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SIBERIAN JOURNAL OF PHYSICS. Scientific Journal. 2017. V12, i 2 |
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Physics of a Fluid, Neutral and Ionized Gases |
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Nazarov D. V., Pavlenko A. M., Zanin B. Yu. Visualization of the Flow around the Ekranoplan Model The flow around the ekranoplan model was experimentally investigated in subsonic wind tunnel
at low Reynolds numbers with a low level of flow turbulence. The method of carbon-oil visualization
of surface streamlines was used in the experiments to obtain the flow pattern on the surface of
the model. Different areas of separation and vortex structures on the fuselage and wing were discovered. |
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Reshetova A. I., Poplavskaya T. V. Numerical Investigation of the Evolution of Disturbances on a Flat Plate in a Hypersonic Flow of a Mixture of Vibrationally Excited Gases The problem of the evolution of disturbances in a hypersonic viscous shock layer on a plate in the flow of a mixture of vibrationally excited carbon dioxide and nitrogen is considered by solving of the Navier – Stokes equations. Two channels of vibrational relaxation of CO2 molecules in collisions with CO2 and in collisions with N2 were taken into account by using a two-temperature model of relaxation flows in modeling the thermal nonequilibrium. The data on the dynamics of the evolution of disturbances on f flat plate in a wide range of determining parameters (attack angle A = 5 - 20°, concentration of CO2 in mixture, braking temperature T0 = 2000 - 4000 K) are presented in this paper. |
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Kosinov A. D., Golubev M. P., Pavlov Al. A. On Determination of the Mechanism of Mach Wave / Bow-Shock Interaction The work presents the results of investigation of interaction of outer couple weak shock waves with a bow shock produced by a triangle plate at Mach number M = 2. The couple of waves were generated by a two-dimensional roughness on the wall of the test section of supersonic tunnel. Hotwire measurements showed generated to free flow perturbations to correspond to N-wave. Optical visualization was done applying schlieren technique and interferometric method using adaptive visualizing transparencies based on absorption saturation. Qualitative coincidence of hotwire and interference data was obtained. Inclination angle of weak waves passed through the bow shock was observed to change. |
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Shmakov A. G., Grek G. R., Kozlov V. V., Kozlov G. V., Litvinenko Yu. À. Experimental Study of the Diffusion Combustion of a High-Speed Round Hydrogen Microjet. Part 1. Attached Flame, Subsonic Flow Scenario of subsonic diffusion combustion of a round hydrogen microjet is presented in this work. Stabilization of process of the laminar hydrogen microjet flow and diffusion combustion in region of the «flame bottleneck» is found. The reason of this phenomenon is connected with existence of the toroidal vortex which is promoting as intensification of mixing process of hydrogen with air and at the same time stabilizing a laminar flow of the extended microjet and its laminar diffusion combustion. It is shown that subsonic diffusion combustion of a round hydrogen microjet of is connected with availability of the «flame bottleneck» region in a wide range of a hydrogen consumption, or microjet velocity efflux close to transonic velocity. It is found that heating of a thick-walled micronozzle from «flame bottleneck» region in case of its big thermal capacity has significant effect on characteristics of development of the hydrogen microjet combustion and leads to choked nozzle. It is revealed that the spatial size of the «flame bottleneck» region with growth of a hydrogen consumption at first sharply decreases, and then gradually increases simultaneously with change of the «flame bottleneck» region shape while combustion in this region doesn't stop. |
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Kozlov V. V., Grek G. R., Litvinenko M. V., Litvinenko Yu. À., Shmakov A. G. Experimental Study of the Diffusion Combustion of a High-Speed Round Hydrogen Microjet. Part 2. Lifted Flame, Supersonic Flow Scenario of supersonic diffusion combustion of a round hydrogen microjet is presented in this work. The main features of supersonic diffusion combustion of a hydrogen round microjet are shown: disappearance of a «bottleneck flame» region, lifted flame from the nozzle exit and existence of supersonic «shock cells» in the lifted turbulent flame. The main reason for this scenario of diffusion combustion connected with a temperature factor is found i.e. with existence of thin-walled micronozzles with a small thermal capacity and a possibility of their quenching that doesn't give the chance to exist of the «bottleneck flame» region at big speeds of a microjet efflux. It is shown that with growth of temperature of a micronozzle heating from the «bottleneck flame» region at the same speed of a microjet efflux growth of its spatial size (l/d) is found. |
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Trilis A. V. Modeling of Transverse Detonation Waves in a Flat-Radial Annular Channel Acoustic properties of two regions of gases with different temperatures arising at the initial stage of evolution of transverse detonation waves in annular channel were examined. Mechanics of acoustic vibrations and waves are studied using both numeric and analytical and methods. Rotating circumferential waves at boundary surface of two gases with different temperatures were discovered and rotation velocities of these waves were determined. |
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Mironov S. G., Poplavskaya T. V., Kirilovskiy S. V. Investigation of the Air Flow in Heated Highly Porous Cellular Materials Measurements of air filtration rate through the highly porous cellular materials in the presence of heating a porous material were carried out. A new measurement technique was developed and data of the dependence of the filtration rate of the temperature of air passing through the porous material were obtained with different pore size and in wide range Reynolds number. The experimental data were compared with the results of numerical modeling of the airflow in the porous samples, based on skeletal model of the cellular-porous material. |
