bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractFlow 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

AbstractThe 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.