bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat transfer behind the backward-facing step in the presence of longitudinal vortex generators installed at an angle to each other
Authors: Terekhov V I , Dyachenko A Yu , Zhdanov V L , Smulsky Ya J 
Published: December 2021

Abstract
The paper presents the experimental results on the control of heat transfer enhancement behind the backward-facing step at Re = 4000. The flow is controlled by a pair of longitudinal vortex generators (LVGs) installed at the step edge. The pair of vortex generators (VG) consists of two plates positioned symmetrically relative to the flow. The influence of the height, the angle of VG installation relative to the flow, the distance between VG pairs and the shape of the plate on local and average heat transfer is investigated.
Parametric study of cone angle influence on bubble vortex breakdown onset in laminar conical flow at various swirl numbers
Authors: Skripkin S G 
Published: December 2021

Abstract
The current work studies a swirling laminar viscous pipe flow with a controllable swirl number and varying pipe divergence cone angle. Such flows are widely used in various engineering applications. When a certain level of flow swirl is reached, a phenomenon called vortex breakdown occurs, the characteristics of which depend on the intensity of swirling of the flow and the Reynolds number. However, in addition to these two parameters, an important influence is exerted by the pipe opening angle, which often does not allow generalizing the results obtained in the pipe flow with even slightly different angles. Since experimentally it is quite difficult and expensive to change the pipe angle, especially considering the water as working fluid, this issue could be solved using CFD techniques. Using the design study, 63 different combinations of S and α are considered. The effect of the pipe divergence angle on the position of the bubble vortex breakdown and its properties is demonstrated. It is shown that there is a nonlinear relationship between the position of the bubble breakdown onset and the minimum value of the axial velocity at the axis depending on the opening angle of the cone.
Investigating a pulsating flow in the smooth channel and at the bifurcation section with regard to the popliteal artery hemodynamics
Authors: Molochnikov V M , Mikheev N I , Mikheev A N , Paereliy A A , Goltsman A E 
Published: December 2021

Abstract
Experimental setup is described. Pulsating flow in a smooth channel, and steady and pulsating flows at a bifurcation section simulating the distal end of an artery anastomosis at different flow rates in the main and outflow channels are studied. Indications of laminar-turbulent transition are observed in the near-wall region of the smooth channel. Mechanisms of turbulization of the near-wall region in the pulsating flow are suggested. Vortex flow structure in the bifurcation section is analyzed.
Characteristics of the circular subsonic laminar jets flow with an initial Poiseuille profile
Authors: Lemanov V V , Terekhov V I , Sharov K A , Shumeiko A A 
Published: December 2021

Abstract
In this work, the experimental data are compared with the version of the “strong” jet (Re ≫ 1) of the exact Landau-Squire solution. The experiments were performed for a submerged air jet flowing out of a tube with a diameter of D = 3.2 mm and a length of more than 100D at a Reynolds number equal to Re = 436. The initial conditions in the jet are the Poiseuille velocity profile, the level of velocity pulsations is less than 1%. Measurements were carried out using a hot-wire anemometer. It is shown that satisfactory agreement with theory is achieved at distances from the tube starting from x/D = 5.6 and up to the zone of transition to turbulence (x/D > 35). Turbulence along the jet axis will increase from 1% to 2.5%, while in the mixing layers it increases to 4.7%.
Non-stationary convective heat transfer in an air synthetic impinging jet. Experiment and numerical simulation
Authors: Lemanov V.V. , Pakhomov M.A. , Terekhov V.I. , Travnicek Z. 
Published: December 2021

