Publishing House SB RAS:

Publishing House SB RAS:

Address of the Publishing House SB RAS:
Morskoy pr. 2, 630090 Novosibirsk, Russia

Advanced Search

Thermophysics and Aeromechanics

2015 year, number 6

Investigation of a wake decay behind a circular disk in a hydro channel at high Reynolds numbers

I.V. Naumov1, I.V. Litvinov1, R.F. Mikkelsen2, and V.L. Okulov1,2
1 Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2 Danish Technical University, Lyngby, Denmark
Keywords: wake flow past a body, free-stream flow turbulence level, velocity deficit, similarity of velocity profiles, laser Doppler anemometry, PIV
Pages: 657665

Abstract >>
LDA and PIV techniques were used to study the decay of an axisymmetrical turbulent wake originated downstream an immobile disk in a water flume for Reynolds numbers Re = 1.5-2.4×105. Data were compared with experiments performed with a set of thermo-anemometers behind a disk in a wind tunnel at lower Reynolds numbers (Re = 1.3-2.6×104).
Observations for a new range of Reynolds number confirmed that the velocity distribution in the disk wake keeps self-similarity. The decay of a wake by the power law -2/3 in the presented experiments remains until the maximum deficit of velocity becomes comparable with the turbulent pulsation level in the free-stream (less than 2 %).

DOI: 10.1134/S0869864315060013

Gas dynamics of a supersonic radial jet. Part I

V.F. Kosarev, S.V. Klinkov, V.N. Zaikovskii, and S.G. Kundasev
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: supersonic radial jet, cold spraying, pressure profile
Pages: 667676

Abstract >>
The gas dynamics of a supersonic radial jet was studied under conditions close to cold spraying. The jet visualization was performed for exhaustion into submerged space with atmospheric pressure and jet impingement to a target. For the cases of swirled and unswirled supersonic radial jets, the pressure profiles measured by a Pitot tube were taken for different distances from the nozzle outlet and for different widths of supersonic part δex = 0.52 mm and for prechamber pressure in the range p0 = 12.5 MPa.

DOI: 10.1134/S0869864315060025

Turbulent mixing of small-obstacle-induced perturbations with the separated shear layer behind a backward-facing step

A.Yu. Dyachenko, Ya.I. Smulsky, V.I. Terekhov, and N.I. Yarygina
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: backward-facing step, turbulent separated flow, mini turbulators, thermographic visualization, heat transfer, pressure coefficients, instability
Pages: 677688

Abstract >>
In the present paper, we consider one of the most efficient and simple methods to additionally intensify the exchange processes and heat transfer in the separated flow behind a backward-facing step. The method uses small obstacles installed upstream the step; such obstacle act as turbulators smaller in size than the main obstacle. As the turbulators, solid mini ribs, comb ribbings, and wall-detached mini ribs were used. Intensification of the turbulent mixing process behind the main obstacle occurs due to the introduction of small-obstacle-induced 2D and 3D perturbations into the separated shear layer behind the step. Results of a detailed experimental study of the distributions of pressure and heat transfer for different heights of the small intensifier and its positions with respect to the step are reported. The influence of intensifier shape on the thermal and dynamic characteristics of the flow has been analyzed. The distributions of pressure and heat-transfer coefficients were used to evaluate the effectiveness of the various mini ob-stacles and the limits of their action on the drag and heat transfer.

DOI: 10.1134/S0869864315060037

Separated flow behind a backward-facing step under a stationary temperature disturbance

A.V. Boiko1,2, A.V. Dovgal1, and A.M. Sorokin1,3
1 Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2 Tyumen State Oil-and-Gas University, Tyumen, Russia
3 Novosibirsk State University, Novosibirsk, Russia
Keywords: laminar flow separation, separation control, hydrodynamic instability, temperature perturbation
Pages: 689700

Abstract >>
The flow in the separation region of laminar boundary layer behind a rectangular backward-facing step has been experimentally examined under temperature non-uniformity of the flow. The data were obtained in a subsonic wind tunnel at Reynolds numbers M << 1. The temperature disturbance was generated using a system of Peltier elements provided on the model surface upstream of the separation line. The effect of heating/cooling of the wall on the mean and fluctuating flow components was evaluated using hot-wire measurements. The experimental data were supplemented with calculations of linear-stability characteristics of model velocity profiles in the separated boundary layer. As a result, the response of the separated flow to a stationary thermal perturbation was revealed.

