bluuebunny/crossref_metadata_2025_split huggingface dataset:
On coherent structures and heat transfer in strongly swirling impinging jets
Authors: Abdurakipov S , Sharaborin D 
Published: December 2020

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractFor 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

Abstract
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

Abstract
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.