bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic energy distribution for neutron-induced fission of neptunium isotopes
Authors: Kaldiani P Mehdipour
Published: December 2020

The mean total kinetic energy as a function of fission fragments, the  distribution, is presented for neutron-induced fission of

Np using the scission point model. The calculated results of  for neutron-induced fission of

Np are compared with the available experimental data to obtain the deformation parameters in the scission point model. The deformation parameters of fission fragments are discussed at the scission point. The calculated results are also compared with the results from other methods and with experimental data. The behavior of the  distribution is then studied for the neutron-induced fission of actinides. This indicates that the  values for neutron-induced fission of actinides with odd mass numbers are greater than for those with even mass numbers.
Thermodynamics and weak cosmic censorship conjecture in Born-Infeld-anti-de Sitter black holes *
Authors: Zeng Xiao-Xiong , Zhang Hai-Qing
Published: December 2020

In this study, we examine the laws of thermodynamics and the weak cosmic censorship conjecture in the normal and extended phase spaces of Born-Infeld-anti-de Sitter black holes by considering a charged particle absorption. In the normal phase space, the first and second laws of thermodynamics as well as the weak cosmic censorship are still valid. However, in the extended phase space, the second law of thermodynamics is violated for double-horizon black holes and part of single-horizon black holes. The first law of thermodynamics and the weak cosmic censorship conjecture are still valid for all types of black holes. In addition, we found that the shift of the metric function, which determines the locations of the horizons, takes the same form at the minimum point in both the normal and extended phase spaces, indicating that the weak cosmic censorship conjecture is independent of the thermodynamic phase space.
Turbulent transport driven by kinetic ballooning modes in the inner core of JET hybrid H-modes
Authors: Kumar N. , Camenen Y. , Benkadda S. , Bourdelle C. , Loarte A. , Polevoi A.R. , Widmer F. , contributors JET
Published: December 2020

Turbulent transport in the inner core of the high-β JET hybrid discharge 75225 is investigated extensively through linear and non-linear gyro-kinetic (GK) simulations using the GK code GKW in the local approximation limit. Compared to previous studies (Citrin et al 2015 Plasma Phys. Control. Fusion
57 014032; Garcia et al 2015 Nucl. Fusion
55 053007), the analysis has been extended towards the magnetic axis, ρ < 0.3, where the turbulence characteristics remain an open question. Understanding turbulent transport in this region is crucial to predict core profile peaking that in turn will impact the fusion reactions and the tungsten neoclassical transport, in present devices as well as in ITER. At ρ = 0.15, a linear stability analysis indicates that kinetic ballooning modes (KBMs) dominate, with an extended mode structure in ballooning space due to the low magnetic shear. The sensitivity of KBM stability to main plasma parameters is investigated. In the non-linear regime, the turbulence induced by these KBMs drives a significant ion and electron heat flux. Standard quasi-linear (QL) models are compared to the non-linear results. The standard reduced QL models work well for the E × B fluxes, but fail to capture magnetic flutter contribution to the electron heat flux induced by the non-linear excitation of low k

θ

ρ
i micro-tearing modes that are linearly stable. An extension of the QL models is proposed allowing better capturing the magnetic flutter flux.
Current profile and normalized beta control via feedback linearization and Lyapunov techniques
Authors: Pajares Andres , Schuster Eugenio
Published: December 2020

Simultaneous control of the current profile and normalized plasma beta is an essential control problem in the development of advanced tokamak scenarios. However, this control problem is especially challenging due to the nonlinear nature of the current, heat, and particle transport dynamics, as well as the difficulty to understand and accurately model such processes. In this work, a nonlinear, robust, model-based controller for the simultaneous regulation of the current profile and normalized beta has been designed using feedback linearization and Lyapunov redesign techniques. Feedback linearization avoids approximate linearization of the plasma dynamics, retaining the original physics content of the model. Moreover, the use of Lyapunov redesign techniques makes the controller robust against the uncertainties arising during the modeling process. The controller’s performance in the presence of unknown dynamics is tested in nonlinear, one-dimensional simulations using the Control Oriented Transport SIMulator (COTSIM) code, which employs plasma models that are significantly more complex than those employed for control synthesis.
On coherent structures and heat transfer in strongly swirling impinging jets
Authors: Abdurakipov S , Sharaborin D
Published: December 2020

This work is devoted to the experimental study of coherent structures in swirling jets flowing onto a heated surface. To measure the velocity fields with a high acquisition rate of 3.5 kHz Stereo Particle Image Velocimetry (PIV) measurement system is used. Simultaneously with PIV measurements, the temperature of the heated surface is measured by high-speed thermometry. The experiments are carried out for three different cases of swirling and two distances from the nozzle to the impingement surface. It is shown that only in the case of strongly swirling jet breakdown of vortex core and bubble-type recirculation zone appear. In this flow regime, large-scale vortex structures of spiral shape are found. The contribution of coherent structures to the fluctuations of velocity and temperature is analyzed for a strongly swirling jet by using Spectral Proper Orthogonal Decomposition (SPOD) method and spatial Fourier transform. It is found that the strongly swirling jet for H/d = 1 provides most effective overall cooling of the surface for the considered flow configurations.
Unsteady forced convection heat transfer of a stationary and rotating sphere: Experimental Investigation
Authors: Abed A H , Shcheklein S E
Published: December 2020