DOI: 10.1134/S0869864315060049

Experimental investigation of the temperature field in the gas-liquid two-layer system

E.Ya. Gatapova1, R.A. Filipenko1,2, Yu.V Lyulin1, I.A. Graur3, I.V. Marchuk1,2, and O.A. Kabov1,4
1 Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2 Novosibirsk State University, Novosibirsk, Russia
3 Aix-Marseille Universite, Marseille, France
4 Tomsk Polytechnic University, Tomsk, Russia
Keywords: microthermocouple, liquid-gas interface, temperature jump, evaporation
Pages: 701706

Abstract >>
Results of an experimental investigation of the temperature field across the liquid-gas two-layer system are presented. The liquid layer is locally heated from the bottom substrate, and the intensive liquid evaporation is observed. A technique for measuring the temperature profile across the liquid and gas layers (including their interface) is developed. To do these measurements, the microthermocouple is moved across the layers with the help of precision micropositioner with a step of 1 m. The temperature jump at the liquid-gas interface is measured, and its value increases with the temperature increase. Detailed information on the temperature field near the interface is obtained by using the precise thermocouple displacement with a small step.

DOI: 10.1134/S0869864315060050

Enhancement of transient heat transfer at boiling on a plate surface with low thermoconductive coatings

A.N. Tsoi and A.N. Pavlenko
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: film boiling, nucleate boiling, transient heat transfer, liquid nitrogen, low thermoconducting coating, heat transfer coefficient, cooling rate
Pages: 707712

Abstract >>
An experimental study of transient cooling in liquid nitrogen of strongly overheated copper plate coated with a low thermoconductive coating with thickness δ from 0.09 to 0.67 mm was performed. It is shown that the low thermoconductive coating has a significant effect on the character of temperature curves and total time of plate cooling. It was revealed that the most significant decrease in the time of plate cooling by the factor of 2.6 is achieved for the thickness of the low thermoconducting layer of 0.09 mm as compared to the case without coating.

DOI: 10.1134/S0869864315060062

Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

V.V. Kuznetsov and A.S. Shamirzaev
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: heat transfer in boiling, upward flow, plate-fin heat exchanger, refrigerant R-21
Pages: 713721

Abstract >>
The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capil-lary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

DOI: 10.1134/S0869864315060074

Evaluation of optimal thermal-hydraulic characteristics ratio in microchannel heat exchangers

A.B. Garyaev, O.E. Prun, and A.V. Klimenko
National Research University Moscow Power Engineering Institute, Moscow, Russia
Keywords: microchannels, microchannel heat exchangers, optimization of thermal and hydraulic characteristics, mi-crochannel heat exchanger efficiency
Pages: 723732

Abstract >>

In this paper, an analytical method of microchannel heat exchanger characteristics optimization is described. An objective function that combines thermal-hydraulic and constructive parameters of a heat-exchanger such as number, diameter, and length of channels, was developed. Limitations on its application were determined. Influence of these parameters on the functions value was analyzed. It is demonstrated that for each fixed amount of microchannels and its length, an optimal channel diameter exists. Formulas for optimal ratio of length, diameter, and number of microchannels evaluation were derived. It was shown that the maximum value of the objective function corresponds to a thin heat exchange matrix that consists of a large number of short channels with small diameter.

DOI: 10.1134/S0869864315060086

The pulsating laminar flow in a rectangular channel

E.P. Valueva and M.S. Purdin
National Research University Moscow Power Engineering Institute, Moscow, Russia
Keywords: hydrodynamics, pulsation laminar flow, numerical simulation, microfluidics
Pages: 733744

Abstract >>
The finite difference method is used to solve the task of the developed pulsating laminar flow in a rectangular channel. The optimum of the difference scheme parameters was determined. Data on the amplitude and phase of the longitudinal velocity oscillations, the hydraulic and friction drag coefficients, the shear stress on the wall have been obtained. Using the dimensionless value of the frequency pulsations two characteristic regimes the quasi-steady-state regime and the high-frequency regime have been identified. In the quasi-steady-state regime, the values of all hydrodynamic quantities at each instant of time correspond to the velocity value averaged over the cross section at a given moment of time. It is shown that in the high-frequency regime, the dependences on the dimensionless oscillation frequency of oscillating components of hydrodynamic quantities are identical for rectilinear channels with a different cross-sectional form (round pipe, flat and a rectangular channels). The effect of the aspect ratio of the rectangular channel sides channel on the pulsating flow dynamics has been analyzed.

DOI: 10.1134/S0869864315060098

Correlation algorithm for computing the velocity fields in microchannel flows with high resolution

M.N. Karchevskiy1,2, M.P. Tokarev1, A.A. Yagodnitsyna1,2, and  L.A. Kozinkin1,2
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Novosibirsk State University, Novosibirsk, Russia
Keywords: Particle Image Velocimetry, Single Pixel Resolution, micro-PIV, velocity field, velocity fluctuations, micro-channel
Pages: 745754

Abstract >>
A cross-correlation algorithm, which enables the obtaining of the velocity field in the flow with a spatial resolution up to a single pixel per vector, has been realized in the work. It gives new information about the structure of microflows as well as increases considerably the accuracy of the measurement of the flow velocity field. In addition, the realized algorithm renders information about the velocity fluctuations in the flow structure. The algorithm was tested on synthetic data at a different number of test images the velocity distribution on which was specified by the Siemens star. The experimental validation was done on the data provided within the international project 4th International PIV Challenge. Besides, a detailed comparison with the Particle Image Velocimetry algorithm, which was realized previously, was carried out.

DOI: 10.1134/S0869864315060104

Regenerative heat exchanger with a periodic change in the airflow direction for room ventilation

M.I. Nizovtsev, V.Yu. Borodulin, and  V.N. Letushko
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: energy efficient ventilation, air-to-air heat exchanger, regenerative packing
Pages: 755765

Abstract >>
This paper presents the results of experimental research of heat transfer in air-to-air regenerative heat exchanger with periodic change of flow direction. The temperatures of the airflow and the material of regenerative packing in different sections have been obtained. The temperature efficiency of the heat exchanger has been determined at dif-ferent flow rates. The developed mathematical model of the regenerative heat exchanger is described. It is shown that the model fairly well describes the experimental results. Based on numerical studies the dependence of thermal efficiency of the heat exchanger on the airflow rate is determined. It is shown that changing the ratio of the oppositely directed flow rates, it is possible to regulate the temperature of the air flowing into the room. The possibility of using the model for optimizing the operational and design parameters of heat exchanger is demonstrated.

DOI: 10.1134/S086986431506011

On the determination of the position of laminar-turbulent transition in boundary layer by optical methods

D.A. Bountin, Yu.V. Gromyko, A.A. Maslov, P.A. Polivanov, and A.A. Sidorenko
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: optical flow diagnostics methods, laminar-turbulent transition, schlieren visualization, heat flux
Pages: 767770

Abstract >>
As a rule, aerodynamic studies at hypersonic flow velocities are carried out in short-duration wind-tunnel facilities. For such facilities, optical diagnostic methods are most preferable. In the present study, we give for the first time a comparison of two methods for determining the end of laminar-turbulent transition: from the distribution of heat fluxes and from schlieren visualization data for the boundary-layer flow. Parametric data on the position of the tran-sition are obtained. These data can be used in the future as reference ones while calibrating semi-empirical calculation models for the transition.

DOI: 10.1134/S0869864315060128

Experimental investigation of liquid drop evaporation on a heated solid surface

A.A. Semenov1,2, D.V. Feoktistov3, D.V. Zaitsev2, G.V. Kuznetsov3, and O.A. Kabov1,2,3
Novosibirsk State University, Novosibirsk, Russia
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Tomsk Polytechnic University, Tomsk, Russia
Keywords: evaporation, contact angle, three-phase contact line
Pages: 771774

Abstract >>
Evaporation of a water drop was studied experimentally at a temperature difference between the solid surface and surrounding atmosphere from 30 to 60 C. The studies were performed on the substrates with micro- and nanocoatings with different wettability. The features of evaporation were studied for the pinned, partially pinned, and depinned three-phase contact line (solid-liquid-gas interface). It is shown that with a decrease in the water drop volume, the specific evaporation rate (mass flow per unit of surface area) increases, particularly at the last stage of evaporation.

DOI: 10.1134/S086986431506013X

Investigation of thermal plasma generator of technological function

A.S. Anshakov1,2, E.K. Urbakh 1, V.S. Cherednichenko2,3, M.G. Kuzmin3, and A.E. Urbakh1
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Novosibirsk State Technical University, Novosibirsk, Russia
JSC Sibelectroterm, Novosibirsk, Russia
Keywords: plasmatorch, arc discharge, current-voltage arc characteristics, heat losses, electrode lifetime
Pages: 775778

Abstract >>
Experimental results on energy characteristics of electric-arc plasma generator for heating technical nitrogen with the power of up to 500 kW are presented. The features of arc discharge glow, thermal efficiency, and service life of the electrodes were determined under the regime of melting the metallurgical raw material in the test plasma electric furnace.

DOI: 10.1134/S0869864315060141

75th Anniversary of Vasiliy M. Fomin

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia
Pages: 779780

Abstract >>
On November 5, 2015 Vasiliy M. Fomin, the Full member of the Russian Academy of Sciences and noted researcher, working on mathematical simulation of the problems of continuum mechanics and mechanical engineering, became 75 years of age.

DOI: 10.1134/S086986431506015