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Thermophysics and Aeromechanics

2022 year, number 5

1.
Direct molecular modeling in physical mechanics. Problems, prospects and new approaches

V.Ya. Rudyak1,2
1Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: gas, liquid, molecular modeling, transfer processes

Abstract >>
The aim of the work is to analyze the existing and used methods of direct molecular modeling of physical processes and phenomena. In particular, methods of molecular dynamics, Brownian dynamics, direct statistical Monte Carlo modeling, and stochastic molecular modeling are discussed. In all cases, the main features of these methods, the accuracy of modeling and development prospects are analyzed. Examples of solving original problems, in particular, modeling of gas transfer coefficients in the volume and nanochannels are considered.



2.
Experimental investigation of instantaneous local separation of the flow in a turbulent boundary layer at various Reynolds numbers

D.I. Zaripov1, A.A. Lukyanov1,2, D.M. Markovich1,2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: flow separation, turbulent boundary layer, particle image velocimetry

Abstract >>
The effect of the Reynolds number on the mechanism of formation of an instantaneous local flow separation that occurs in the near-wall region of a turbulent boundary layer is experimentally studied. The features of application of the high-speed planar PIV method with a high spatiotemporal resolution are discussed. Comparison of the measurement results obtained within a viscous sublayer of a turbulent boundary layer with the results of other studies showed the generality of the mechanism for the formation of an instantaneous local flow separation in the range of dynamic Reynolds number 207 ≤ Re τ ≤ 672.



3.
Local laminarization in a channel with a small narrowing and a heated wall

A.Yu. Sakhnov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk,Russia
Keywords: boundary layer, heat transfer, laminarization, velocity sweep, numerical modeling, negative pressure gradient

Abstract >>
The article presents the results of numerical simulation of the boundary layer of air on a heated surface in the presence of weak acceleration. The numerical model consists of a system of Prandtl equations describing dynamic and thermal processes in the boundary layer, and a κ-ω-γ turbulence model that allows reasonably simulating the laminar-turbulent transition and turbulence suppression. Finite-difference methods were used to solve differential equations. For some calculated cases, the turbulence model was switched off in order to obtain parameters of a known laminar flow. Modeling has shown that in the considered flow conditions, the occurrence and development of a local laminarized region near the wall is possible. In this case, the boundary layer includes the near-wall laminar and external turbulent sections. This nature of the flow leads to a level of friction and heat exchange that correspond to the intermediate flow relative to laminar and turbulent flows under the same conditions.



4.
Development of a method for determining flow parameters in impulse wind tunnels

Yu.V. Gromyko, I.S. Tsyryulnikov, A.A. Maslov
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: high-enthalpy short-duration facility, calculation of flow parameters, method of two thermocouples, velocity, PIV method

Abstract >>
Known approaches to the determination of flow parameters in the test section of impulse wind tunnels are analyzed, and ways towards their improvement are outlined. An algorithm for calculating flow parameters in short-duration supersonic high-enthalpy wind tunnels using the experimental values of pressure in the prechamber, the total pressure behind the normal shock, and the flow velocity and stagnation temperature as a function of time, is developed. It is shown that the results of measurements and calculations using the developed algorithm for determining flow parameters fairly well comply with the calculations of flow parameters based on the gas-dynamic relations taking into account the losses of heat in the working path of the wind tunnel.



5.
LDA-based experimental study of flow crisis in the Ranque-Hilsch vortex tube

I.K. Kabardin
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: vortex tube, Ranque-Hilsch tube, flow crisis, hydraulic jump, LDA method

Abstract >>
The paper discloses the study of flow crisis in the Ranque-Hilsch vortex tube with a squared cross-section channel. Previous studies have found the conditions for developing the hydraulic crisis for air flow in this type of tube. The crisis phenomenon is related to the event when the longitudinal velocity at the nearwall vortex-circulation zone interface approaches the value of velocity for spreading centrifugal waves along this boundary. The paper presents and discusses the new detail results in measuring the kinematic parameters of the crisis flow, including the parameter of velocity pulsation. The evidences of a hydraulic jump neat the exit of the swirl flow to the tube working channel.



