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Thermophysics and Aeromechanics

2011 year, number 1

Interferometric technique for measurement of droplet diameter

A.V. Bilsky1, YU.A. Lozhkin1, D.M. Markovich2
1 Kutateladze Institute of Thermophysics SB RAS
2 Kutateladze Institute of Thermophysics SB RAS; Novosibirsk State University
Keywords: droplet diameter, interferometer, laser, gas-droplet flow, IPI
Pages: 1-12

Abstract >>
The paper considers the optical contact-free method of droplet diameter sizing in the flow cross-section utilizing light interference on a droplet. Distribution of light scattered by a particle was analyzed for different configurations of the measurement system using the Mie theory and approximation of geometrical optics. Basic measurement errors and dynamic range were determined. Possibility of measurements with camera mounting at the angle of 90º to the plane of a laser sheet is shown; this simplifies setup calibration and evens characteristics over the image field. The procedure of measurement system calibration and a set of algorithms for data processing are suggested. The suggested approaches were applied for measurement of characteristics of the gas-droplet jet.

Hydrodynamics, heat and mass exchange in sprayer sprinkling chambers

M.I. Shilyaev, E.M. Khromova, A.V. Grigoriev, A.V. Tumashova
Tomsk State University of Civil Engineering
Keywords: liquid droplets, heat and mass exchange, moisture content, steam and gas flow, sprayer sprinkling chambers
Pages: 13-24

Abstract >>
A two-dimensional physical and mathematical model of the motion and heat and mass exchange of a steam and gas mixture with liquid droplets of variable mass in sprayer sprinkling chambers at high moisture contents is formulated by using the concepts of interpenetrating continua with different velocities and temperatures. An analysis of this model is carried out.

Investigation of acoustic waves propagation and flow in nanodispersed medium

S.P. Bardakhanov, V.I. Lysenko, V.V. Obanin, D.YU. Trufanov
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
Keywords: nanodisperse powder, flow, acoustic waves
Pages: 25-30

Abstract >>
Propagation of acoustic waves in nanodisperse powders and powder flow under the influence of acoustic vibrations have been investigated in the horizontal tube with the use of visualization and hot-wire anemometer methods.

Boiling-up of liquid argon at high superheatings under the impact of weak ultrasonic fields

V.G. Baidakov, A.M. Kaverin, V.N. Andbaeva
Institute of Thermophysics UB RAS
Keywords: acoustic cavitation, nucleation, superheat, boiling-up, argon
Pages: 31-36

Abstract >>
The technique of lifetime measurement for metastable liquid and continuous depressurization technique were applied for study of kinetics of spontaneous cavitation in superheated liquid argon under impact of weak ultrasonic fields. It was demonstrated that acoustic cavitation may occur through the mechanism of homogeneous generation of vapor phase or through swinging of vapor bubbles generated by high-energy particles and/or other kinds of initiative factors. The thresholds of acoustic cavitation are described by the theory of homogeneous nucleation.

Local characteristics of the upward bubbly flow in an annular channel

O.N. Kashinsky, A.S. Kurdyumov, P.D. Lobanov
Kutateladze Institute of Thermophysics SB RAS
Keywords: bubbly flow, annular channel, void fraction, wall shear stress, electrochemical method
Pages: 37-41

Abstract >>
Results of experimental investigation of the bubbly gas-liquid flow in a vertical annular channel are presented. The average and pulsation shear stresses and distributions of local void fraction were measured by the electrochemical method on both channel walls. It is shown that with a rise of gas flow rate ratio the value of wall shear stress increases significantly, and this effect becomes higher at a decrease in superficial liquid velocity. A presence of the gas phase effects significantly shear stress on the inner wall. Relative intensity of shear stress pulsations increases similarly on both channel walls.

Development and experimental investigation of small-sized thermo-electric generator with diffusion combustion

R.V. Fursenko, S.S. Minaev, D.V. Chusov
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
Keywords: small-sized energy conversion devices, diffusion combustion, thermoelectricity
Pages: 43-50

Abstract >>
Laboratory samples of small-sized energy converters based on thermo-electric method of heat conversion which source is diffusion microflame are presented in the work. Processes of combustion, energy conversion, and cooling in the proposed systems have been experimentally studied. Relatively high efficiency of the studied systems (energy-conversion 0.8 % at generated electric power of 130 mW) complying with the current world level for such devices is shown. The advantages of the proposed power generators are absence of forced-cooling system and catalysts, assemblage simplicity and usage of available materials and components. On the basis of investigation results, possible ways of further improvement of test samples have been determined with the view of energy conversion efficiency increase.