Unsteady forced convection heat transfer of a stationary and rotating sphere in an open-loop air system was experimentally investigated with an aim to evaluate the influence of sphere rotation rate on the heat transfer enhancement. A special-purpose conical diffuser having a circular cross-section with constant divergence angle has been carefully designed and adopted as a passive rotating technique. The effect of inlet Re number, non-dimensional rotational speed, and initial surface temperature on heat transfer enhancement are examined. It is observed from the comparison made that there are significant differences between the stationary and rotating sphere of heat transfer behavior. The experimental results of heat transfer behavior in terms of heat flux q and Nusselt number Nu, respectively, expose that q decreases with increase of non-dimensional rotational speed, while Nu increases with the increase of non-dimensional rotational speed around 600%.
Effective heat transfer surfaces of tubes and plates with spiral vortex generators – inclined oval-trench dimples
Authors: Isaev S A , Son E E , Leontiev A I , Nikushchenko D V , Sudakov A G
Published: December 2020

Numerical simulation of laminar heat transfer enhancement at the hydrodynamic stabilization length of the tube with 8 inclined longitudinal oval-trench dimples (OTDs) in the transformer oil flow has revealed an optimal inclination angle of dimples, at which a value of thermal and hydraulic performance (THP) is achieved. Heat transfer of a dimpled tube increases by a factor of 28 in comparison with a smooth tube at practically invariable hydraulic losses. Heat transfer enhancement is calculated in turbulent air flow around a flat plate with a package of 16 one-row dimples inclined at an angle of 60° on the longitudinal section of 40 in length and 4 in width under the symmetry conditions at the side boundaries of the plate section and at a dimple step of 2.4. The dimple is 1 in width, 4.5 in length, and 0.2 in depth. Its rounding radius is 0.3. The boundary layer thickness at the section inlet is 0.175. The effect of abnormal separated flow intensification and heat transfer enhancement in dimples has been confirmed. (f/f

pl
)min=-3, (Nu/Nu
pl
)max = 4. Relative heat transfer grows by a factor of 1.43 in comparison with the smooth plate and the drag coefficient increases by a factor of 2.08. However the thermal and hydraulic performance defined in terms of heat load growth is 1.12.
Heat transfer at the stagnation point of the impinging laminar jet
Authors: Lemanov V , Matyunin V , Travnicek Z
Published: December 2020

Heat transfer of an impinging axisymmetric jet at low Reynolds numbers (Re = 250-5000) at the obstacle stagnation point was studied experimentally. An air jet from a long tube was flowing onto a flat heated plate at a constant wall temperature. The distance from the jet beginning to the obstacle was h/d = 20. A connection of thermal parameters (averaged and pulsating) at the stagnation point for the flow at the initial cross-section of the jet was established. For the laminar flow, an increase in heat transfer of more than 200% was observed in the jet in comparison with the turbulent flow. Comparison of the obtained data on heat transfer revealed a significant discrepancy with the well-known correlation formula for impinging jets.
Calculation of wind flows in residential areas and assessment of their impact on pedestrian comfort
Authors: Meshkova V D , Dekterev A A , Gavrilov A A , Filimonov S A , Litvintsev K Yu , Gavrilov A A
Published: December 2020

This article presents the results of numerical modeling of wind flows around a microdistrict. The distribution of suspended solids of 50 and 100 microns in urban environments is considered. The characteristic of urban development in terms of a comfortable stay of people is given.
Building a fínite-difference mesh and selecting a turbulence model for numerical simulations of a vortex tube in OpenFOAM software
Authors: Mikhaylenko C I
Published: December 2020

In the article, the usability of standard two-parameters models of turbulence for numerical simulation of a vortex tube is discussed. Both k − ε and k − ω turbulence models were checked for subsonic air flows into the vortex tube channel. The main attention was paid to the development of the mesh, the simplicity of the implementation of simulation, and the physical concordance of the model results. Simulations performed by rhoPimpleFoam and sonicFoam solvers using k-ε and k-ω turbulence models gave similar results. The choice was made in favor of the k − ε model.
Experimental study of hydrodynamics and heat transfer of impact jet with chevrons
Authors: Nebuchinov A S
Published: December 2020

Using modern panoramic optical measurement methods, a comprehensive experimental study of the flow structure and heat transfer in a submerged impact jet with and without chevrons was carried out. A detailed study of the influence of the presence of a flat athwart-oriented surface on the structure of the chevron jet flow on convective heat transfer was carried out. In the case of a jet with chevrons, the velocity values at the surface are shown to exceed the values of the standard round jet, and the pulsations are more intense and more uniform near the impact surface, which, accordingly, affects the heat transfer on the target. The increment in the average intensity of heat transfer of the chevron jet reaches 24%, compared with the round jet. The reason for the increment in the heat transfer coefficient is due to an increase in the number of chevrons.
Influence of deltoid tabs on flow dynamics and heat transfer in the separation region behind a back-facing step
Authors: Terekhov V I , Dyachenko A Yu , Zhdanov V. L. , Smulsky Ya J , Sharov K. A.
Published: December 2020