6.
Experimental investigation of vortex structure formation in a gas-vortex bioreactor

I.V. Naumov1, R.G. Gevorgiz1,2, S.G. Skripkin1, B.R. Sharifullin1
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Kovalevsky Institute of Biology of the Southern Seas of RAS, Sevastopol, Russia
Keywords: hydrodynamics, closed vortex flow, heat and mass transfer, vortex bioreactors

Abstract >>
The formation of circulation vortex cells in a liquid medium of a gas-vortex bioreactor has been experimentally studied. The study was carried out in an industrial glass bioreactor with a volume of 10 liters and a reactor vessel diameter D = 190 mm. The vortex motion of air was generated by a paddle wheel (activator) when 50 and 80% of the reactor vessel was filled with the model medium. A 65% water solution of glycerol with density ρ = 1150 кг/м3 and kinematic viscosity ν = 15 мм2/с was used as a model medium. To observe the pattern of vortex motion, the method of particle image velocimetry (PIV) was used. It is shown that when the activator rotates, the meridional and circulation motions of the liquid occur simultaneously. Regularities of the vortex motion of the model medium are determined depending on the reactor filling and the intensity of activator rotation. It is found that the cells of centrifugal circulation appear under the interface; with an increase in the activator rotational speed they develop into the depth of the reactor. It is established that centrifugal circulation of liquid develops similarly as it takes place in a closed vortex flow of one liquid and in a system of limited vortex motion of two immiscible liquids.



7.
Numerical optimization of S-shaped intake performance using special cross-sectional profiles

S.H. Sadatpour, A. Madadi, R. Ahadian
Amirkabir University of Technology, Tehran, Iran
Keywords: S-shaped intake, genetic algorithm, artificial neural network, flow uniformity, pressure recovery

Abstract >>
An intake has to provide air for the engine uniformly with minimum total pressure loss. Nowadays, regarding the usage of S-shaped intakes, optimization of these ducts has been considered. Uniform distribution of flow at the compressor inlet directly influences the engine performance, and non-uniformity of flow increases surge occurrence possibility. Flow separation along the duct causes a reduction of pressure recovery and engine thrust force. This research has optimized an S-shaped intake to reduce the total pressure loss and flow distortion. The genetic algorithm and artificial neural networks have been combined to decrease the computational cost. Two optimizations, using different conditions, have been studied. In the first case, by modifying centerline coordinates and area ratio of sections, new geometries have been produced, which have caused an improvement of 32.5 % in pressure recovery coefficient and a decrease of 35.8 % in flow distortion. In the second optimization, the shape of each section has also been changed. Super ellipse, egg-shaped and circular profiles are considered as cross sections of the duct. The second optimization has improved the pressure recovery coefficient by 35.5 % and decreased flow distortion by 39.2 %.



8.
Three-dimensional models of gas-permeable-skeleton high-porosity cellular materials for supersonic aerodynamics

S.V. Kirilovsky, T.V. Poplavskaya, S.G. Mironov, I.S. Tsyryulnikov, I.R. Valiullin, T.S. Militsina
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: supersonic flows, flow control, gas-permeable porous inserts, aerodynamic drag

Abstract >>
Results of numerical simulation of a supersonic (М = 7) flow past a cylinder with a frontal gas-permeable porous insert (porosity 95%, pore diameter 2 mm) installed at angles of attack α = 0÷10° are reported. The numerical modeling was performed based on the solution of three-dimensional Reynolds-averaged Navier-Stokes equations using three skeletal models: a model of intersecting hollow spheres, a model of non-intersecting hard spheres with a random arrangement of pores, and a model consisting of a set of toroidal elements. The calculated data on the drag coefficients and on the lift force of a cylinder with a frontal gas-permeable high-porosity insert are compared with the results of experiments carried out in the T-327 wind tunnel of ITAM SB RAS. A comparative analysis of the results of using three-dimensional skeletal models of highly porous cellular materials for modeling supersonic flows around bodies with gas-permeable porous inserts installed at various angles of attack is performed.



9.
Density and thermal expansion of Fe60Co20Si8B12 alloy in crystalline, liquid, and amorphous states

S.V. Stankus1, I. Subkhankulov2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk,Russia
2Sh. Rashidov Samarkand State University, Samarkand, Uzbekistan
Keywords: FeCoSiB alloy, melt, crystalline and amorphous state, density, thermal expansion, gamma method

Abstract >>
The density and thermal expansion coefficients of polycrystalline, liquid and amorphous phases of Fe60Co20Si8B12 alloy in the temperature range of 293÷1650 K have been measured by the monochromatic gamma-ray attenuation technique. The features of crystallization of the melt and amorphous film have been investigated. Reference tables of properties have been developed, their errors have been estimated, and approximation equations have been obtained.



10.
Heat transfer coefficients of Inconel 617 alloy

A.Sh. Agazhanov, D.A. Samoshkin, Yu.M. Kozlovskii
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk,Russia
Keywords: Inconel 617 nickel alloy, thermal diffusivity, thermal conductivity, laser flash method

Abstract >>
The presented research investigated the thermal diffusivity (α) and the thermal conductivity (λ) of one of the most promising heat-resistant nickel alloys, Inconel 617. The measurements were carried out in the temperature range from 300 to 1475 K using the laser flash method on the LFA-427 setup. The estimated errors of the received data depending on temperature were 2-4% and 3-5% for α and λ, respectively. A comparison with the known literature data was made. The fitting equations for the temperature dependences of the studied properties have been received and a table of reference values has been compiled, which can be used in various engineering and scientific tasks.



