the compressor system of the gas-compressor unit. The theoretically achievable values of power generated by the ORC-installations are determined. A criterion is presented for comparing the working fluids according to the efficiency of use in ORC-installations. To evaluate the overall characteristics of the system, the parameters of heat exchangers for air and water cooling were determined. As a result, it is concluded that the use of ORC-installations allows to utilize up to 23% of the heat of exhaust gases (convert into useful work).
Research of polymers strength properties for 3D printing under normal conditions
Authors: Volkov-Muzylev V V , Vendland L E , Borisov Yu A , Demidov A N , Fominykh N K
Published: November 2021

An article is devoted to the study of the strength properties of interlayer adhesion and determination of Young's modulus by the ball instrumental indentation method for samples, made of various plastics using additive technology under normal conditions. This production method is chosen as the most appropriate for creating lightly stressed parts of complex geometry (up to 30 MPa) in the shortest possible time. One of the possible options for such products is full-size centrifugal wheels layouts of low power gas turbine units (up to 250 kW) for testing them in model conditions. It will ensure the work of the material in the elastic zone. The samples are considered, obtained by FDM method from various polymers such as: acrylonitrile butadiene styrene thermoplastic resin (ABS+), acrylonitrile butadiene styrene thermoplastic resin with addition of carbon fibers (ABS Carbon), nylon with addition of carbon fibers (Nylon Super Carbon), polyethylene terephthalate glycol (PETG) and a compound based on polylactide (PLA HP). Plastics, made by this method, have anisotropic properties. Therefore, in this work, the strength characteristics of the test samples interlayer adhesion under tension are determined.
Generalized model of Kapitza conductance across rough interfaces
Authors: Khvesyuk V I , Liu B , Barinov A A
Published: November 2021

This paper is devoted to the theoretical prediction of the interfacial heat transfer in nanostructured materials. The main task of this work is the analysis of interaction of elastic waves with the rough interface between two different solids. The presence of toughness leads to a significant increase in the resistance to heat transfer in nanostructures. This fundamental problem is discussed in relation to the commonly used method of wave scattering at rough surface: the Kirchhoff tangent plane method. The method assumes that at the point of the rough surface profile, the surface is regarded as locally smooth, and the reflection and transmission of the incident wave can be described by the scattering at the tangent plane of this point. Based on the elastic wave theory, we use the frequency-dependent continuity conditions to calculate the energy transmission coefficient at the interface. And then its effective value at the rough interface is estimated by using the Kirchhoff method. By substituting this effective value into the formula of Kapitza conductance, we can calculate the Kapitza conductance at the rough interface and analyze the effect of roughness on the interfacial heat transfer.
Statistical model of phonon scattering on rough boundaries of nanostructures
Authors: Barinov A A , Khvesyuk V I
Published: November 2021

Because of the rapid development of semiconductor electronics and the tendency to size reduction of the elements of transistors, there is an urgent task of assessing the heat transfer regime, which determines the ability to maintain the required thermal regime. In this work, the heat transfer in micro- and nanostructures in silicon is considered, and a comprehensive analysis of factors determining the heat transfer regime is carried out. In particular, the effect of the interaction of phonons with the sample boundaries in the quasi-ballistic and ballistic heat transfer regimes, where these processes play a decisive role, is evaluated using statistical model of phonon scattering on rough boundaries of samples.
Method for constructing the fundamental equation of state that takes into account the peculiarities of the substance behaviour in a wide vicinity of the critical point
Authors: Rykov S V , Kudryavtseva I V
Published: November 2021

On the basis of the phenomenological theory of the critical point and the Benedek hypothesis, an expression for the Helmholtz free energy F with scale functions in the density-temperature variables has been developed. The proposed free energy equation has been tested on the example of constructing the fundamental equation of state of 2,3,3,3-tetrafluoropropene (R1234yf). By comparison with the known experimental data on the equilibrium properties of R1234yf – density and pressure on the phase equilibrium line, p-ρ-T-data in the single-phase region, the second and third virial coefficients, isochoric heat capacity, isobaric heat capacity and the sound velocity – the operating range of the equation of state of R1234yf has been established according to temperature from 220 K to 420 K and pressure up to 20 MPa.