The results of an experimental study of the influence of deltoid tabs on flow dynamics and heat transfer in the separation region behind a back-facing step at Re = 4000 are presented. The studied tabs are triangular in shape with a height of 6 mm. The transverse pitch of their arrangement varies. The flow pattern behind a ledge with mounted tabs, whose structure differs significantly from the flow pattern behind a classical step, is obtained. The presence of tabs brings the maximum heat transfer region closer to the step, while with a decreasing pitch between them the vortex generators become more effective.
Influence of recessing nozzle extent on a process of heat exchange in the combustion chamber of a solid fuel rocket engine
Authors: Benderskyi B Ya , Chernova A A
Published: December 2020

This paper considers issues of numerical simulation of the spatial gas dynamics and heat transfer in the pre-nozzle volume of the combustion chamber of a large solid-fuel rocket engine. It is investigated the effect of the degree of recessing of the nozzle specifying the ratio of flow rates of a gas through the channel and the supra-nozzle gap of the processes in the pre-nozzle volume. An analysis of a topology of the flow structure and thermophysical processes near inlet surface of the recessing nozzle was performed. The distribution of the heat transfer coefficient equation on the inlet surface of the recessed nozzle and a criterial for the estimation of heat transfer depending on topological features on the surface of the recessed nozzle are obtained.
Effect of hydrodynamic coherent structures on local mixing in a model GT-burner
Authors: Lobasov A S
Published: December 2020

Turbulent mixing and swirling flow structure in model GT-burner at atmospheric pressure have been investigated (Re = 5000) by using a combination of the particle image velocimetry and planar laser-induced fluorescence methods. Based on the measurements of the velocity fields by a stereo PIV in combination with acetone-PLIF, three-components of turbulence kinetic energy, Reynolds stresses and turbulent fluxes are evaluated. Contribution of large-scale helical vortex structures to the local mixing has been evaluated by snapshot POD method based on singular value decomposition. It was found that helical vortex structures correspond to the vortex core, spiraling around the central recirculation zone. In the case of supply fuel via central channel, the formation of a secondary vortex structure located between the fuel jet and the recirculation zone is observed, contributing to the mixing of fuel with air.
Temperature measurements in a Bunsen flame by planar laser-induced fluorescence
Authors: Tolstoguzov R V
Published: December 2020

The article presents the results of measuring the temperature distribution parameters based on planar laser-induced fluorescence (PLIF) of the hydroxyl radical (OH) upon excitation of the transition (1–0) of the A2∑+ – X2∏ system. Thermometry is based on registration of the ratio of the radiation intensity of the transition (2–0) and transitions (0–0), (1–1). For the most frequent excitation lines Q2(7), Q1(8), R1(14), P1(2), numerical simulation of fluorescence spectra was performed using the LASKIN software. In this work, the measurement procedure for the laminar pre-mixed Bunsen flame of a methane-air mixture was experimentally worked out. It was shown that the maximum sensitivity of the signal to temperature changes is achieved when the Q1(8) transition is excited. It was found that quenching of fluorescence has a negligible effect on the accuracy of temperature measurement.
On the Phases’ Distribution in Packed Columns
Authors: Boyadjiev Chr B , Dzhonova D B , Stefanova K V , Panyovska St P , Popova-Krumova P G , Pavlenko A N , Zhukov V E , Slesareva E Yu
Published: December 2020

Packed columns are typical apparatuses for industrial separation processes which are important in fuel and energy production and reduction of harmful emissions in the atmosphere. The efficiency of the processes in them is strongly dependent on the regular distribution of phases. The liquid and gas maldistribution has been the subject of long intensive investigations. The formation of a liquid wall flow has been found to be one of the main factors for the large-scale radial irregularity of liquid and gas distribution. The prediction and control of this phenomenon is still unsatisfactory. Our work suggests a new approach for evaluation of the wall flow in countercurrent absorption with random packings. It uses simple mathematical apparatus and is based on experimental data of the wall flow along the column height. It allows gaining knowledge about the liquid flow and evaluating the wall flow volume as a criterion of efficiency for comparison of packings. The model is demonstrated by a case study with data for metal Pall rings.
Cavitation streamlining of a round cylinder in the critical range
Authors: Dobroselsky K G
Published: December 2020

The paper presents experimental results on the transverse cavitation streamlining of a circular cylinder by a turbulent water flow in the critical range of Reynolds numbers determined on diameter. Using the PIV method, averaged velocity fields are obtained. Their vector patterns serve to determine the lengths of the reverse flow and the distance between vortices in the near wake behind the cylinder. The presence of a minimum of spatial characteristics of the vortex zone for the initial cavitation modes is shown. Initial cavitation, transient modes, and developed cavitation are determined for different flow rates. The beginning of cavitation is found to depend on the Reynolds number. With smooth decrease in static pressure in front of the cylinder, critical anomalous phenomena, probably related to the rearrangement of cavitation modes, are detected in very narrow range. Vortex shedding from the cylinder surface is found to occur quasi-periodically despite the possibility of simultaneous shedding and breakdown of vortices.
The effect of intermittency and damping on heat transfer of the flowing down turbulent liquid films
Authors: Geshev P I
Published: December 2020

The model of calculation of thickness and heat exchange coefficient of turbulent film moving under the action of gravity and tangential friction stress of gas flow is constructed. The purpose of the work is to include additional damping caused by the turbulence intermittency and damping characteristic for small Reynolds numbers in the previously proposed simple model of the turbulent viscosity with the cubic law of attenuation in a viscous sublayer and with logarithmic velocity asymptotic away from the wall. The deviation of the calculation results from the experimental data available in the literature decreases when the additional damping is introduced.
Numerical modeling of a thin liquid layer flow on an inclined substrate based on classical convection equations and generalized conditions at the interface
Authors: Rezanova Ekaterina
Published: December 2020

The flow of a thin layer of a viscous incompressible liquid along an inclined non-uniformly heated substrate is investigated in the two-dimensional case. Evaporation is taken into account at the thermocapillary interface. The system of Oberbeck-Boussinesq equations is used as a mathematical model. The kinematic, dynamic and energy conditions generalized for the case of a nonzero mass flux are assumed to be fulfilled at the interface. The value of the local mass flux is determined using the Hertz-Knudsen equation. Solutions to problems for the main terms of power decomposition of a small parameter of the problem are obtained. The evolution equation to determine the position of the interface is obtained. A numerical algorithm for solving the problem is constructed. The problem of periodic runoff of an incompressible liquid layer is considered. The effect of additional terms in the energy condition on the dynamics of the thickness of the liquid layer is studied.
Experimental study of pressure drops in multichannel microchannel heat exchanger at adiabatic two-phase flow of R134a with condensation
Authors: Shamirzaev A S
Published: December 2020

The pressure drop in the heat exchanger with parallel microchannels with throttling of the flow at the inlet and outlet of the heat exchanger was investigated. The experiments were carried out during condensation of the two-phase flow of R134a and under adiabatic conditions in the mass flow range from 200 to 900 kg/m2s. The pressure gradient in microchannels was determined from a change in the saturation temperature under adiabatic conditions. The obtained data were compared with the known relations for calculating the pressure drop taking into account the sudden expansion and constriction of the flow.
Heat and mass transfer during water film evaporation in a horizontal channel with a cocurrent flow of moist air
Authors: Gorbachev M , Terekhov V
Published: December 2020

In this paper, we consider the issues of modeling of joint processes of heat and mass transfer during evaporative cooling of a laminar flow of moist air in a flat horizontal channel, taking into account the finite thickness of the water film. Numerical simulation of processes is based on solving the system of differential equations in boundary layer approximation and in two-dimensional formulation. The research is conducted in the range of input parameters: temperature T
0 = 10 ÷ 50 °C, relative humidity φ0 = 0 ÷ 100 %, and Reynolds number Re = 50 ÷ 1000 at atmospheric pressure. The influence of the Reynolds number and relative humidity on the change of local and average thermodynamic and thermohydraulic parameters of flows along the channel length is shown.
Experimental study of the wettability of silicon substrates coated with vertically oriented carbon nanotubes
Authors: Kochkin D Y , Kurenya A G , Zaitsev D V , Kabov O A
Published: December 2020

The experimental study of the wettability of silicon substrates coated with vertically oriented carbon nanotubes is conducted. It is found that carbon nanotube coatings are superhydrophobic and have small hysteresis. Heat treatment of the carbon nanotube coatings significantly reduces the receding contact angle and virtually doesn’t change the advancing contact angle. It should be noted that the thickness of the carbon nanotube coatings doesn’t significantly affect the substrate wettability.
Numerical study of the processes in the combustion chamber of an engine of diesel generator facilities with valve-inductor generators
Authors: Guzei D V , Minakov A V , Panteleev V I , Platonov D V , Pryazhnikov M I
Published: December 2020

A mathematical model of heat and mass transfer processes in the combustion chamber of diesel generator sets with valve-inductor generators has been developed. The main characteristics of a diesel generator have been analysed within a wide range of operating modes.
Numerical simulation of combined combustion of coal-water and pulverized coal fuel
Authors: Kuznetsov V , Maltsev L , Dekterev A
Published: December 2020

A numerical method for calculating the processes of co-combustion of coal-water and pulverized coal fuel has been developed. The effect of operating parameters on the processes occurring in the combustion chamber at co-combustion of coal-water and pulverized coal fuel has been studied. It is shown that redistribution of air between two stages of the burner affects significantly the temperature distribution in the volume of combustion chamber. Based on the study, it is shown that the addition of microground coal ensures stable combustion of coal-water fuel at combined burning of these two fuels in a flow reactor.
Effect of cavitation treatment of coal-water and composite liquid fuels on their characteristics
Authors: Maltsev L I , Podzharov Yu S
Published: December 2020

