bluuebunny/crossref_metadata_2025_split huggingface dataset:
Symmetry breaking in annular jets with different blockage ratio
Authors: Ryzhenkov V O , Mullyadzhanov R I 
Published: December 2020

Abstract
We perform direct numerical simulations of the annular laminar jet flows for two inner-to-outer diameter (blockage) ratios br = d / D = 0.5, 0.9 in the range of the Reynolds number based on the bulk velocity inside the nozzle and its outer diameter Re = 200 – 400. In spite of the axisymmetric formulation, asymmetric states are observed for moderate and high Re. A gradual increase of the Reynolds number allow building a regime map. The symmetry-asymmetry transition Reynolds number decreases with the increase of br, while the steady-unsteady transition Reynolds numbers are close for both br. The degree of asymmetry increases with the increase of Re, leading to a shift of the global stagnation point from the axis of symmetry.
Experimental study of a turbulent structure in coplanar channels
Authors: Terekhov V I , Zolotukhin A V , Chohar I A 
Published: December 2020

Abstract
The experimental results of a three-dimensional turbulent flow structure inside the cells of flat coplanar channels with mutually intersecting edges on opposite walls are presented. In the experiments, a two-component laser Doppler speed meter is used, which allows measuring the averaged and pulsating velocity components. It is shown that a flow structure varies depending on a place of measurements inside a coplanar channels cell.
Evolution of mass flow and total temperature pulsations in flat-plate and swept-wing boundary layers at Mach 2 and 2.5
Authors: Yatskikh A A , Kosinov A D , Semionov N V , Ermolaev Y G , Panina A V , Kocharin V L , Afanasev L V 
Published: December 2020

Abstract
The experimental data on the development of natural disturbances during the laminar-turbulent transition in the boundary layers of a flat plate and a swept wing with a supersonic leading edge at Mach 2 and 2.5 are analyzed. Data are obtained using a hot-wire anemometer in the automatic scanning mode for overheating of the probe. The levels of pulsations of mass flow and disturbances of total temperature are determined using the modified diagrammatic method of Kovasznay taking into account the coefficient of correlation. It was found that at all stages of the laminar-turbulent transition of the flow in the boundary layer, the ratio of the levels of pulsations of the total temperature and pulsations of the mass flow and the correlation coefficient remain almost constant.
IR diagnostics of a flame of a new burner when burning liquid hydrocarbons in a steam jet
Authors: Anufriev I S , Kopyev E. P. , Loboda E. L. , Agafontsev M. V. , Mukhina M. A. , Sadkin I. S. 
Published: December 2020

Abstract
In the present work, we performed IR diagnostics in the external flame of a new burner using the example of waste engine oil being sprayed by a high-speed jet of superheated steam. The experiments were carried out in a wide range of operating parameters (steam flow rate and temperature and fuel flow rate). In measurements, we used a FLIR thermal imaging camera of the special JADE J530SB series and platinum-rhodium-platinum-rhodium thermocouple of type B. Instantaneous and average temperature fields are obtained. The influence of device operation parameters on the temperature in the external flame of the burner is established. The maximum temperature reaches 1240°C. With increasing mass concentration of steam, a decrease in temperature is observed. This is due to dilution of a combustible mixture and a decrease in its heat capacity. A decrease in the flame temperature in the presence of steam may indicate a decrease in formation of thermal nitrogen oxides.
Thermal decomposition of polyethylene agglomerates in a porous medium
Authors: Donskoy I G , Svishchev D A , Kozlov A N , Penzik M V 
Published: December 2020

Abstract
Fixed-bed combustion of compositions with polymeric materials (for example, municipal solid waste) is often difficult due to the agglomeration phenomenon: when heated, the waste particles swell and emit a significant amount of viscous products, resulting in formation of clumps of particles that have low air permeability. Using experimental and theoretical models, some features of the formation and decomposition of agglomerates are investigated. Samples of the agglomerates were prepared in a laboratory batch unit by heating a mixture of polyethylene granules and clay particles. Using a mathematical model, numerical calculations of the heating regimes were performed under the conditions of an experimental unit. A change in the shape of the agglomerate at different points in time is considered.
Changes in thermal conductivity of wood during its thermochemical conversion
Authors: Donskoy I G , Svishchev D A , Shamanskiy V A 
Published: December 2020