11.
On dynamical and thermal behavior of an impinging jet involving a chevron nozzle

S. Horra1, L. Khezzar2, Z. Nemouchi1
1University of Mentouri Brother, Constantine 1, Algeria
2National Polytechnic School of Constantine, Constantine,Algeria
Keywords: impinging jet, chevron, heat transfer, Nusselt number, turbulence model, SST k-omega

Abstract >>
A three-dimensional turbulent round jet impinging on a heated flat plate is investigated numerically. The effects of the nozzle geometry and nozzle-to-plate distance on the dynamical and thermal behavior are explored. A round nozzle and nozzles fitted with either 4 or 6 chevrons are considered. Three nozzle-to-plate distances are studied: H/D = = 2, 4, and 6. The Reynolds number equals 5000. The results show that the chevrons improve the heat transfer near the area of stagnation. This improvement can reach up to 110 % in specific regions. It is also found that the wall heat flux is appreciably non-uniform for the small distance H/D = 2. Degraded heat transfer is recorded between the plate and the fluid in narrow radial passages of fluid downstream of the stagnation point for the small value of H/D. They turn out to be quasi-potential flow streams, along the target wall and facing the chevron apices, characterized by high convective velocities and nearly no turbulence. Increasing the distance to H/D = 6 yields a somewhat axisymmetric thermal behavior. Effects on Nusselt number values averaged over circular surfaces centered on the stagnation point and of variable radius on the target wall are highlighted.



12.
Study of dynamics of large-scale vortex structures in a sweeping jet entering a slot channel

M.V. Shestakov, D.M. Markovich
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk,Russia
Keywords: Inconel 617 nickel alloy, thermal diffusivity, thermal conductivity, laser flash method

Abstract >>
The experimental study was performed for a submerged turbulent jet that enters a slot channel with the height of h = 4 mm. The oscillating turbulent jet is generated by a fluidic oscillator with two feedback channels and the exit nozzle with the throat width of d = h . The working fluid is distilled water. The two-component velocity field was acquired using the PIV method with a high resolution up 50 5 kHz. The information was gained about the sweeping turbulent jet (both structure and dynamics) entering a slot channel for the Reynolds number in the range from 1500 to 8000. The jet flow to the slot channel generates large-scale 2D vortex structures. The travel frequency of those structures depends on the jet sweeping frequency produced by a fluidic oscillator. Comparison of the research result with available experimental data demonstrated that for a flow in a slot channel (with geometry h/d = 1) has a smaller angle of jet sweeping. For a higher Re number we observe a variation in distributions of average and pulsation characteristics of the sweeping jet as well as a decrease in the dimensionless jet sweeping frequency.



13.
Characteristics of the precessing vortex core in the isothermal model of a radial type burner

E.Yu. Gorelikov1,2, I.V. Litvinov1,2, D.A. Suslov1,2, M.A. Tsoy1, S.I. Shtork1
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: swirl flows, Particle Image Velocimetry (PIV), Proper Orthogonal Decomposition (POD)

Abstract >>
Experimental data on reconstruction of the spatial structure of a swirl jet in a burner model are presented. An isothermal case of free jet mixing with ambient air at various levels of flow swirl is considered. The high-swirl flows under study are accompanied by the collapse of the vortex core and intense coherent flow pulsations associated with large-scale vortex structures. Experimental data on distributions of axial and tangential velocities were obtained by Particle Image Velocimetry (PIV). The contribution of coherent flow fluctuations to turbulent transport is estimated based on the Proper Orthogonal Decomposition (POD). The frequency of periodic pressure pulsations was measured using acoustic sensors. The frequency of the precessing vortex core (PVC) and the corresponding velocity distributions were measured at a fixed Reynolds number (16500). A nonmonotonic dependence of the Strouhal number on the flow swirl was obtained. The spatial vortex structure was visualized under isothermal conditions. Using POD analysis, it was shown that with an increase in swirl, the precession radius and the pitch of the helical structure of the PVC increase.



14.
Kinematic structure of flows and the heat transfer in flat diffuser and confuser channels

R.R. Shakirov, I.A. Davletshin, N.I. Mikheev
Institute of Power Engineering and Advanced Technologies FRC “Kazan Scientific Center of RAS”, Kazan,Russia
Keywords: gradient flows, diffuser, confuser, flow structure, heat transfer

Abstract >>
Results of an experimental study of the kinematic structure of flow and the transfer of heat in gradient flows are reported. A field measurement method (SIV) was used to obtain profiles of velocities and turbulence characteristics in characteristic sections of diffuser and confuser channels. Based on the results of thermal measurements, the distributions of the heat-transfer coefficient on the wall of a flat diffuser/confuser were obtained in a wide range of regime parameters. The mechanisms of the formation of the transfer of heat in gradient flows are analyzed. It is shown that, in a diffuser channel, the transfer of heat on the wall as a whole depends on the flow parameters at the diffuser inlet. For a confuser channel, this relation can be determined using the local values of longitudinal flow velocity.