The effect of mechano-cavitation treatment of coal-water and artificial composite liquid fuels, based on brown coals and anthracite, on particle size distribution of their coal mass and dynamic viscosity is studied experimentally. It is shown that the treatment of both fuels leads to significant regrinding of their coal mass and a noticeable increase in viscosity.
Creation of energy-efficient and environmentally friendly energy sources on fossil fuels to address global climate issues
Authors: Ryzhkov A F , Bogatova T F , Maslennikov G E , Osipov P V , Nizov V A
Published: December 2020

For industrialized economies, a strategically important area is developing active methods for industrial use of carbon dioxide emissions to produce marketable products. A rational approach to the problem of clean generation should be based on the complete coordination of the output parameters of the CO2discharged from the power plant and the input (working) CO2parameters of the consumer, which will reduce the cost of emissions conditioning, and maintain power plant efficiency. The CO2parameters from fossil fuel power plants and CO2consumers’ potential were analyzed for three main indicators most sensitive to power generation: the amount of CO2, operating pressure, and purity considering the level of technological maturity and market attractiveness. Based on the analysis, three types of energy-industrial symbioses were identified with a cost-effective Power Plant – Consumer model without an intermediate unit for matching input and output parameters of CO2(without a CO2capture and conditioning system). A hybrid solution combining modern IGCC and the latest thermodynamic cycles based on oxy-fuel technologies is offered as a generalized configuration of the energy part of the promising complex. The concept and key technological solutions of the promising energy-industrial symbiosis “Power Generation Unit – CO2-based production” are being developed at Ural Federal University. Such symbiosis ensures the low-cost supply of CO2to industrial consumers using mineralization technology. It will allow utilizing not only technogenic carbon but also ash, slag, and construction industry waste to produce marketable products (cement, concrete, and other materials).
On the similarity of traditional and cluster jets during supersonic gas outflow into flooded space
Authors: Dubrovin K A , Zarvin A E , Rebrov A K , Chinenov S T , Borynyak K I , Yaskin A S , Kalyada V V
Published: December 2020

Annotation. The visualization of gas flows expanding from supersonic nozzles into flooded space under the cluster formation conditions is considered. The technique of exciting the supersonic flow by a well-focused high-voltage electron beam is applied in conjunction with the scanning equipment for the gas objects. The reasons for the secondary cluster jet formation in a flow of easily condensing gases are discussed. A comparison is made between the formation of a traditional spindle-shaped jet and a secondary cluster one. The measurement results of the diameters of the traditional and cluster jets in maximum sections, obtained by the photometry method, are presented. It is shown that for the characteristic sizes of cluster jets of condensing gases, the dependence on parameters proposed by Sherman and Ashkenas is applicable in the entire range of the studied stagnation and background pressures. The similarity of the formation processes of traditional monomeric jets and secondary cluster jets under the conditions of developed condensation of the initial supersonic flow is supposed.
Deposition of diamond from the jet activated in the microwave discharge of gases
Authors: Emelyanov A A , Plotnikov M Yu , Rebrov A K , Timoshenko N I , Yudin I B
Published: December 2020

The present work is devoted to a numerical and experimental investigation of the effect of conditions of methane decomposition on the growth of diamond structures during gasjet deposition. The results of experiments on the diamond gas-jet synthesis from methane and hydrogen mixture flows are presented. The direct simulation Monte Carlo method in cylindrical geometry for numerical analysis of these experiments is applied. A one-dimensional approach based on the solution of equilibrium chemical kinetics equations is used to analyze gas-phase methane decomposition. The conducted research has shown that at a decrease in methane decomposition time in the absence of high temperatures of the fed mixture it is possible to receive higher rates of growth of diamond structures. The obtained results can be useful for optimization of gas-dynamic sources of activated gas diamond synthesis.
A friction factor in rectangular microchannel of 100 μm depth
Authors: Gluzdov D S , Gatapova E Ya
Published: December 2020

The dependence between the shear stress and integral flow parameters such as fluid flow rate still remains unclear for different microchannel geometries. We present results of the numerical simulation of the 3D fluid flow in a microchannel with a rectangular cross section. Basing on the experimental measurements of the pressure drop the fluid flow and the shear stress are analyzed in detail giving the correlations for the friction factor. The results show that the shear stress for a numerical calculation can be estimated using friction factor from the well-known formula with a slight deviation due to wall and corner effects which can be important with the reduction of microchannel size.
Effect of the inlet flow rate ratio on liquid efficiency in a T-shaped micromixer at low Reynolds numbers
Authors: Kravtsova A Yu , Kashkarova M V , Ianko P E , Bilsky A V , Kravtsov Y V
Published: December 2020

