bluuebunny/crossref_metadata_2025 huggingface dataset:
An approximately analytical solution method for the cable-driven parallel robot in FAST
Authors: Yin Jia-Ning , Jiang Peng , Yao Rui
Published: March 2021

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the largest single-dish aperture telescope with a cable-driven parallel robot introduced to achieve the highest sensitivity in the world. However, to realize the high-precision, mechanical equations of such a robot are always complicated, so that it is difficult to achieve real-time control by the traditional iterative method. In this regard, this paper proposes an approximately analytical solution method, which uses the approximately linear relationship between the main parameters of FAST to bypass some iterations. With the coefficients of the relationship extracted, static or quasi-static mechanical equations can be analytically solved. In this paper’s example, this method saves at least 90% of the calculating time and the calculated values are consistent with the experimental data. With such huge efficiency improvements, real-time and high-precision control of the FAST will no longer be difficult work. Besides, all the work in this paper is expected to be used in the FAST.
Algorithm for extracting intersections in PPV space of filaments
Authors: Zhang Chao , Ren Zhi-Yuan , Wang Chen , Wu Jing-Wen , Ma Xiao-Yun
Published: March 2021

A filament is an important structure for studying star formation, especially intersections of filaments which are believed to be more dense than other regions. Identifying filament intersections is the first step in studying them. Current methods can only extract two-dimensional intersections without considering the velocity dimension. In this paper, we propose a method to identify three-dimensional (3D) intersections by combining Harris Corner Detection and Hough Line Transform, which achieve a precision of 98%. We apply this method for extracting intersection structures of the OMC-2/3 molecular cloud and to study its physical properties and obtain the associated PDF distribution. Results show denser gas is concentrated in those 3D intersections.
Low-dimensional materials for photovoltaic application
Authors: Kondrotas Rokas , Chen Chao , Liu XinXing , Yang Bo , Tang Jiang
Published: March 2021

The photovoltaic (PV) market is currently dominated by silicon based solar cells. However technological diversification is essential to promote competition, which is the driving force for technological growth. Historically, the choice of PV materials has been limited to the three-dimensional (3D) compounds with a high crystal symmetry and direct band gap. However, to meet the strict demands for sustainable PV applications, material space has been expanded beyond 3D compounds. In this perspective we discuss the potential of low-dimensional materials (2D, 1D) for application in PVs. We present unique features of low-dimensional materials in context of their suitability in the solar cells. The band gap, absorption, carrier dynamics, mobility, defects, surface states and growth kinetics are discussed and compared to 3D counterparts, providing a comprehensive view of prospects of low-dimensional materials. Structural dimensionality leads to a highly anisotropic carrier transport, complex defect chemistry and peculiar growth dynamics. By providing fundamental insights into these challenges we aim to deepen the understanding of low-dimensional materials and expand the scope of their application. Finally, we discuss the current research status and development trend of solar cell devices made of low-dimensional materials.
Impact of brain shift on neural pathways in deep brain stimulation: a preliminary analysis via multi-physics finite element models
Authors: Luo Ma , Narasimhan Saramati , Larson Paul S , Martin Alastair J , Konrad Peter E , Miga Michael I
Published: March 2021

Objective. The effectiveness of deep brain stimulation (DBS) depends on electrode placement accuracy, which can be compromised by brain shift during surgery. While there have been efforts in assessing the impact of electrode misplacement due to brain shift using preop- and postop-imaging data, such analysis using preop- and intraop-imaging data via biophysical modeling has not been conducted. This work presents a preliminary study that applies a multi-physics analysis framework using finite element biomechanical and bioelectric models to examine the impact of realistic intraoperative shift on neural pathways determined by tractography. Approach. The study examined six patients who had undergone interventional magnetic resonance-guided DBS surgery. The modeling framework utilized a biomechanical approach to update preoperative MR to reflect shift-induced anatomical changes. Using this anatomically deformed image and its undeformed counterpart, bioelectric effects from shifting electrode leads could be simulated and neural activation differences were approximated. Specifically, for each configuration, volume of tissue activation was computed and subsequently used for tractography estimation. Total tract volume and overlapping volume with motor regions as well as connectivity profile were compared. In addition, volumetric overlap between different fiber bundles among configurations was computed and correlated to estimated shift. Main results. The study found deformation-induced differences in tract volume, motor region overlap, and connectivity behavior, suggesting the impact of shift. There is a strong correlation (R = −0.83) between shift from intended target and intended neural pathway recruitment, where at threshold of ∼2.94 mm, intended recruitment completely degrades. The determined threshold is consistent with and provides quantitative support to prior observations and literature that deviations of 2–3 mm are detrimental. Significance. The findings support and advance prior studies and understanding to illustrate the need to account for shift in DBS and the potentiality of computational modeling for estimating influence of shift on neural activation.
The role of edge plasma parameters in H-mode density limit on the JET-ILW
Authors: Sun H.J. , Goldston R.J. , Huber A. , Xu X.Q. , Flanagan J. , McDonald D.C. , de la Luna E. , Maslov M. , Harrison J.R. , Militello F. , Fessey J. , Cramp S.
Published: March 2021