Abstract
Plant biomass is a fuel with better environmental characteristics than fossil fuels. The paper considers the effect of wood fuel conversion on its thermophysical properties. The measurements made allow us to establish a relationship between the degree of conversion and the coefficient of thermal conductivity. Thermal conductivity increases linearly with increasing density of samples and decreases as the pyrolysis proceeds, which is associated with a change in the porous structure and chemical composition of the material. The data obtained are used in a mathematical model of the pyrolysis of a wood particle. The influence of the anisotropy of the thermal conductivity coefficient on the characteristic drying and pyrolysis times is estimated.
Influence of the relative momentum flux ratio on the mixing of hydrogen jets in an M=4 crossflow
Authors: Fedorova N N , Goldfeld M A , Valger S A 
Published: December 2020

Abstract
The paper presents the results of numerical simulation of the 3D flows in a plane channel with the abrupt expansion. Sonic hydrogen jets are supplied from two circle orifices located opposite each other on the channel walls before the backward-facing step. The numerical simulations are carried out under the conditions of experiments performed at the hot-shot wind tunnel IT-302M ITAM SB RAS for the following flow parameters: Mach number at the entrance of the channel M = 3.84, the total temperature T0 = 1715 K, and the total pressure P0 = 6.5 MPa. Calculations were performed with a change in the jet supply pressure from 0.4 to 3.6 MPa, which ensures the variation in the jet-to-crossflow momentum flux ratio in the range of J = 0.7 ÷ 6. Mathematical modeling was performed in ANSYS Fluent based on the Reynolds-Averaged Navier-Stokes equations supplemented by the k-ω SST turbulence model. A comparison of the calculated and experimental data on the flow structure, as well as the static pressure distributions on the walls, indicates a satisfactory agreement. The calculated results made it possible to obtain a clearer understanding of the 3D flow structure in the channel and reveal the influence of the injection pressure on the level of mixing.
Heterogeneous and platinum-initiated homogeneous combustion of nitrogen-containing heterocyclic compounds in the argon and water vapor media at elevated pressure
Authors: Fedyaeva O N , Artamonov D O , Vostrikov A A 
Published: December 2020

Abstract
The paper presents the results on the oxidation of pyrrole and pyridine in the argon and water vapor media at high pressure and uniform heating of the tubular stainless steel reactor to 823 K. Experiments were carried out with lean and stoichiometric mixtures (fuel equivalence ratio φ = 0.78–1.01) at their dilution level x
D = 36–65% mol. Based on the time dependences of the reaction mixture temperature, it is revealed that oxidation proceeds via the mechanisms of homogeneous and heterogeneous reactions. It was found that the oxidation rate of pyrrole depends on the amount of corrosion products accumulated on the reactor wall. It is shown that a Pt-Rh/Pt thermocouple inserted into the center of the reaction volume intensifies pyridine oxidation in the near-surface region. The difference in the oxidation mechanisms of pyrrole and pyridine is explained by the structure of their molecules.
Superstructures in a diffusion torch
Authors: Lemanov V V , Lukashov V V , Sharov K A 
Published: December 2020

Abstract
The paper presents the experimental results for isothermal flows (CO2, propane) and diffusion flames (C3H8 or H2 mixed with CO2). Optical method of PIV (Particle Image Velocimetry) and flow visualization are used. The paper considers the features of the effect of vortex superstructures on an attached diffusion plume. When superstructures interact with the flame front, the question of choosing the determining scales becomes ambiguous. Apparently, the features of the perturbation interaction can depend on the acoustic characteristics of the flows and, accordingly, on the nature of the density distribution in the plume.
Three-dimensional modeling of gas injection into a closed liquid-filled tube region
Authors: Alekseev M V , Vozhakov V S , Lezhnin S I , Pribaturin N A 
Published: December 2020