The effect of the ratio of inlet flow rates on the flow structure and efficiency of liquid mixing in a T-shaped micromixer was studied at low Reynolds numbers using the method of particle image velocimetry and laser-induced fluorescence techniques. It was found that under the stationary flow regimes, the maximum efficiency of liquid mixing is 0.86 at Re = 186 and inlet flow ratio (R) of 1. The maximum dimensionless value of the longitudinal component of the mean flow velocity (up to 2.0) is achieved for the cases with the smallest and largest inlet flow ratio, that is, at R = 0.03 and R = 1.
Experimental study of droplet detachment from liquid film surface by a co-current flow inside the nozzle stagnation chamber
Authors: Prikhodko V G , Yarygin V N , Yarygin I V
Published: December 2020

The paper presents the results of an experimental study on the interaction of near-wall liquid film with the co-current gas flow in the convergent channel. Conditions for transition (co-current gas flow velocity and liquid flow rate) of near-wall liquid film from annular flow mode to annular-dispersed flow accompanied by a detachment of droplets from the interface are elucidated.
Laboratory simulation for single and block supersonic jets
Authors: Zarvin A E , Krylov A N , Yaskin A S , Antipova M S , Kalyada V V , Gerasimov Y I , Dubrovin K A , Khudozhitkov V E
Published: December 2020

Model experimental studies are presented for the flow field of a single jet, the flow parameters of a block jet, the pressure distribution on the bottom screen, and the parameters of the jet flow from a model nozzle. When expanding into a vacuum and/or a highly rarefied medium, the conditions for reproducing the relative gas pulse value of the full-scale nozzle block section are met. It is shown that when using specific similarity criteria, it is possible to experimentally model the supersonic jet outflow processes of space vehicles on small-sized laboratory vacuum installations, similar to the one created at Novosibirsk State University. Simulation results using spectral density measurements based on the glow excited by a focused electron beam, longitudinal and transverse jet density profiles obtained using modern scanning technology, as well as measurements of bottom pressure near the nozzle block are given. The possibilities and features of each applied registration method are discussed.
Thermophysical properties of the radioactive graphite-nitrogen system
Authors: Barbin N M , Shavaleev M R , Terentyev D I , Dalkov M P
Published: December 2020

This article presents the thermophysical properties of the radioactive graphite – nitrogen system, which can be used as reference data to determine the operating parameters of the high-temperature processing method.
Linear thermal expansion coefficient of porous stainless steel
Authors: Kozlovskii Yu M , Stankus S V , Igumenov I K
Published: December 2020

The experimental results of the thermal expansion study of porous steel 12KH18N9TL in the temperature range 293–1173 K are presented. An anomalous change in the linear thermal expansion coefficient is found in the vicinity of 550 K. The temperature dependences of the thermal properties before and after heat treatment sre obtained and reference tables of recommended values are calculated.
Measuring the diffusion coefficient of single-wall carbon nanotubes in liquids
Authors: Rudyak V Ya , Tretiakov D S
Published: December 2020

This work is devoted to the experimental study of the diffusion of single-walled carbon nanotubes in liquids. The mass concentration of nanotubes varied from 0.00001 to 0.15. As the base fluid, water is used with the addition of two different surfactants: polyvinylpyrroli-done and sodium dodecylbenzenesulfonate. The concentration of surfactant is two times the concentration of nanotubes. The measurements are performed using the dynamic light scattering method. The diffusion and sizes of surfactant molecules have been preliminary studied. The diffusion coefficient of carbon nanotubes are investigated. Using these data the size distributions of nanotubes are obtained. The dependence of diffusion coefficients on the concentration of carbon nanotubes is examined.
Studying in-vessel component materials under heat and plasma loads relevant to fusion installations
Authors: Dedov A V , Budaev V P , Komov A T , Fedorovich S D , Varava A N , Zakharenkov A V , Karpov A V
Published: December 2020

The results of studies of materials under extreme thermal and plasma-beam loads, carried out to justify existing technological solutions in the design of thermonuclear reactors, are presented. The study of materials under plasma and beam loads and the intensifying heat transfer of in-vessel cooled components of fusion devices is reported. Tests of limiter and divertor mock-ups irradiated with high heat fluxes in electron beam and plasma facilities are described. Methods for cooling in-vessel components using advanced approaches with dispersed gas-liquid flow for heat removal, including at loads of up to 15 MW/m2 have been developed and tested.
Experimental study of dissociation of double gas hydrate at various combustion methods
Authors: Morozov V S
Published: December 2020

The dissociation during combustion of a propane-methane gas hydrate double powder is experimentally investigated. Gas hydrate combustion is implemented in four ways: 1) induction heating; 2) radiation and convective heating in a muffle furnace; 3) combustion without forced gas flow; and 4) combustion in the presence of forced air convection u
a. The maximum J is achieved by burning granules of gas hydrate powder on a metal surface with induction heating, where J is the specific dissociation rate. The minimum of J corresponds to the combustion of a layer of gas hydrate powder in the absence of forced air flow. With an increase in the velocity air convection u
a from 0 to 1.2 m/s the J increases and reaches a maximum. A further increase in u
a leads to a decrease in J. For u
a > 3.5 m/s combustion does not occur.
Development of the algorithm for the optimization of objects pick up sequence on a conveyor belt
Authors: Seredkin A V , Bobrov M S , Tokarev M P , Gobyzov O A
Published: December 2020