Abstract
An unsteady local heat transfer in an air synthetic non-steady-state jet impingement onto a flat plate with a variation of the Reynolds number, nozzle-to-plate distance and pulses frequency is experimentally and numerically studied. Measurements of the averaged and pulsating heat transfer at the stagnation point are conducted using a heat flux sensor. The axisymmetric URANS method and the Reynolds stress model are used for numerical simulations. For local values of heat transfer, zones with the maximum instantaneous value of heat flux and heat transfer coefficient are identified. The heat transfer increases at relatively low nozzle-to-plate distances (H/d ≤ 4). The heat transfer decreases at high distance from the orifice and target surface. An increase in the Reynolds number causes reduction of heat transfer.
Quasi-periodic forces and conditionally averaged characteristics of unsteady cavitation flow around a hydrofoil
Authors: Ivashchenko E I , Hrebtov M Yu , Mullyadzhanov R I 
Published: December 2021

Abstract
Large-eddy simulations are performed to investigate the cavitating flow around two dimensional hydrofoil section with angle of attack of 9° and high Reynolds number of 1.3×106. We use the Schnerr-Sauer model for accurate phase transitions modelling. Instantaneous velocity fields are compared successfully with PIV data using the methodology of conditional averaging to take into account only the liquid phase characteristics as in PIV. The presence of two frequencies in a spectrum corresponding to the full and partial cavity detachments is analysed.
Experimental investigation of pressure fields in a single trench dimple
Authors: Yan Lun N , Baranov I N , Terekhov V I , Chokhar I A 
Published: December 2021

Abstract
The paper describes the technique and results of an experimental investigation of the pressure distribution over the surface of an oval trench dimple (OTD). The trench dimple in cross-section is a cylindrical segment on one of the flat channel walls. The experiments were carried out at a constant Reynolds number Re
D
= 3.2 · 104 and variation of the inclination angle relative to the longitudinal axis of the channel in the range φ = 0 – 90°.
Experimental study of flow dynamics of a sweeping jet in a slot channel
Authors: Shestakov M V 
Published: December 2021

Abstract
In recent years, fluidic oscillators have been actively applied as devices for flow control in the field of aero and hydrodynamics. This study aims to investigate the structure of a flow of sweeping jet ejected from a fluidic oscillator into a confined area – slot channel. Dynamics of sweeping jet flow are investigated using the PIV method with high temporal resolution. The effect of the Re number on the sweeping jet oscillation frequency was studied in the range from 1 500 to 8 000. Linear frequency dependence on Re number was obtained. Bounding walls affect the dynamics of sweeping jet flow that leads to a change of average velocity field. For low Re numbers, obtained results are in good agreement with the results of other studies.
Electroplasma processing of medical and biological waste
Authors: Domarov P V , Anshakov A S , Faleev V A 
Published: December 2021

Abstract
The article presents an experimental study of biomedical waste in the form of disposable masks. The study was carried out on a laboratory plasma arc installation with a capacity of 20 kg/h. During the experiments, the most important technological parameters were studied: the composition of the exhaust gases, the dependence of the exhaust gases on the temperature in the chamber of the plasma arc furnace, etc.
Non-equilibrium process of transfer of momentum in medium with relaxation microstructure
Authors: Popov V I , Kuznetsov A V 
Published: December 2021

Abstract
The non-equilibrium process of transfer of the momentum of polymer media with an evolving nonequilibrium relaxation microstructure is considered. For the basic conditions of deformation, the regularities for the structural and dynamic components of the stress tensor with conjugate forces are obtained and analyzed, which are consistent with experiment.
Temperature measurements in a swirling impinging flame by planar laser-induced fluorescence
Authors: Tolstoguzov R. V. 
Published: December 2021

Abstract
This article presents the results of approbation of the method for registering temperature distributions based on the planar laser-induced fluorescence of a hydroxyl radical (OH) when the band (1-0) of the A2Σ+–X2Π system is excited. The thermometry is based on the recording the ratio of the radiation intensity of the band (2-0) and the bands (0-0), (1-1). Numerical modelling of fluorescence spectra is performed using the LASKIN program for the most frequent excitation lines Q2(7), Q1(8), R1(14), P1(2). The temperature field of a swirling flame, impinging on a flat cold surface, for H/d = 1, 2 and 3 calibres (where H is the distance between the jet nozzle and the surface, d is the outlet diameter of the nozzle) is obtained. The results of the work demonstrate that when the transition Q1(8) is excited, the ratio of the intensity of fluorescence signals for the band (2-0) and the bands (0-0), (1-1) provides a high sensitivity to temperature and is not significantly affected by fluorescence quenching. The report also concludes that this method can be implemented using single pulsed laser illumination and is effective for the detecting the position of flow recirculation zones and registering hot heat release zones with the combustion products.
Investigation of service life characteristics of hot cathodes in arc plasmatrons
Authors: Anshakov A S , Aliferov A I , Domarov P V 
Published: December 2021