A study of a dataset of JET H-mode plasma with the Be/W ITER-like wall (JET-ILW) shows that reaching the edge MHD ballooning limit leads to confinement degradation. However, unlike JET plasmas with a carbon wall (JET-C), the JET-ILW plasmas stay in a marginal dithering phase for a relatively long period, associated with a higher (≈20%) H-mode density limit (HDL) than JET-C equivalents. This suggests that ITER could be operated in H-mode with higher density than the scaling based on carbon wall devices, but likely with a dithering phase plasma with lower confinement. A new, reliable estimator for JET E
r, min has been derived by combining HRTS measurements of pedestal gradient and edge-SOL decay lengths. JET radial E
r ETB wells are observed in the range of −15 to −60 kV m−1 in high performance H-modes, consistent with previous CXRS results in ASDEX Upgrade. The results imply that a higher positive E × B shear in the near SOL plays a role in sustaining a marginal phase in JET-ILW which leads to a higher HDL than that in JET-C. The results of the JET-ILW dataset show agreement with the Goldston finite collisionality HD model for SOL broadening at high collisionality. A hypothesis for the dithering H-mode phase is proposed: as n
e,SOL increases, ν
∗,SOL increases, SOL broadens, E
r shear decreases, triggers L-mode; n
e drops, ν
∗,SOL decreases, SOL becomes narrower, and E
r shear increases, triggering H-mode, resulting in a cycle of H–L–H- oscillations. For burning plasma devices, such as ITER, operating just below the MHD limit for the dithering phase could be a promising regime for maximising core density, and fusion performance while minimising plasma-material interaction. The oscillatory signal during the dithering phase could be used as a precursor of undesirable plasma performance for control purposes.
Maximal relevance and optimal learning machines
Authors: Duranthon O , Marsili M , Xie R
Published: March 2021

We explore the hypothesis that learning machines extract representations of maximal relevance, where the relevance is defined as the entropy of the energy distribution of the internal representation. We show that the mutual information between the internal representation of a learning machine and the features that it extracts from the data is bounded from below by the relevance. This motivates our study of models with maximal relevance—that we call optimal learning machines—as candidates of maximally informative representations. We analyse how the maximisation of the relevance is constrained both by the architecture of the model used and by the available data, in practical cases. We find that sub-extensive features that do not affect the thermodynamics of the model, may affect significantly learning performance, and that criticality enhances learning performance, but the existence of a critical point is not a necessary condition. On specific learning tasks, we find that (i) the maximal values of the likelihood are achieved by models with maximal relevance, (ii) internal representations approach the maximal relevance that can be achieved in a finite dataset and (iii) learning is associated with a broadening of the spectrum of energy levels of the internal representation, in agreement with the maximum relevance hypothesis.
Molecular Dynamics Simulation of the Leidenfrost Effect
Authors: Biryukov D A , Gerasimov D N , Yurin E I
Published: March 2021

Results of the molecular dynamics simulation of the contact between an argon droplet and an overheated copper surface (with the temperature exceeding critical for argon) are presented. The direct contact of argon (supercritical fluid) and the overheated surface is observed in the numerical experiment. Dynamics of the droplet size change is described by a simple equation.
Experimental study of heat transfer, hydrodynamics and drying kinetics in a centrifugal fluidized bed apparatus
Authors: Nadeev A A , Barakov A V , Dubanin V Yu , Muravev A V , Khripunov K G , Solzhenikin P A
Published: March 2021

This paper presents the test results of a prototype installation for drying dispersed materials in a centrifugal fluidized bed. The prototype is a batch apparatus with a vertical supply of a drying agent. A diagram of a test bench designed to study the hydrodynamics of the apparatus and the heat and mass transfer process during drying in a centrifugal fluidized bed is given and described. Silica gel with a particle diameter of 3.8 mm was used as a dispersed material. Hydrodynamic experiments were carried out on a “cold” model. Based on their results, the relationship of the hydraulic resistance of the apparatus at various values of the air velocity and mass of material in the working chamber is constructed. Experimental data have been obtained on low-temperature drying of silica gel in a centrifugal fluidized bed for various modes. The data are presented as time relationships of the temperature and humidity of the material and the drying agent. Analysis of the data obtained showed that the heat and mass transfer process in a centrifugal fluidized bed has a high intensity. A positive conclusion is made about the possibility of using this apparatus for low-temperature drying of capillary-porous bodies.
An effective numerical method for simulating chemically and thermally nonequilibrium gas flows
Authors: Molchanov A M
Published: March 2021

A new efficient implicit numerical method has been developed for solving the equations of compressible viscous chemically and thermally nonequilibrium gas flow on structured grids. In this method, the problem of stiff is completely solved (the scheme is unconditionally stable), the number of matrix inversions is reduced, and the matrices themselves are factorized into smaller ones, and their inversion requires significantly less computer resources than for a fully implicit scheme. High convergence rate is achieved due to the fact that the algorithm can significantly reduce the decomposition errors of the approximate matrix in two ways. Test calculations were carried out, which showed a high efficiency of the proposed numerical schemes.
Fast decomposition on proper vectors in multidimensional space
Authors: Gerasimov D N , Morgunova S B
Published: March 2021

A recursive method to obtain proper vectors for a data set representation is proposed. This method faster than Karhunen-Loève expansion in SVD-realization for multidimensional space.
The Cavitation Process in Proximity to an Ultrasonic Waveguide
Authors: Biryukov D A , Gerasimov D N , Yurin E I
Published: March 2021

Ultrasonic cavitation may be accompanied by sonoluminescence – light emission from the cavitation area. The work discusses the connection between two-phase domains and light emission (sonoluminescence). Experimental evidences provide some proves to non-thermal theories of sonoluminescence.
Gradient heatmetry for boiling of underheated water on spherical surface
Authors: Sapoznikov S Z , Mityakov V Yu , Pavlov A V , Bobylev P G
Published: March 2021

The method of gradient heatmetry made it possible to obtain the distribution of local heat flux per unit area for boiling of subcooled water on the surface of the ball.
Heat transfer between human and fluid under extreme conditions of partial body cryotherapy
Authors: Kolishkin L M , Shakurov A V
Published: March 2021

This paper is aimed to study the cooling gas, cryocabin and skin temperature distributions to clear the partial body cryotherapy dosing. First, an experiment was performed in an empty cabin. It showed the effect of heat flow from the cabin walls to the cooling gas, as well as the distribution of gas temperature in the cabin without the human heat load. Second, an experiment was conducted with a volunteer. It showed the influence of the human heat load on the gas temperature, as well as the relationship between the skin surface temperature and the cooling gas temperature. Also, after the cooling gas supply is stopped, the dynamics of gas in the cabin, the cabin walls and the patient’s skin rewarming are considered. Data on the actual temperatures during cryotherapy may help correct current empiricism of cryotherapy protocols.
Cooling simulation of an aluminium ingot during heat treatment
Authors: Gorshenin A S , Krasnova N P , Rakhimova J I
Published: March 2021

This paper is devoted to the cooling process of aluminum ingots after heat treatment. The defects of semi-finished aluminum and methods for their elimination are considered. A mathematical model of cooling one aluminum ingot is presented..
Searching of the optimum tilt of the pipe at condensation by using gradient heatmetry
Authors: Sapozhnikov S Z , Mityakov V Yu , Mityakov A V , Babich A Yu , Zainullina E R , Pavlov A V
Published: March 2021

The aim of the study is to determine optimum tilt of the pipe at film condensation by using of gradient heatmetry. Dependence of heat flux per unit area on time and azimuthal angle are presented for vertical, horizontal and inclined pipe. Maximal heat transfer coefficients for experimental conditions are observed for the angle 20° from vertical. The gradient heatmetry gives high informational content, which opens up new possibilities for studies of heat transfer during condensation.
Comparative study of performance of heat exchangers used in hypersonic wind tunnels
Authors: Drozdov S M , Rtishcheva A S
Published: March 2021

During the modernization of the TsAGI hypersonic wind tunnel, which implied an increase in the limiting values of stagnation parameters, and, consequently, the heat load, the operation of the main air cooler structures was analyzed. Two qualitatively different options are considered: Option-1, in which the flow moves in a large number of longitudinal tubes placed in a common compartment with cooling water circulating in the intertube area, and Option-2, that is a bundle of tubes (tubes of circular or elliptical section were considered) containing a moving cooler (water), and the air flow transversely moves in the intertube gaps. In the study, a previously worked out and experimentally verified approach to numerical simulation was implemented, according to which a through calculation of the flow and heat transfer was carried out in all areas of the duct with cooled walls (prechamber, nozzle, test section, diffuser) and a cooling compartment for the mode p
0=12 atm; T
0=5000 K; M≈7. The ANSYS FLUENT software package solved axisymmetric Navier-Stokes equations for viscous and heat-conducting gas using the Spalart-Allmaras turbulence model. For the flow in the area of the cooling compartment, the simplified Darcy’s model and the model of the “schematized axisymmetric tube bundle” were considered.
Features of vortex formation and heat transfer during cross flow around two cylinders
Authors: Guzeev A S , Sapozhnikov S Z , Mitiakov V Yu , Seroshtanov V V , Suchok V V , Vlasov A S , Zhidkov N A
Published: March 2021

The creation of all heat exchangers supposes the establishment of a quantitative and qualitative relationship between the flow and heat flux distribution at heat transfer surfaces. The paper presents the study’s results of the vortex flow’s structure and heat transfer near two circular cylinders. The distance between the cylinders ranged from 0.5d to 4d during the experiments (here d is the diameter of the cylinders). The vortex flow’s patterns in hydro- and wind tunnels in the Reynolds numbers’ range from 4000 to 40,000 are compared. To study heat transfer near the cylinders, gradient heat flux measurement was used. In aerodynamic experiments, both cylinders were heated with saturated steam, ensuring a constant surface temperature of the cylinder. The results showed an agreement of the flow patterns. The effect of distance and flow velocity on the flow around the second cylinder is revealed: there may be cases when the second cylinder is at rest, in other cases it fluctuates. Gradient heatmetry revealed a decrease in the level of fluctuations near the second cylinder. However, the average Nusselt number for the second cylinder is expectedly lower than for the first.
Efficiency of burning sediments of waste water in a boiling layer
Authors: Lyubov V K , Vladimirov A M , Koroleva P V
Published: March 2021

It has been experimentally shown that the Metso HYBEX steam boiler installed at CHP-1 of JSC APPM and designed to burn a mixture of bark and wood waste and sewage sludge ensures their efficient utilization without highlighting fuel oil. At boiler loads close to the nominal efficiency, the gross value was 85.22–85.24%. The environmental indicators of the boiler unit fully and even with a margin meet the requirements established by directive 2010/75 / EC and GOST R 50831-95. The operation of the boiler ensured the complete utilization of sewage sludge generated at the sewage treatment plant. The annual savings of fossil fuels amounted to more than 80 thousand tons of fuel equivalent. The total content of heavy metals in fly ash emitted into the atmospheric air by a recycling and energy boiler with a bubbling fluidized bed when burning high-moisture biofuels is many times lower than when burning coal, even in low-emission furnaces.
Simulation of the electrovortex flow in a linear approximation under the action of the external magnetic field
Authors: Georgievskaya E P , Mikhailov E A , Teplyakov I O
Published: March 2021

Electrovortex flows appear in a liquid metal when a non-uniform current interacts with its own magnetic field. They are very important in different electrometallurgical processes connected with melting of metals. We describe the electrovortex flow in a hemispherical container which is connected with experiment which is carried in Joint Institute of High Temperature. Our main aim is to study the influence of the extermal magnetic field, because the experiment shows that even weak Earth magnetic field can change the characteristics of the flow.

To solve this problem we formulate a system of equations using Stokes approximation. They are solved with Thoms’ boundary conditions using the time marching method. Our numerical scheme gives us the opportunity to parallelize the computing process. For the calculations we use the CUDA technology. It allows us accelerate the calculation process, even if we use low-power user graphics cards. We hope that our experience can be used to solved another similar problems.
Subcooled liquid boiling: details of the mechanism and phenomenological description
Authors: Vasil’ev N V , Khodakov K A
Published: March 2021

Using high-speed filming (with a frame frequency up to 100 kHz) the important details of the subcooled liquid boiling mechanism are specified, which allow to conclude that Snyder-Bergles phenomenological model describes the process with the maximal likelihood. This model accounts for the main subprocesses of the subcooled liquid boiling (evaporation of the liquid microlayer located under the bubble near the dry spot boundary, vapor condensation at the bubble dome, liquid inflow to the microlayer). It corresponds to the modern ideas regarding to boiling mechanism and qualitatively well meets the experimental data. On the basis of the conducted experiments the description of several subprocesses of the model is defined more exactly: nucleation sites deactivation, het removal from the bubble dome by means of unsteady heat conduction, bubble size evolution as a result from the balance of masses of the evaporating and condensing vapors. It was shown that large vapor agglomerates appear in the flow due to small vapor bubbles coalescence with a heat flux density increase. Formation of dry patches under the agglomerates was studied. These dry patches are precursors of the boiling crisis. Superheating of the surface under dry patches immediately leads to the heating surface burnout.
Heat transfer in cryosurgical device with an extended applicator
Authors: Pushkarev A V
Published: March 2021

This paper is aimed to study the prototype of cryosurgical device with an extended applicator. Three experiments were conducted. First, an experiment without heat load showed temperature distribution on extended applicator and its cooldown time. Second, an experiment with a typical heat load (when the applicator contacts the biotissue phantom) showed the impact of heat load on the surface temperature and on its cooldown time in this case, as well as the temperature at the control points inside the biotissue phantom and the dynamics of growth, shape and size of the freezing region. The third experiment was equivalent to the second, but without temperature sensors on the applicator surface for better freezing region visualization. Also, after the liquid nitrogen supply is stopped, the dynamics of thawing are considered. Data on the actual temperature during cryoexposure should help give basic recommendations for developing a cryoexposure technique with increased dosing accuracy.
Superheated metastable water atomization: fine atomized water plumes diagnostics and disperse characteristics; summary of results, applications in power generation and new techniques.
Authors: Zalkind V I , Zeigarnik Yu A , Nizovskiy V L , Nizovskiy L V , Schigel S S
Published: March 2021

Complex experimental investigation of superheated flow and dispersion characteristics of sprays in atomizing nozzles of various types is made. The comparative analysis of experimental and calculating investigations of thermo physic and hydro- gas-dynamic flow and disperse characteristics was carried out for various types of spray nozzles. It has shown that the main process, which determine peculiarities of superheated metastable water flow and phase transformation in spray nozzles, is quick (explosive) boiling up. And the optimal variant for superheated water atomization and achieving the most fine spray plumes, which contain mainly submicron droplet fraction, at initial temperature 240°C (and higher) is atomization by means of contracting-expanding nozzles. In such nozzles the explosive boiling is accomplished by quick transformation of foamed liquid into vapor-droplet flow. Diagnostic peculiarities are considered for these optically dense spray plumes; the auxiliary measurement methods were worked out for estimation superheated water high atomization level. The experimental and calculating data dimensionless treatment was made for achieving extremely fine (mainly submicron) superheated water spray. The dimensionless parameter, which determines necessary water (or some other liquids, for example – fuels) superheating level was derived. The possible technical applications of superheated water sprays are described, and up-to-date state of corresponding projects is given.
Simulation of the propagation of heat waves in a radiation-cooled dispersed stream of liquid droplet radiators
Authors: Safronov A A , Filatov N I , Grigoriev A L , Bondareva N V
Published: March 2021

The problem of radiation cooling of a moving dispers stream is solved taking into account the heat transfer along the movement of the stream due to the action of the radiation heat conduction mechanism. Taking this phenomenon into account leads to the formation of a heat wave region in the solution of model equations. The characteristic parameters of this heat wave are calculated, the influence of heat waves on the stability of the process of forming the equilibrium flow temperature profile is discussed.
Effect of interphase heat transfer on bulk condensation in dust-laden vapor-gas flow
Authors: Kortsenshteyn N M , Yastrebov A K
Published: March 2021

The model was proposed for homogeneous-heterogeneous bulk condensation in vapor-gas flow with dust particles. The feature of the model is taking into account temperature difference between gaseous phase and dust particles (with condensate on them). Calculations were carried out for mixture of D2O (vapor) and N2 (gas). The model was verified by comparison of results for the flow without dust with experimental data. Results were obtained for different values of mass fraction of dust, radius of dust particles and their initial subcooling. It was shown that there is minimal initial subcooling at which there is liquid on dust particles at nozzle outlet. This value depends on size of particles and mass fraction of dust.
Comparing the formation and propagation features of subcritical and supercritical thermal detonation waves
Authors: Melikhov V I , Melikhov O I , Saleh B , Shkel A A , Blinkov V N
Published: March 2021

During a severe accident in a nuclear reactor, an ex-vessel steam explosion may occur when the molten core come into contact with the liquid coolant, the crucial factor in the fuel-coolant interaction is the fragmentation of melt into small droplets, which rapidly increase the heat transfer to the coolant, and could lead to a steam explosion and formation of a pressure wave with a disastrous consequence for the surrounding components. In this research a numerical simulation of a steam explosion was performed using the VAPEX-D code which is being developed at the Department of NPP in “Moscow Power Engineering Institute” for the simulation of fuel-coolant interactions. Using the microinteractions concept, the propagation of thermal detonation waves was studied, and the characteristics of subcritical and supercritical waves were compared. A sharp increase in pressure is noted during the transition from subcritical mode to supercritical mode of propagation. A parametric study was performed where the volume fraction of corium was varied to determine the critical value at which the thermal detonation wave decayed. The study shows that increasing the melt volume fraction, will increase the maximum pressure and the velocity of the thermal detonation wave. While varying the initial void fraction showed that the thermal detonation wave can propagate in a very low melt volume fraction.
Investigation of the equalization capability of submerged perforated sheets forWWER-1500 horizontal steam generator
Authors: Le Thanh Tung , Melikhov V I , Melikhov O I , Nerovnov A A
Published: March 2021

Non-uniform heat transfer occurs at the steam generator secondary side, thus inducing a non-uniform steam generation and a non-uniform steam flow rate along the evaporation surface. In order to equalize the steam flow rate, submerged perforated sheet is installed in the horizontal SGs An analysis of the equalization of the non-uniform steam load in the WWER-1500 horizontal steam generator is performed using the STEG calculation code. Variant calculations of various options for the perforation of sheets allowed us to determine the design of submerged perforated sheet, which very well equalizes the initially non-uniform steam load.
The method of comparative analysis of the effectiveness of vapor-liquid compression cooling system and conventional liquid cooling system by relative energy indicators
Authors: Karelin D L , Boldyrev A V , Gureev V M , Boldyrev S V , Kharchyk S I
Published: March 2021

The article presents a new method for the comparative analysis of the effectiveness of a vapor-liquid compression cooling system and traditional solutions based on single-phase liquid and air cooling, while taking into account the combination of cooling capacity factors, the power expended on this, depending on the ambient temperature. As a result of numerical simulation, it was proved that the total power consumption CS

∑

N

c
s

′

for ensuring the operability of the vapor-liquid compression cooling system with increasing ambient temperature decreases relative to the similar total power consumption ∑N
CS for a system using traditional cooling methods. With increasing mass flow rate and temperature of the cooling air, the relative power consumption

∑

N

C
O

′

/

∑

N

C
O

for the functioning of the cooling systems under consideration becomes less than the relative energy indicator of the quantities of heat removed Q
И/Q
CO from the cooled object.
The active external heat and mass transfer multifunctional “one-wall” model with “nullified” friction resistance parietal boundary layer for the high-speed aircraft
Authors: Prudnikov A G , Mamaev V K , Zakharov N N , Severinova V V , Tarasenko A N
Published: March 2021

In this paper, a new “single-wall” scheme of a high-speed wingless jet aircraft without compressor, which has the smallest, practically “zeroed” external friction and heat and mass transfer resistance with an active external near-wall boundary layer and tangential injection of the superheated steam from a cooling jacket SCC walls was proposed. Moreover, due to the limited flow rate of the combustible laminar sublayer vapor injection and the laminar “scaly” sublayer zeroed friction, the average Mach number of the vortex external near-wall boundary layer will be only 2% less than the Mach number of the flight speed. This circumstance allows not to merge the frontier layer of the hull (“fuselage”), as is done on the overwhelming majority of the aircrafts, but to use the energy and mass of the near-wall boundary layer as a normal incoming air flow.
Direct numerical simulation of methane-air mixture combustion with extended kinetics at moderate Reynolds numbers
Authors: Semenev P A , Toktaliev P D
Published: March 2021

Results of direct numerical simulations of turbulent premixed combustion of methane-air mixture at model conditions in simple cubic computational domain at moderate Reynolds number Reλ∼50 and Karlovitz number Ka∼5 are presented. These conditions correspond to combustion regime with main oxidation reactions localized in thin area. Extended kinetic mechanism of methane oxidation is used for chemical reactions description. Laminar flame velocity values are obtained and compared with other results of 1D and 3D calculations. Thickness, form and local flame front structures are revealed based on computation results.
Modeling of Thermal-Hydraulic Processes in the Marine Power Installation Elements
Authors: Mitrofanova O V , Bayramukov A S , Ivlev O A , Urtenov D S , Fedorinov A V
Published: March 2021

The results of the current study presented the hydrodynamics and heat transfer features occur in the pipe systems of the thermal-hydraulic various elements of the ship nuclear power installations. A comparative analysis of the turbulent models choice, their approbation on typical elements of the curved pipelines, and comparison of the calculation results with experimental data were fulfilled. The conditions of the swirl flow crisis were determined on base of obtained results of theoretical studies and comparison with experimental data. The mechanism of occurrence of acoustic oscillations generated by large-scale vortex structures and causes of cyclic thermal loads were identified. The fundamental nature of the research, the use of the thermodynamic approach and the conclusions of the stability theory made it possible to predict the results of numerical calculations.
Investigation of the effect of nanoparticle coatings on the transport properties of a thermostabilizer evaporator
Authors: Kuzma-Kichta Yu A , Ivanov N S , Lavrikov A V , Shtefanov Yu P , Prokopenko I F
Published: March 2021

In the work, porous coatings of alumina nanoparticles are investigated. The coatings were formed by various methods. The dependence of the lift height of the nanofluid on its volume was established. The properties of the coating are compared with and without microtrenches.
Modeling of radiate characteristics of dispersion phase combustion products of energy fuels
Authors: Moskalenko NI , Dodov I R , Khamidullina M S , Safiullina Ya S
Published: March 2021

The results of an experimental study of the optical characteristics and microstructure of the dispersed phase of the products of combustion of organic fuel in oxygen and atmospheric air are analyzed. For gaseous fuels CmHn, the concentration of soot sol increases with an increase in the ratio of elements Cm / Hn. The microstructure of soot sol strongly depends on the residence time of the combustion products in the flame zone (chemical reaction zone) and the thermodynamic temperature. The maximum ash content is observed at thermodynamic temperatures of 1500-1800K zone of chemical reactions. The minimum ash content is observed when burning fossil fuels in oxygen with a value of the coefficient of excess oxygen α = 1,03. A technique is proposed for measuring the microstructure of soot sol in atmospheric emissions of the combustion products of turbojet engines, vehicles, and power plants. The results of studies of the microstructure of the dispersed phase of fuel combustion products are used to calculate the light scattering matrices of carbon black sol according to the Mi theory. The radiation characteristics of soot sols are simulated by their superposition for different fractions i of the sol microstructure with normalization to optical density |τi| and a wavelength of λ = 0.55mkm. The optical densities |τi| for λ=0,55mkm for components i are given in numerical form depending on the height z in the combustion chamber. The radiation characteristics (absorption, scattering cross section and scattering indicatrix) are presented in the spectral region of 0.2–40mkm in the form of an electronic computer database for various gamma distributions of the carbon structure of soot sol.
Experimental Research of Thermal Processes in Hydrogen-Oxygen Air Heater for Autonomous Power Supply System
Authors: Schastlivtsev A I , Borzenko V I , Shmatov D P
Published: March 2021

The results of experimental studies in hydrogen-oxygen air heater for autonomous power supply system are presented. As a result of studies, it was found that the use of a stepwise air supply scheme leads to the decrease in the formation of nitrogen oxides in a wide range of operation parameters. The separation of heating and air mixing into three zones ensured a decrease in the content of nitrogen oxides in the generated air down to 4 ppm. It was found that an increase in pressure in the combustion chamber leads to an increase in the completeness of hydrogen combustion and has practically no effect on the formation of nitrogen oxides. It is shown that nitrogen molecules directly enter the combustion zone with intensive oxidation, and to reduce the formation of nitrogen oxides, air must be supplied at a distance of at least 3 cooling zones in the combustion chamber.
The Use of Nanoparticles to Displace Oil from a Porous Medium
Authors: Pakharukov Yu V , Shabiev E K , Safargaliev R F , Simonov A S , Ezdin B S , Zarvin A E , Kalyada V V
Published: March 2021

The formation of supramolecular structures forming a transition region at the oil-nanofluid interface with a low surface tension is studied as a result of a synergistic effect in the interaction of planar graphene nanoparticles and silicon carbide nanoparticles coated with graphene layers (Core-shell). In model experiments on a Hele-Shaw cell, it was shown that in a porous medium such hybrid nanofluids have a high displacing ability of residual oil. At the same time, the oil – nanofluid interface remains stable, without the formation of sticky fingers. In the process of research using power electron microscopy, a transition region was observed, in the structuring of which nanoparticles were directly involved. The efficiency of displacement by hybrid nanofluid depends on the concentration of nanoparticles and their interaction.
Study of radiation heat transfer during combustion of liquid fuel in a rectangular channel
Authors: Abdurakipov S , Zamashchikov A , Chesnokov E , Ronshin F , Semionov V , Vladimirov V , Dementiev Y
Published: March 2021

An experimental study of radiation heat transfer during combustion of a flammable liquid in a narrow rectangular channel is performed. The emission spectrum of combustion products and the absorption spectrum of butanol-1 are obtained. The case when the temperature of the combustible liquid is lower than the flash point is investigated. A comparative analysis of emission and absorption spectra shows that they do not intersect well, and the radiative heating of the liquid during diffusion flame propagation along the surface cannot be too large.
Heat transfer on a capillary-porous surface during evaporation / boiling of a thin layer of liquid at low pressures
Authors: Zhukov V I , Brester A E , Pavlenko A N , Butko A S , Shvetsov D A
Published: March 2021

This paper presents experimental data on heat transfer during the evaporation/boiling of n-dodecane on a surface with a capillary-porous coating in a wide pressure range. The obtained data are compared with data on heat transfer during the evaporation/boiling of n-dodecane on a smooth surface. It was found that the regime of bubble boiling occurs on a coated surface at lower pressures than on a smooth surface. It was found that enhanced heat transfer during evaporation/boiling on a capillary-porous surface as compared with a smooth surface is observed only under conditions of bubble boiling (P ≥ 103 Pa).
Heat transfer crisis investigation in a microchannel with and without nanoparticles coating
Authors: Kuzma-Kichta Yu A , Lavrikov A V , Shustov M , Kustova E A , Ivanov N S , Kuleshov E A , Kiselev A S
Published: March 2021

Heat transfer crisis was investigated during water boiling in a microchannel without coating and with coating of aluminum oxide nanoparticles. Experiments were performed on an advanced setup with a horizontally located microchannel with dimensions of 12.5x3x0.2 mm. Calculation of the critical heat flux in the microchannel without coating and with a coating from nanoparticles, carried out by formulas for heat transfer crisis in a horizontal pipe with microporous coating and one-sided heating. For the microchannel coated with nanoparticles the critical heat flux was calculated for the conditions of no influence of liquid subcooling and initial section. The satisfactory agreement between the experimental and calculated data was obtained. dependences of the critical heat flux from the coating thickness and characteristic size of particles were also shown. However, the data array is limited and needs to be expanded what will improve the equations for critical heat flux in a microchannel with nanoparticles coating.
Experimental study of a flow structure in coplanar channels
Authors: Terekhov V I , Zolotukhin A V , Chohar I A
Published: March 2021

The results of an experimental three-dimensional flow structure study in flat coplanar channels with mutually intersecting ribs on opposite walls are presented. The measurements were carried out for different angle values between ribs (2β = 60°, 90°, 120°) and Reynolds number variations. In the experiments, a two-component laser Doppler speed meter was used, which makes it possible to measure both averaged and pulsating velocity components. It is shown that a flow structure in vortex cells between ribs varies greatly from a cell location and an angle between ribs. The magnitude of hydraulic losses in coplanar channels significantly exceeds losses in smooth channels, and they increase with increasing angle between ribs.
An experience in eddy resolving simulation of mixed convection in a rotating annular cavity with one heated disk and axial throughflow
Authors: Abramov A G , Zaitsev D K , Smirnov E M , Smirnovsky A A
Published: March 2021

Results of numerical simulation of the flow and heat transfer in a rotating annular cavity with one heated disk and axial throughflow are presented. To assess the model effect on the solution, various vortex-resolving techniques and different computational grids have been applied. The simulation results are compared with experimental data available. Consistent with the measurements, the numerical flow analysis has revealed the presence of two pairs of cyclonic and anti-cyclonic global circulations. It has been found that all computational models tested underestimate considerably both the mean heat flux and the mean rotational velocity lag whereas the results obtained using different models are relatively close to each other.
Cross verification of a simplified model of pure steam condensation in a tube bundle using experimental and CFD-simulation data
Authors: Gubarevich T A , Klementiev A A , Minko K B , Yankov G G
Published: March 2021

This paper presents an analysis of a simplified model of pure steam condensation in a bundle of smooth horizontal tubes. The model was based on classical recommendations for calculating the condensation process in tube bundles. Two different approaches were used to calculate the condensation heat transfer coefficient in the model. First, the inundation effect was not considered, and the average heat transfer coefficient was calculated for condensation on a single cylinder using the Nusselt equation. Second, condensation drainage which is asymmetric to the vertical diameter of the tube was considered. The results of these calculations were verified using available experimental data. The analysis of distributions of condensation local characteristics was presented. The results of detailed CFD simulation using a previously developed author’s model was employed for additional cross-verification of closing equations used in the simplified model.
Subcooled pool film boiling heat transfer from sphere: experiment and modelling
Authors: Duplyankin R A , Glazkov V V , Ivochkin Y P , Kubrikov K G , Sinkevich O A
Published: March 2021

Experiments were conducted to study heat and mass transfer at film boiling on a metal sphere immersed into subcooled liquid. A model was elaborated to calculate the thickness of the vapor film and the speed of vapor flow in the film. The model also includes a detachment model for vapor bubbles lifting off the surface of the film. The model shows agreement with the results of the pool film boiling experiments with various liquids as well as for Leidenfrost drops. Quite reasonable agreement is also observed for the frequency of bubble detachment in saturated liquid. While processing the experimental data the calculations showed that the heat transfer into the bulk of liquid from vapor-liquid boundary is much more intense than expected. The effect is not determined solely by natural convection within the liquid as the heat flows determined by natural convection are two orders of magnitude less than those obtained. An attempt was made to determine the consequent heat transfer coefficient based upon experimental data for the frequency of bubble detachment from off the vapor film around the sphere. The abnormally high heat transfer detected could be important in practical applications.
Numerical solution of the conjugate heat transfer problem for turbulent liquid flow in a tube using the large eddy simulation method
Authors: Artemov V I , Makarov M V , Yankov G G , Minko K B
Published: March 2021

This article presents the results of turbulent flow and temperature fluctuations simulation in the liquid and the tube wall in a conjugate formulation using the hybrid Reynolds-averaged Navier-Stokes / large eddy simulation (RANS/LES) method. Calculations are performed for water, air and mercury. The results show that the “conjugate” LES model implemented in in-house CFD code ANES provides a good reproduction of the available experimental results on temperature fluctuations near the wall for cases of different wall thicknesses and thermal activity of the wall material and the fluid. An approximate model for the wall is proposed and can be used as a boundary condition for calculations by direct numerical simulation (DNS) and LES methods in the non-conjugate formulations.
Calculation of critical heat fluxes at boiling on microstructured surfaces
Authors: Stupakova AV , Dedov AV
Published: March 2021

A method for increasing the critical heat flux at boiling by applying porous structures of various regular geometries to a smooth surface is considered. The analysis of experimental data and calculation of the critical heat flux based on the model of V.V. Yagov, which considers the additional inflow of liquid into the evaporation zone due to the action of capillary forces in a porous space. Comparison of experimental and calculated data allows us to conclude that this model is not suitable for all microstructured surfaces.
Investigation of heat transfer during cooling of a high-temperature target by a dispersed coolant flow
Authors: Komov A T , Sherbakov P P , Zakharenkov A V , Smorchkova Yu V , Ilyin V V , Shteling V S , Sherbakov S P
Published: March 2021

An experimental study of the heat flux density and the heat transfer coefficient during cooling of a high-temperature surface by a dispersed liquid flow has been carried out. The results of an experimental study on the possibility of removal heat fluxes of high density and thermal stabilization of an energy-loaded surface are obtained. Experimental data were obtained with stationary heat transfer in the following range of operating parameters of the coolant: water pressure 0.2 ÷ 0.4 MPa, mass flow rate of water 0.0033 ÷ 0.015 kg / s; induction heating power 7 ÷ 20 kW.
Some results of the study of heat transfer during the cooling of the high-temperature surface of the working section by the dispersed flow of the coolant
Authors: Demidov A S , Tupotilov I A , Zakharenkov A V , Loktionov V D , Dedov A V
Published: March 2021

In this paper investigates the heat exchange of the high-temperature surface of the working area during cooling by a dispersed two-component flow. A brief description of the experimental stand, the working section of the spraying device for creating a dispersed flow is given. The results of experimental modeling of the cooling of the working section at different regime parameters of the flow and supplied electric powers are presented. Data on the distribution of the wall temperature along the length of the heated working section are obtained. The thermal flux density on the side surface of the working area was estimated based on the readings of thermocouples in the work area. The operating parameters of the coolant at which the sample is cooled most effectively are determined.