With recent advances in robotics, various methods and systems for robotic movement planning have gained popularity. In particular, the problem of planning of pick and move operations for the robotic sorting cells has drawn certain attention because new strategies and algorithms become a necessity as a robotic sorting systems application area extends. In the present work, a new algorithm for optimization of sorting operation sequences is proposed and results of its testing on a computer simulation are presented. The algorithm is based on the state tree search method and is aimed for performance improvement of the systems in which the input load can exceed the capacity of the robotic manipulator.
The Study of Self-Heating Effect of AlGaN/GaN High Electron Mobility Transistors Based on TCAD
Authors: Fang Zhicheng
Published: December 2020

As the third-generation semiconductor material, GaN has the characteristics of large forbidden band width and high electron mobility. The AlGaN/GaN high electron mobility transistors (HEMTs) have also attracted attention in recent years. In this paper, the effect of self-heating on device degradation was explored through theoretical analysis and software simulation. Firstly, Silvaco TCAD was used to establish an AlGaN/GaN HEMT single heterojunction model. Then, its self-heating effect was explored by simulation. Besides, it was compared with the theoretical analysis results. The control experiment method was used to compare the I-V output characteristic curve of the device when the self-heating effect was considered, and the relationship between the lattice temperature and the device degradation was researched. According to the research result, when the device is affected by the self-heating effect, the electrical performance of the device degrades obviously due to the increase of lattice temperature.
Research Progress of Gold Core-shell Structured Nanoparticles in Tumor Therapy
Authors: Zhang Ziyan
Published: December 2020

In previous research, the role of gold nanoparticles in tumor photothermal therapy and radiotherapy has attracted the attention of researchers. However, its limited photothermal conversion efficiency and inevitable biological toxicity restrict its further application. With the development of the field of nanomaterials, researchers have discovered that combining gold into core-shell structured nanomaterials can exhibit many surprising properties and has great potential in the field of tumor therapy. This article systematically reviews the progress of gold core-shell structured nanomaterials in the field of tumor therapy in recent years. In this paper, the progress of gold-core-shell nanomaterials in the field of cancer treatment in recent years is reviewed systematically, and the characteristics, preparation methods and deficiencies of gold core-shell nanoparticles are introduced respectively. Although gold core-shell nanoparticles have a good application prospect due to their low toxicity and good biocompatibility, a lot of research work is still needed to solve the problems such as aggregation, photothermal conversion efficiency and large-scale production.
A New Magnetic levitation System for Pipeline Inspection
Authors: Wang Ao , Zhang Yan
Published: December 2020

Through simulation design and simulation calculation, a new magnetic suspension system for pipeline detection is proposed. The system is convenient to carry pipeline detection device and realize the detection of pipeline interior. In this paper, the theoretical principle of the system is discussed, the model is simulated by using the simulation software, and the control method of the system is analyzed theoretically.
The Effect of Bionic Brake Drum Point Unit Body on Friction and Wear of Brake Pad
Authors: Hu Haiyan , Yang Haiyang , Yang Jiandong , Wang Qingnian , Zhou Ti
Published: December 2020

In this paper, the elasticity theoretical analysis has been used to analyze the interaction between the point unit body on the bionic brake drum and the brake pad. Through the analysis, the contact stress distribution law of their interaction has been obtained, and the change in friction and wear of brake pad based on the point unit body is calculated according to the stress distribution law. Only considering the change of the surface feature regardless of other factors, the friction and wear of the point unit body on the brake pad has increased by more than 50%. Based on the research, it is indicated that the small convex point unit bodies are added on the surface of the bionic brake drum, which make the contact surface between the brake drum and the brake pad no longer the original plane contact, and the pressure and direction between the contact surfaces are different. In addition, even if the external pressure remains unchanged, the contact pressure between two surfaces will be increased, thereby increasing the friction and wear of the brake pad.
Numerical and experimental study of buckling behavior of a composite hat-stiffened panel under in-plane shear
Authors: Sun Zhenya , Lei Zhenkun , Bai Ruixiang , Zhang Cong
Published: December 2020

The in-plane shear buckling behavior of a composite hat-stiffened panel is studied by the combination of experimental and numerical analysis. The buckling morphology changes of the hat-stiffened panel during in-plane shearing were monitored and measured by using the fringe projection profilometry and 3D digital image correlation. The in-plane shear buckling load, buckling modes, and failure load of the hat-stiffened composite panel were predicted by using the finite element numerical simulation. The buckling evolution process and failure mechanism of the composite hat-stiffened panel under in-plane shear can be effectively revealed by numerical and experimental investigation.
A distinct sub-seasonal modulation in the Atlantic-originated atmospheric teleconnection influence on East Asian monthly climates
Authors: Ham Yoo-Geun , Lee Se-Gun , Sung Mi-Kyung
Published: December 2020