The effect of scratch technique on the thermal-product value of temperature sensors

H.A. Mohammed, H. Salleh, M.Z. Yusoff
College of Engineering, Universiti Tenaga Nasional
Keywords: temperature sensor, thermal product, junction surface, shock tube
Pages: 51-64

Abstract >>
The effect of different scratch techniques, mainly abrasive papers and scalpel blades used to form the junctions of temperature sensors, on the thermal-product value of these sensors, was examined. A dynamic calibration procedure of scratched sensors in a shock tube facility which allows easy evaluation of their thermal-product value is outlined. The thermal product of a particular sensor was found to be dependent on the flow Mach number, junction scratch technique, junction location, and also on the enthalpy conditions. It was shown that using different scratch techniques normally results in different thermal-product values of sensors. The experimental procedure used in the present study has yielded practical data on characteristics of scratched temperature sensors; these data can be used in accurate measurement of transient heat transfer under hypersonic flow conditions.

Flow fluctuation measurement in the flow-through path of continuous electric-discharge СО2в€’laser contour

V.N. Zinoviev, V.A. Lebiga, A.YU. Pak, YU.V. Afonin, A.M. Orishich
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
Keywords: gas laser, air gap, velocity fluctuations, hot-wire anemometer
Pages: 65-71

Abstract >>
We have experimentally proved the applicability of hot-wire anemometer method to measure fluctuations at low pressures and gas flow rates when medium is no longer considered as continuous. Use of individual calibration at working conditions serves to apply standard technique for determination of sensitivity coefficients of hot-wire probes. Additional investigations are necessary to take into account influence of Knudsen number and, possibly, other parameters in heat transfer law presented as criterial dependence of Nusselt number on Reynolds number. Hot-wire measurement of mean velocity distribution and their fluctuations in the flow-through path of electric-discharge CO2 laser have been performed. The level of velocity fluctuations in the vicinity of anode is high that is caused by the zone of interacting flows from the ventilators rotating in opposite directions forming in the symmetry plane. Placing of the damping screen between the ventilator and air gap allows decreasing fluctuations intensity to the acceptable level. It has been ascertained that the vortex shedding with high intensity of fluctuations which influence is noticeable in significant part of air gap is formed in the wake behind the streamlined cathode. However, pulsation level in the proper gap does not exceed permissible values.

Investigation of turbulence models for computation of swirling flows

A.V. Sentyabov1, A.A. Gavrilov2, A.A. Dekterev1
1 Krasnoyarsk Department of the Institute of Thermophysics SB RAS; SiberianFederal University
2 Krasnoyarsk Department of the Institute of Thermophysics SB RAS,
Keywords: swirling flows, eddy precession, turbulence models, method of modeling of detached eddies
Pages: 73-85

Abstract >>
Different turbulence models were studied in application to calculation of swirling flows. The differential models of turbulent viscosity considering streamline curvature and the method of detached eddy simulation were used. Weakly and strongly swirling flows were considered at the example of concentrated vortex in a tube, swirling flow in a diffuser, and vortex breakdown through an abrupt expansion. The RANS models with correction to flow swirling represented well the experimental data for the weakly swirling flows. In case of strongly swirling flows, it was more correct to use the method of detached eddy simulation.

Design of supersonic three-dimensional inlets using two-dimensional isentropic compression flow

YU.P. Goonko, I.I. Mazhul
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS,
Keywords: three-dimensional (3D) inlets, two-dimensional (2D) flows, gasdynamic design, supersonic velocities, design and off-design flow regimes
Pages: 87-100

Abstract >>
The design of supersonic three-dimensional inlets using the V-shaped body forming a two-dimensional flow including an initial oblique shock wave and a subsequent isentropic compression wave is considered. Such a flow appears attractive for inlets design due to a possibility of obtaining high compression levels of external flow over the inlet ramp with small losses of the total pressure. Numerical computations of the flows around the designed configurations were carried out in design and off-design regimes using Euler code. The flow structure was identified, the aerodynamic characteristics of the inlets were determined. The investigation covers the range of supersonic speeds corresponding to the freestream Mach numbers М = 1.8−2.5.

Transient growth of stationary flow perturbations at laminar boundary-layer separation

A.V. Boiko1, A.V. Dovgal1, A.M. Sorokin2
1 Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
2 Khristianovich Institute of Theoretical and Applied Mechanics SB RAS; Novosibirsk State University
Keywords: hydrodynamic instability, flow separation, transient growth, aerodynamic experiment
Pages: 101-106

Abstract >>
In a subsonic wind tunnel, laminar boundary-layer separation at a backward-facing step on a flat plate modulated by stationary flow perturbations was examined. The stationary disturbances were introduced into the flow by controlled roughness elements spaced on the model surface close to the separation line. Through a comparison of obtained data with results gained in previous studies of other periodic roughness systems, some trends in the generation of stationary disturbances subject to transient growth in separation region were revealed.