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Pavlenko A. N., Surtaev A. S., Volodin O. A., Serdyukov V. S. The Features of the Film Flow of Liquid Nitrogen over the Corrugated Plates with Combined Microtexture Experimental results on hydrodynamics of cryogenic liquid film flow over the surface of the single elements of the structured packing are presented. Based on the comparison of experimental data, the effect of microtexture form, diameter of the holes on the zones of liquid film spreading over a corrugated surface is shown for different values of the film Reynolds number. It is shown that the presence of combined microtexture (with the periodic change in its direction at the height of the sheet) leads to a better spreading of the liquid nitrogen film on the surface of the corrugated perforated sheet. Analysis of experimental data shows that the presence of the periodic zones with vertical orientation of the microchannels on the sheets with the combined microtexture provides the greater flow of liquid through the holes compared to the sheet having the horizontal direction of microtexture. The use of smaller holes, while maintaining the same total area occupied by holes, at the small degree of irrigation also leads to increasing size of the wetting zones on the sheet with combined microtexture. |
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Zavjalov A. P., Syzrantsev V. V., Zobov K. V., Tananaev I. G., Trufanov D. Yu., Bardakhanov S. P. Physical Base of Associated Layer Model Applied to Nanofluid Viscosity Description The paper presents the mechanistic model for explaining the experimental data on the nanofluids viscosity, which is based on the assumption about the layer of liquid on the nanoparticles surface, which associates with them the mechanical solid inclusions. This allows us to supplement the Batchelor formula with the parameter whose selection allows us to fit it with the experimental data. Independent methods of estimating the associated layer thickness from experimental data are also presented. Its value is ~ 10 nm, which is in agreement with the papers on the flows of fluids in thin hydrophilic quartz capillaries. The physical cause of this layer formation is supposed in the structuring action of the nanoparticles surface, which is expressed in the ordering of the water molecules dipole momentum directions in the near-surface layers. This leads to the difference in the optical properties of the adjacent to the particles water layers and the bulk water, which allows one to explain the fundamentally different results of measuring the dimensions of nanoparticles in a liquid by various optical methods, both among themselves and in comparison with the nanoparticles specific surface. The methods of direct influence on the particles size distribution are also proposed which can allow us to verify the assumption (on which the considered associated layer mechanistic model essentially relies) of the possibility to group different nanopowders and introducing into the group a general parameterized function of the particle size distribution. |
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Bardakhanov S. P., D. Trufanov Yu., Zavjalov A. P. New Type of Medium – Gases with High Concentration of Nanoparticles The article gives an overview of the works, the results of which indicate the necessity of posing the problem of describing new types of continuous media containing large concentrations of nanoscale particles. The importance of this problem is underlined for understanding modern technological processes in which nanopowders of various nature are formed, and in the form of nanoparticles whose concentration reaches significant values is increasingly used. Examples of practically important flows of powder materials are considered. The concept of a new continuous medium with a high concentration of nanoparticles is proposed, and the «hot-anemometric method» is applied. |
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Popov V. N. Modeling of the Alloying Substances Distribution in the Melt during Pulsed Induction Heating of the Substrate Under study is the applicability of the high-frequency electromagnetic field impulse for metal heating and melting with a view to its subsequent alloying. The processes of heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt are considered with the aid the proposed mathematical model. The substrate surface is covered with a layer of alloying substances. The distribution of the electromagnetic energy in the metal is described by empirical formulas. Melting and solidification of the metal is considered at the Stephan’s approximation. The flow in the liquid is described by the Navier – Stokes equations in the Boussinesq approximation. According to the results of numerical experiments, the flow structure in the melt and distribution of the alloying substances was evaluated versus the characteristics of induction heating. |
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Gubanov D. A., Zapryagaev V. I. Multimode Pulsations in the Axisymmetric Cavern at Supersonic Flow Experimental study results of flow structure and pressure pulsation spectral characteristics of axisymmetric cavern at supersonic flow with Mach number 2 is presented. Multimode pulsation existence is observed. Different modes dominate in different time moments. Maximum of one mode amplitude correspond to minimum value of another. Mode tuning nature is incidental. Time of one mode existence is much more than one of mode oscillation period. It is determine that pulsation mode exist in the form of toroidal and helical disturbances. Numerical calculation results qualitative reproduce multimode fluctuation and corresponded to experimental data. |
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Educational and Methodical Provision of Teaching of Physics |
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Shterk G. V., Kvon R. I., Nartova A. V. Tuneling Spectroscopy Study of the Local Conductivity Features of the Solid State Surface The procedure of the scanning tunneling spectroscopy experiments on the base of air multimicroscope SMM2000T is developed. Highly oriented pyrolytic graphite single crystal was chosen as model sample. Proposed approach allows investigation of the local nonuniformity of the surface properties. The statistical confirmed difference of volt-ampere curves recorded over pyrolytic graphite terrace and steps determined by the structure features is shown. |
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Brief Reports |
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Aktershev Yu. S., Vasichev S. S., Veremeenko V. F. Precision Four-Quadrant Current Source VCH-500-12R for Superconducting Solenoids A precision controllable bidirectional current source 0-500A for superconducting solenoids used in particle physics experiments has been proposed. This article discusses the operation principle of the designed device including a 40-kHz voltage conversion with subsequent synchronous rectification and an approach to energy recuperation from large inductive loads. It also presents some circuit designs aimed at reducing switching losses and increasing the overall efficiency. Current instability for 8 hours of continuous operation is no more than 0.01 % of the normal current. |
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