The strong sub-seasonal modulation in the atmospheric teleconnection between the North Atlantic and East Asia during boreal winter has been examined. Negative precipitation anomalies and corresponding transient eddy vorticity fluxes over the mid-latitude Atlantic induce a wave packet that leads to cold temperatures over northern China, Korea, and Japan. This relationship is significant for the anomalies averaged from mid-January to mid-February, while it is less for January or February. In mid-January segment, the transient vorticity forcing (TVF) over the mid- to high-latitude Atlantic is the strongest, and consequently, the atmospheric response strengthens the anticyclone over central Eurasia to facilitate strong development of the Siberian High as well as cold temperatures in East Asia. Model simulations support the sub-seasonal linkage modulation through amplitude change of the TVF. It is proposed that intensified atmospheric baroclinicity associated with the deepened North American trough is responsible for the pronounced TVF and downstream influences in mid-January.
Theoretical analysis of fracture in non-linear elastic functionally graded beam of linearly changing thickness with three longitudinal cracks
Authors: Rizov V
Published: December 2020

The present paper is focussed on fracture analysis of a functionally graded nonlinear elastic cantilever beam structure with three longitudinal cracks. The cross-section of the beam is a rectangle. The beam height increases linearly towards the clamped end. The material is functionally graded along the thickness of the beam. The J-integral approach is applied in the fracture analysis. The solutions to the J-integral for the three cracks are verified by deriving of the strain energy release rate. For this purpose, the complementary strain energy cumulated in the beam is differentiated with respect to the areas of the three cracks. A parametric investigation of the longitudinal fracture behaviour of the beam is carried-out by applying the solutions to the J-integral. The effects of the beam geometry, the crack length and the material gradient along the beam thickness on the longitudinal fracture behaviour are evaluated and discussed.
Simulation of steel rod atmospheric corrosion by alternate immersion in salt solution
Authors: Tsonev Veselin , Nikolov Nikolay , Penkov Kamen , Marcheva Yordanka
Published: December 2020

Corroded B235 reinforcing steel rods, which were exposed to an open air environment for 25 years, with a certain specific mass loss, were studied. Test pieces were prepared from them by lathe machining. The test pieces were subjected to accelerated corrosion through an alternate immersion in NaCl solution. The same specific mass loss as on the initial corroded rods was achieved for 52 days. Further the test pieces were cleaned, observed, photographed and tensile tested. The cleaned surfaces and the stress-strain curves of the test pieces were compared with results, obtained from the initial corroded rods. It was found out about the tested steel rods that alternate immersion in salt solution for 52 days is a good simulation of twenty-five-year atmospheric corrosion.
Increasing the safety operation of railway tanks in emergency situations by improving the design of boiler bottom protective elements
Authors: Št’astniak Pavol , Gerlici Juraj , Kravchenko Kateryna
Published: December 2020

This article presents an analysis of the problem of reliability of tank boilers in an emergency event. The designs of the boiler bottom protection and the prevention of wagon crawls on top of each other in collisions are evaluated. An analysis of the requirements for the tank protective elements is performed. A technical solution to improve the protective shield of the bottom is developed. The proposed solution will increase rigidity and strength of the protective shield structure, reduce the risk of damage to the railway tank boiler bottom when the protruding elements of the adjacent wagon collide. The work presents the results of the stressstrain state of the proposed design protective shield in the case of rail car collision and, accordingly, the force impact of 150 kN according to the RID TE25 standard.
Research into the dynamic loading on the carrying structure of a flat wagon with lower center of gravity when transporting firing equipment
Authors: Fomin O , Lovska A , Pavliuchenkov M , Sova S
Published: December 2020

The article presents the study results of the dynamic loading of a flat wagon with a lower gravity center.The authors built a mathematical model that takes into account displacements of a flat wagon loaded with an anti-aircraft installation firing in motion. The solution of the differential equations of motion is carried out by using the Runge-Kutta method. The maximum vertical acceleration was about 5 m/sec2 and almost independent of the fire angle. The horizontal acceleration was about 37 m/sec2. The acceleration values obtained did not exceed the normative ones. The study defined the natural oscillation frequencies for the frame of a flat wagon with lower gravity center. It was established that the critical oscillation frequencies were within the admissible values. The results of the work will contribute to the creation of recommendations on the transportation of military equipment on wagons and the possibility of conducting military operations from them.
Numerical investigation of the mechanical behaviour of a structural element containing a self-healing agent
Authors: Zhelyazov T , Ivanov R
Published: December 2020

This paper presents a virtual experiment on the behaviour of a self-healing material from the family of cement-based composites, that contains a healing agent. A numerical model of a specimen made of a cement-based material, and containing a healing agent is subjected to the loading configuration of the four-point bending test, whereby the forces are applied in a quasi-static way. The response of the healed specimen is compared to the response of a specimen that doesn’t contain a healing agent. For the specimen that contains a healing agent, homogenization techniques are used to determine the characteristics of the equivalent material (cement-based composite / healing agent) in zones where damage and macro-cracking have occurred, i.e., zones in which the healing agent has been activated. The main result of this contribution is the formulation and validation of a numerical simulation approach suitable for modelling the mechanical behaviour of self-healing cement-based composites.