Abstract
Three-dimensional modeling of air injection into a closed pipe region filled with liquid (water, liquid lead) is carried out at high pressure drops. It is shown that in the three-dimensional calculation, the instability of the interphase surface in the form of ring waves of deformation on the upper surface of the projectile is significantly manifested. When air is injected into water, the difference in the configuration of the interphase surface obtained in axisymmetric (two-dimensional) and three-dimensional calculations is insignificant. When injected into a liquid with a substantially higher density (liquid lead), this difference is especially pronounced in the compression phase of the gas projectile.
Reflection of a shock wave from a finely dispersed medium of low concentrations
Authors: Bashirova K I , Mikhaylenko C I 
Published: December 2020

Abstract
A model of a shock tube is prepared to study the behaviour of a shock wave in a layer of light elastic granular particles. Computational experiments are made using the OpenFOAM package. The prepared model allows carrying out simulations for pressure between 105 and 104 Pa and concentration of particles of 20%. Results are obtained on pressures in different time moments, depending on different densities of granular particles. An increase of the density of the granular particles is shown to decrease the blurring of the boundary between the media. It is also noted that a decrease in the density leads to double pressure peaks.
Modeling bubble distribution and heat transfer in polydispersed gas-liquid flow in a backward-facing step
Authors: Bogatko T V , Pakhomov M A 
Published: December 2020

Abstract
The numerical results on the flow, bubble distributions and heat transfer in a bubbly polydispersed flow in a horizontal duct with a backward-facing step are presented. The numerical model uses the Eulerian approach taking into account the back effects of bubbles on the mean and turbulent characteristics of the carrier fluid phase. The model takes into account the interphase momentum transfer, bubble break-up and coalescence processes. The set of 2D RANS equations is used for modeling two-phase bubbly flows. Turbulence of the carrier fluid phase is predicted using the second moment closure. The method of δ-function approximation is employed for simulation of gas bubble break-up and coalescence. The effect of the gas volumetric flow rate ratios on the flow structure and heat transfer in the two-phase flow is numerically studied. An increase in the gas volumetric flow rate ratios leads to a significant increase in the wall friction coefficient (almost 1.5 times in comparison with the single-phase flow regime). The addition of air bubbles results in a significant increase in the heat transfer rate (up to 50%).
Research of heat and mass transfer parameters at drying poly (ethylene terephthalate) granules
Authors: Geller Yu A , Antanenkova I S , Shatskikh Yu V 
Published: December 2020

Abstract
In this article, drying characteristics were studied for polyethylene terephthalate (PET) granules. For data analysis, a modified quasistationary method was used. The values of the reduced time and the hydrodynamic intensity index were obtained for the generalized drying curve of the entire drying process in the temperature range from 120 to 185°C. The duration of the first drying period of PET granules was determined for all experiments.
Application of the PTV with the use of a light-field camera to study three-dimensional wave regimes of liquid film flow
Authors: Kvon A Z , Bobylev A V , Guzanov V V , Kharlamov S M 
Published: December 2020

Abstract
We present the results of studying the influence of surfactants on three-dimensional waves, in particular, on the flow structures in the wave. Volumetric fluid velocity measurements in waves, as well as the determination of their shape, were carried out using a light field camera. An aqueous solution of the nonionic surfactant Triton-X was used as a working fluid. The presence of surfactant leads to a significant change in the structure of the transverse flow regions under the main hump of the wave. Besides, capillary precursor and backflow in it are suppressed.
Reflection of sound pulses from the boundary of the bubble medium
Authors: Ogorodnikov I A 
Published: December 2020