Abstract
Among the applied challenges associated with the use of electric-arc plasma, the most urgent is the erosion of electrodes in plasmatrons, which determine the continuous operation of an electric-plasma device. Investigation results on the thermal state of hot cathodes and their erosion are presented depending on the main defining parameters, namely geometrical dimensions of electrodes, Joule heating, current of the arc discharge, and the gas medium. The conditions for the minimum specific erosion and long service life of tungsten thermionic cathodes are established experimentally.
Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields
Authors: Severin A S , Timoshevskiy M V , Ilyushin B B , Pervunin K S 
Published: December 2021

Abstract
A new method was developed for statistical analysis of ensembles of instantaneous velocity fields measured by PIV in liquid (continuous phase) to determine the distribution of the vapor phase in cavitating flow. The method is based on two main principles: the absence of tracers used for PIV measurements in vapor, and the statistical independence of individual measurements. This allowed establishing an exponential dependence of repeatability of the vapor phase at a certain point of a cavitating flow. Compliance with this theoretical law was verified using the Pearson chi-square test. All theoretical distributions were divided into several groups depending on the time-averaged local vapor content calculated over the entire ensemble of realizations and the probability of a single event. As a result, dimensions of the stationary part of an attached cavity and the place of detachments of cloud cavities from the hydrofoil surface were determined using the new method of statistical analysis for an unsteady cloud cavitation regime.
The investigation of the height effect of a slit microchannel with a textured wall on its hydrodynamic drag
Authors: Lobasov A S , Minakov A V 
Published: December 2021

Abstract
The numerical investigation of the fluid flow in a slit microchannel with a textured wall was carried out. The effect of the channel height on the hydrodynamic drag coefficient, as well as on the pressure drop in such channel and the effective slip length on the wall for various Reynolds numbers, are presented in the paper. The channel length was 100 µm, and its height was varied from 25 µm to 500 µm. The Reynolds number was varied from 0.1 to 100. The main studied characteristics were compared to the similar ones obtained for a channel with normal walls (no-slip conditions). It was found that the pressure drop in such textured microchannel was lower as compared to a conventional channel for any of its heights and for any Reynolds numbers. The dependences of the relative pressure drop, effective slip length, and drag coefficient on the Reynolds number were obtained for different channel heights. The drag coefficient was described as 20/Re for the average values of the channel height. A correlation that describes the dependence of the friction factor on the Reynolds number for small and large heights of the channel was proposed. The accuracy of the proposed correlation was about 90%.
An experimental study on the subcooled flow boiling pressure drop of R141b in the system of two microchannels
Authors: Shamirzaev A. S. 
Published: December 2021

Abstract
An experimental study of the pressure drop under subcooled flow boiling of the refrigerant R141b in a system with two slotted microchannels was carried out. A copper block with two microchannels 2 mm wide, 0.4 mm deep, and 16 mm long was used as an experimental section for testing. The mass flow rate varied in the range from 1 to 4 g/s, the initial subcooling from 20°C to 50°C. Experimental data show a significant decrease in the pressure drop when the critical heat flux is reached. The experimental data are compared with the model known from the literature. Experimental data show that the occurrence of nucleate boiling incipience at subcooled boiling corresponds to a larger heat flux than that given by the recommended correlation.
Numerical Modelling of Liquid Film Spreading Dynamics over Smooth Vertical Surface under Isothermal Conditions
Authors: Sakhnov A , Volodin O A , Pecherkin N I , Pavlenko A N 
Published: December 2021

AbstractThe paper presents numerical modelling of the liquid film spreading dynamics of the R21 (mol. fraction: 0.9) and R114 refrigerants mixture. We considered an outer flow along a round vertical cylinder at Reynolds number of 104 and various contact angles. The simulation was performed in OpenFOAM software on the basis of the volume of fluid (VOF) method. We have shown that the wetting front deforms at wetting angles of 30 and 50 degrees, and regular jets form. At the same time, it was demonstrated that at the wetting angle of 10 degrees the spreading front has practically a flat shape, but one may see some regular thickenings of the liquid film along the contact line of the front.
Application of the Riemann problem with complex equations of state for modeling three-dimensional flows of real media
Authors: Tenenev V A , Koroleva M R , Chernova A A 
Published: December 2021

Abstract
The paper considers the numerical simulation of spatial flows of real media in safety valves on the basis of the problem of an arbitrary discontinuity breakdown with complex equations of state. The solution is constructed by means of the developed numerical method, which is a modification of the classical scheme by S. K. Godunov and includes various complex equations of state of matter. The Van der Waals equations of state were used to model the flow of real gases, and the Mie-Grüneisen equation was used to describe the flow of a real weakly compressible fluid. It is shown that the proposed numerical schemes allow for modeling fluid and gas dynamic processes in real fluids and gases with shock waves and contact discontinuities and can be used both in areas of classical medium behavior and in areas with non-classical behavior.
Capillary-gravitational waves and storage of liquid CO2 in the oceans
Authors: Derzho O G 
Published: December 2021

Abstract
A theory of capillary-gravitational waves in the transition region between seawater and liquid carbon dioxide in deep oceans is proposed. It is shown that the thickness of the transition layer affects the properties of capillary-gravity waves. The question of the structure and stability of wave disturbances at the interface between seawater and liquefied carbon dioxide is essential for the safe storage of liquefied carbon dioxide in the ocean. This is an important issue on the current agenda in light of global warming.
Nonlinear evolution equation for modeling waves at the boundary of a stratified flow of viscous liquids in an inclined channel
Authors: Arkhipov D G , Khabakhpashov G A 
Published: December 2021

Abstract
The dynamics of perturbations of the interface of a two-layer Poiseuille flow in a flat closed inclined channel is studied. The velocity profiles of wave motion are analytically found neglecting dissipation, dispersion and pumping of perturbations. On the basis of the found solution, a nonlinear evolution integro-differential equation for plane moderately long perturbations of the interface of the liquids is derived. The coefficients of the equation are represented by integrals over the layer thicknesses from functions depending on the stationary flow and perturbation profiles. The equation takes into account viscous dissipation: one of the integrals in this equation corresponds to dissipation in lion-stationary boundary layers, and the other corresponds to the transfer of energy from the flow to the wave. For the case of small flow velocities, the coefficients of the equation are analytically calculated. The equation has also been generalized to the quasi-two-dimensional case when the gradients along the transversal coordinate are small.
Research of pressure pulsations during gas outlet to closed pipe area with liquid and installed disc barrier
Authors: Alekseev M V , Vozhakov I S , Lezhnin S I 
Published: December 2021

Abstract
A numerical simulation of the gas outflow to a closed region filled with liquid with a barrier disk was performed. The calculations were carried out using the VOF method, supplemented by the k-e turbulence model. Calculations were performed for three cases of 100, 200, and 300 mm distances of the disk from the injector with a gas outflow into water and liquid lead. The pulsations of axial pressure on a disk obstacle were investigated. It was found that the maximum pressure during pulsations of the upper gas volume in lead can be greater than the pressure in the gas receiver.
Modeling of nonstationary gas outflow at breaks of subsea gas pipelines
Authors: Lukyanov A A , Alekseev M V 
Published: December 2021

Abstract
Numerical modeling of the outflow of an air jet into water with a guillotine rupture of a pipeline by the VOF method using k-ε and k-ω SST turbulence models was carried out. The calculations were carried out in the axisymmetric approximation. The following phases of the outflow process were calculated: the formation of a large gas bubble at the place of the rupture, its growth, the separation of the bubble from the place of rupture, and the formation of a gas jet behind the bubble. It is shown that the rate of bubble detachment in the calculations by the k-ω SST model is higher than that in the calculation by the k-ε model.
Heat transfer in a centrifugal vortex tube
Authors: Gorelikov E U , Naumov I V , Tsoy M A , Shtern V N 
Published: December 2021

Abstract
The results of an experimental study of the heat flux in a model of a centrifugal vortex apparatus with a lower rotating disk are presented. An experiment considered three cases at a distance between the disks H=R/2 and H=R: “water”, “water-air”, and “water-oil”. Using the colorimetric method, the dependence of the heat flux on Reynolds is shown. The case “water-air” was chosen to evaluate the contribution to heat exchange from the thermocapillary effect (Marangoni) at high Re. For the case of two immiscible liquids of different densities (water-oil), the effect of “centrifugal levitation” is found.
An experimental study of flow boiling heat transfer of zeotropic mixture R32/R134a in a microchannel heat exchanger
Authors: Shamirzaev A. S. 
Published: December 2021

Abstract
This paper presents experimental data on heat transfer of a binary zeotropic mixture of refrigerants R32/R134a in a microchannel heat exchanger with a high specific surface within a range of parameters that is practically important for the development of cooling systems for microelectronics and space technology. The experiments were carried out in a horizontal heat exchanger with one-sided heating of a copper microchannel plate 20x40 mm, containing 21 rectangular microchannels with a cross-section of 335x930 μm, within the range of mass fluxes from 80 to 250 kg/m2s, and at an absolute pressure in the system ranged from 12 to 14 bar. A zeotropic mixture of refrigerants R32/R134a with a molar concentration of the initial mixture of 65%/35% was used as a working fluid. Experimental data were compared with model-based calculations that take into account the influence of changes in the concentrations of components in the liquid and gas phases.
Experience in registration of evaporation of liquid drops on a substrate by the capacitive method
Authors: Kokorin A V , Nazarov A D , Serov A F 
Published: December 2021

Abstract
This paper presents the results of an experimental study of the dynamics of evaporation of nanofluid droplets based on distilled water with a mass concentration of SiO2 nanoparticles of 0.1%, 0.5%, and 7% lying on a metal surface. The drop height was changed over time using original equipment, which is based on an integrated approach to the combined use of capacitive and optical recording methods. The experimental results show that the change in the height of nanofluid droplets with concentrations of 0.1%, 0.5%, and 7% is linear over the main part of the evaporation time interval. A deviation from the linear law is observed at the final stage, at the time interval of complete evaporation. The time for complete evaporation of droplets of nanofluids with a concentration of 0.1% increases by 20%, for droplets with a concentration of 0.5%, it increased by 28% in comparison with the evaporation of droplets of the base liquid. The particle concentration of 7% does not lead to an increase in the evaporation time of droplets in comparison with the evaporation of low concentration droplets. Before the formation of a jelly-like residue of nanoparticles, the evaporation rate of droplets with a particle concentration of 7% is comparable to the evaporation rate of droplets with a concentration of 0.1%.
Numerical studies of the effect of the temperature drop in the crucible - melt - cooled disk system on the shapes of crystallization fronts
Authors: Kislitsyn S A , Berdnikov V S 
Published: December 2021

Abstract
The crystallization process on a cooled disk located on the free surface of a water layer is studied numerically. The influence of thermal gravitational-capillary and mixed convection on the shape of the crystallization front is investigated. In mixed convection modes, the speed of uniform rotation of the disk is set. The calculations were carried out in an axisymmetric formulation of the problem by the finite element method using an adaptive triangular grid and taking into account the latent heat of crystallization and the inverse dependence of density on temperature.