Mathematical simulation of conjugate turbulent natural convection in an enclosure with local heat source

M.A. Sheremet
Tomsk State University
Keywords: conjugate heat transfer, natural convection, turbulence, local heat source, rectangular region, numerical modelling
Pages: 107-121

Abstract >>
A numerical analysis of turbulent regimes of the natural convection in a closed rectangular region with heat-conducting walls of finite thickness was carried out in the presence of a locally concentrated heat source under the conditions of the radiative-convective heat exchange with the ambient medium on one of the external boundaries. The mathematical model was constructed on the basis of the Reynolds equations in dimensionless variables stream function − vorticity vector − temperature. Special attention was paid to the investigation of the influence of the Grashof number 10^8<Gr<10^10, of the unsteadiness factor , and the thermal conductivity ratio a2,1=5.7*10^-4, 6.8*10^-5 on both the local and integral characteristics of the problem.

Structure parameters and structure sensitive properties of Sn0.739Pb0.261 melt

V.M. Sklyarchuk1, YU.A. Plevachuk1, A.S. Yakimovich1, I.I. Shtablavy1, S.V. Stankus2, R.A. Khairulin2
1 Ivan Franko Lviv National University
2 Kutateladze Institute of Thermophysics SB RAS,
Keywords: structure factor, interdiffusion, viscosity, Sn?Pb eutectic, melt
Pages: 123-128

Abstract >>
Structure, interdiffusion, and dynamic viscosity of eutectic Sn−Pb melt have been experimentally investigated in a wide temperature range. On the basis of the obtained data on the position and form of the first maximum of the structure factor in the framework of the hard sphere model, values of sphere packing index and sphere diameter have been determined for the melt at 470 and 570 K. Correlations resulting from the model of hard spheres served to calculate coefficients of dynamic viscosity and interdiffusion of liquid alloy. Besides, temperature dependence of dynamic viscosity has been calculated with the use of thermodynamic approximation of Kozlov ⎯ Romanov ⎯ Petrov. Calculated values of the properties have been compared with experimental data.

Effect of hydrothermal conductivity on thermal resistance of porous materials

S.S. Efimov, E.G. Starostin, N.I. Tappyrova
Institute of Physical-Technical Problems of the North SB RAS
Keywords: porous material, hydrothermal conductivity, moisture, thermal resistance, thermogradient coefficient
Pages: 129-134

Abstract >>
Results of experimental study for dependency of thermogradient coefficient on moisture in porous material have been presented. These experimental data were used for estimating the effect of hydrothermal conductivity on heat transfer.

Modelling of thermal conductivity in hybrid composites made from binding matrix, with orthogonal reinforcement with tubes and with disperse-hardened hollow inclusions

A.P. Yankovsky
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS
Keywords: thermal conductivity, composites, hollow fibers, disperse inclusions, generalization of Fourier's law, Stephan ? Boltzmann law
Pages: 135-150

Abstract >>
The models were developed for thermal conductivity of a binding medium reinforced with tubes and with disperse-hardened hollow inclusions; the models have versions with/without consideration of relaxation times of materials making the phases of composition. For a limiting case, when tubes degenerate into solid fibers, we compared calculated values for efficient thermal conductivity coefficients for the case of single-direction and crisscross reinforced composites with corresponding experimental values. A satisfactory agreement between theory and experiment takes place.

Thermal conductivity of refrigerant 507A in gaseous state

O.I. Verba
Kutateladze Institute of Thermophysics SB RAS
Keywords: thermal conductivity, refrigerant, R 507A, method of coaxial cylinders
Pages: 151-154

Abstract >>
Thermal conductivity of refrigerant 507А in gaseous state has been measured with a stationary method of coaxial cylinders in the temperatures range of 315 - 425 K and pressures 0.105 - 1.855 MPa. Estimated values of temperature, pressure, and thermal conductivity measurement errors are, respectively, ± 0.05 K, ± 3.75 kPa and ± 1.5 − 2.5 %. Approximation dependence for thermal conductivity in the whole studied temperature and pressure range has been obtained. Results have been compared with available literature data.

80th Anniversary of Anatoly M. Kharitonov

Editorial board
Siberian Branch of the RAS
Pages: 155-156

Abstract >>
16 January, 2011  was the 80th anniversary of the Doctor of Technical Sciences, the Honored Worker of Russian Science, winner of the Award of the Council of Ministers of the USSR, Professor Anatoly Mikhailovich Kharitonov.

75th Anniversary of Vyacheslav N. Yarygin

Editorial board
Siberian Branch of the RAS
Pages: 157-158

Abstract >>
30 December, 2010  was the 75th anniversary of the Doctor of Technical Sciences, the Honored Worker of Russian Science, winner of the USSR State and of the Award of the Council of Ministers of the USSR, Professor Vladimir Kostantinovich Baev.