Abstract
The reflection of sound and radiation of a bubble medium under excitation by a short sound wave are studied for different values of the volume concentration of bubbles. It is shown that at the beginning of the interaction of the wave with the medium, reflection occurs as from a structureless soft boundary, which at the end of the interaction is replaced by radiation from an excited medium. The dependences of the reflection coefficient are obtained and the spectral characteristics of the radiation of the bubble medium are determined at the initial stage of the process and at large times when the radiation is steady-state. It is shown that the emission spectrum of the layer is continuous with a maximum in the frequency range of volume pulsations of free bubbles.
Jump of azimuthal velocity in a creeping two-fluid swirling flow
Authors: Sharifullin B R , Naumov I V , Kravtsova A Yu , Shtern V N 
Published: December 2020

Abstract
This work reveals a jump of azimuthal velocity at the interface that can be important for vortex bioreactors. The rotating lid controls the flow of two fluids in a vertical cylindrical container, the other walls of which are stationary. Near the lid, a centrifugal force pushes the upper fluid toward the sidewall, thereby developing its centrifugal meridional circulation. This motion drives the bulk counter-circulation in the lower fluid at a slow rotation. The use of sunflower oil for the upper fluid, alcohol-glycerine solutions for the lower fluid and the assembly of averaged PIV images allow measuring velocity and visualizing pattern even in a creeping motion. This advanced experimental method helps to detect velocity jumps occurring at the interface.
Computational study of cutting transport by drilling fluids in directional wells
Authors: Zhigarev V A , Pryazhnikov M I , Matveev A V , Mikhienkova E I , Guzei D V 
Published: December 2020

Abstract
The paper presents the computation results of the cutting transport in directional wells. Two samples of oil-based muds were prepared. The rheological parameters, incorporated in the computation model, were measured. The geometry of the real well was used for the computation. Three well slopes equal to 15, 45, 75 degrees were studied. The sludge velocity profiles in the annular channels were obtained. The average volumetric value of the particle slip velocity was obtained (the difference between the drilling fluid velocity and the sludge velocity).
Shape control of the crystal-melt interface in the Bridgman method
Authors: Kislitsyn S A , Berdnikov V S , Mitin K A 
Published: December 2020

Abstract
The processes of silicon crystallization in flat-bottomed cylindrical graphite crucibles in the modes of conjugate convective heat transfer with allowance for latent heat are numerically investigated. The influence of hydrodynamics and heat transfer on the local shape of the crystal-melt interface has been studied. The hydrodynamics of a silicon melt is investigated in the modes of thermogravitational and thermal gravitational-centrifugal convection. First, the effect of the velocity of lowering the crucible into the cold zone was studied. Then, at the set crucible lowering velocity, the influence of the crucible angular velocity was studied. The problems were solved in a nonstationary formulation by the finite element method.
Study of the effect of three-dimensional capillary-porous coatings with various microstructural parameters on heat transfer and critical heat flux at pool boiling of nitrogen
Authors: Kuznetsov D V , Pavlenko A N , Chernyavskiy A N , Radyuk A A 
Published: December 2020

Abstract
An experimental study of the effect of capillary-porous coatings obtained by directional plasma spraying on heat transfer and critical heat fluxes during pool boiling of nitrogen under conditions of stationary heat release on copper tubular heaters with a diameter of 16 mm was carried out. It is shown that for the coating with the highest porosity, the maximum increase in the critical heat flux is 1.8 times higher than that for a smooth heater. The maximum heat transfer coefficients were observed on TCP coatings in the region of low heat fluxes, which were up to 3.5 times higher than the heat transfer coefficients on a smooth heater. The effect of the thickness of the residual layer of microstructured capillary-porous coatings on heat transfer during nucleate boiling is shown. Based on the data of high-speed video recording, it was shown that the intensification of heat transfer during boiling on structured capillary-porous surfaces is not associated with an increase in the nucleation site density. Revealed pulsating nature of boiling in the region of high heat fluxes is characterized by the periodic formation and departure of vapor conglomerates along the surface of the heater.
Condensation growth of microdroplets levitating over a heated liquid film
Authors: Shatekova A I 
Published: December 2020

Abstract
This work is devoted to the study of such an interesting phenomenon as levitation of liquid microdroplets above the surface of a heated film. Levitating microdroplets of liquid are formed due to condensation of the upward flow of steam. The height of the drop levitation is comparable to their size. This paper presents new experimental data on the dependence of the droplet diameter on time. Microdroplets of liquid being in a two-dimensional array of microdroplets and levitating above the heated liquid film constantly grow due to condensation. The diameter of the droplets practically linearly increases with time. The obtained non-trivial results require further careful research.
Intensification of heat transfer in falling films on a bundle of horizontal tubes with microstructured surface
Authors: Volodin O A , Pecherkin N I , Pavlenko A N , Zubkov N N , Kataev A I , Mironova I B , Das M K 
Published: December 2020

Abstract
Experimental results on measuring heat transfer in falling films of R21 refrigerant on a bundle of horizontal tubes with structured surfaces are presented. The experiments were carried out in the range of Reynolds number of the saturated liquid film from 500 to 1500 at a pressure of 3 bar in the evaporator. To intensify heat transfer, copper tubes with an external surface treated by the method of deformational cutting (MDC) were used. Three types of structures were used: structure No. 1 with half-closed microcavities, structure No. 2 with a rhomboid shape, and structure No. 3 created on the basis of structure No. 2 with additional transverse ribbing. It was shown that the studied types of structures can significantly increase the heat transfer coefficient as compared to a smooth surface. The structure with half-closed microcavities was the most effective for heat transfer enhancement.
Mathematical model for predicting the formation of ferrous deposits during coal combustion
Authors: Chernetskiy M. Yu. , Butakov E. B. 
Published: December 2020

Abstract
For the first time, on the basis of a combined model of the principal component method and neural network modeling method, a unified method for evaluating coals for the formation of strong ferrous deposits is proposed, taking into account the ash composition, combustion conditions and the degree of grinding. The results of predicting the propensity to form ferrous deposits of Rfe have shown acceptable accuracy of determination. Expanding the experimental database on different types of coals will improve the accuracy of modeling and the widespread use of this technique in the energy sector.
Laboratory setup for microwave drying of brown moisture carbon
Authors: Karelin V A , Salomatov Vl V 
Published: December 2020

Abstract
A setup has been created to study the drying of wet coals by microwave radiation with a frequency of 2.45 GHz. Time dependences of humidity and surface temperature of brown coal samples from the Talovskoye deposit in Siberia are measured at an absorbed energy density of about 30 W g−1. The analysis of the data obtained is carried out and the mechanisms of possible processes that explain the observed patterns are considered.
Experimental study of heat transfer processes during the operation of WWER steam generator in emergency mode on a single-tube model
Authors: Shlepkin A S , Morozov A V , Sakhipgareev A R 
Published: December 2020

Abstract
The paper presents the results of experimental research of the heat transfer processes during the operation of a WWER steam generator in emergency condensation mode. The experiments are carried out at a research facility with a test section in the form of a single-tube model of a steam generator. The geometric characteristics of the tube and the main research parameters, such as temperature and pressure, are similar to the real steam generator. Several stages of research are planned: with pure water steam, with a fixed concentration of boiling boric acid and with a variable concentration of acid in the solution. The results of the first series of experiments performed on pure water steam are presented. As a result of research, the heat flux density is determined, and the values of the heat transfer coefficient during steam condensation in a single horizontal tube are calculated.
Equation of state of hard-sphere fluid in nanoporous media
Authors: Andryushchenko V A , Boyko E V 
Published: December 2020

Abstract
The present work is devoted to the study of fluid equations of state in nanoporous media. The modelling is carried out in the framework of the molecular dynamics method using the potential of hard spheres. The dependences of the compressibility factor on packing fraction are studied for various characteristic pore sizes, porosities, and types of grains packing of a porous medium. It is shown that for all cases considered, deviations of the obtained equations of state from the Carnahan-Starling equation of state are insignificant. These deviations may be due to the presence of restricted zones in a porous medium inaccessible to fluid molecules that is also discussed in the work.