15.
An experimental study of the capillary elevation rate of water-alcohol mixtures on modified surfaces

M.V. Gorbachev1, M.S. Makarov1,2, A.I. Syuzaev1, V.I. Terekhov1,2
1Novosibirsk State Technical University, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: heat and mass transfer, boundary layer, modified surface, capillary-porous surface, water-alcohol mixture, evaporation

Abstract >>
The wetting dynamics of modified capillary-porous surfaces made of aluminum and titanium was experimentally studied at free-convective heat exchange with the environment. The influence of the concentration of ethyl alcohol and its initial temperature on the wetting front velocity has been established. The volume concentration of alcohol in the mixture varied from 0 to 95.5%. The characteristic modes of changes in the height of the liquid rise over capillary-porous surfaces over time have been expressed in the form of power dependences.



16.
Effect of channel height on performance of two-phase flow in miniand microchannels with a T-mixer

F.V. Ronshin1,2, Yu.A. Dementiev1,2, D.Yu. Kochkin1, E.A. Chinnov1,2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk,Russia
2Novosibirsk State Technical University, Novosibirsk,Russia
Keywords: two-phase flow, Т-mixer, slug flow, slug length

Abstract >>
The two-phase flow was experimentally studied in three horizontal channels of rectangular cross-section: 0.23×1 mm, 0.51×1 mm, and 1×1 mm. Distilled water was used as a liquid, and nitrogen was used as a gas. The paper considers in detail the features of two-phase flow formation. The effect of the rectangular channel height on the boundaries of two-phase flow regimes was investigated. It was found that the region of the bubble flow is hardly affected by the channel height; however, with a decrease in the latter, the region of the slug flow decreases significantly, while the region of the slug-annular flow expands. The characteristics of the slug flow have been studied in detail. The dependences of the length of gas slugs and liquid bridges on the reduced liquid velocity, the reduced gas velocity, and also the channel height have been studied. A comparison with known correlations is made and it is shown that they describe the experimental data in a narrow range of parameters, and as the height of the rectangular channel decreases, the data scatter increases.



17.
Active flow control in a model combustion chamber using additional gas injection method

A.D. Kundashkin1,2, E.V. Palkin1,2, M. Yu. Khrebtov1,2, R.I. Mullyadzhanov1,2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: large eddy method, precessing vortex core, flow control

Abstract >>
The large-eddy simulation method was applied to study of isothermal swirled gas flow in a model combustion chamber at Reynolds number Re = 15000. The study identified a coherent vortex structure: this is a precessing vortex core which contributes to pressure pulsations reaching a maximum inside a model front device. It is possible to suppress this coherent structure by gas injection in a site of highest pressure pulsations. The study covers three regimes with additional gas injection with the amplitude about 1 - 5 % of the superficial flow velocity. Analysis of instant, average and spectral characteristics revealed that the developed method of flow control is a tool for suppression of low-frequency oscillation by factor of two.



18.
Combustion of boron particles air suspension

A.P. Shpara, D.A. Yagodnikov, A.V. Sukhov
Bauman State Technical University, Moscow, Russia
Keywords: air suspension, nanoparticles, boron, flame propagation

Abstract >>
Mathematical simulation was applied to flame spreading and the flame front speed through the air suspension of boron particles as a function of pressure, excess oxidant ration and the particle size. Simulation accounts for a change in heat and mass transfer with a reduction of the particle size from micro-size to nano-scale. The model of flame front propagation through boron particle suspension in air (with account for molecular-kinetic mechanism of heat and mass transfer) allows analysis of the normal speed of flame propagation as a function of initial size of boron particles, oxidant excess ratio and pressure. The conditions were estimated and existence of extremes and flat zones was justified due to a change in heat and mass transfer regime change in a continuous medium while transition to the free-molecular flow regime.



19.
Thermal expansion of Hastelloy C276 in low-temperature area

Yu.M. Kozlovskii, S.V. Stankus
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: superalloy, Hastelloy C276, superconductivity, thermal coefficient of linear expansion, elongation, dilatometric method, low temperatures

Abstract >>
The experimental results obtained by the dilatometric method for thermal expansion of the Hastelloy C276 alloy in the temperature range of 100 - 370 K are presented. Temperature dependences of thermal properties have been obtained. The obtained results have been compared with the data for thermal expansion of superconducting tapes of the “Amperium” and “SuperOx” brands Keywords: