Vestnik NSU. Series: Physics. 2016. V11, i 2

Physics of Field, Neutral and Ionized Gases

Aniskin V. М., Rudyak V. Ya. Experimental Studying Nanofluid Thermal Transfer in Microchannel

In paper new setup for studying the thermal transfer of nanofluid in the steel micro-channel with inner diameter 358 microns is described. Setup testing carried out by means of known experimental data about thermal transport of the water. Then the data about the thermal tranfer coefficient of the water based nanofluids with silicon dioxide nanoparticle with average size 25 nm are discussed. It was shown that nanofluids have the thermal transfer coefficient much more than that of base liquid. The enhancement of the thermal transfer coefficient of one-percent nanofluid is about 60 %. This enhancement grows with increasing of the nanoparticles volume fraction and flow rate of the nanofluid.

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Pavlenko A. N., Surtaev A. S., Volodin O. A., Serdyukov V. S. Distribution of Liquid Nitrogen at the Film Flow in the Single Elements of the Structured Packing

Experimental results on the parameters of the film flow of cryogenic liquid over the surface of single elements of the structured packing consisting of two corrugated plates are presented. The effect of microtexture and its direction relative to the direction of gravity on liquid distribution along the packing at different irrigation degrees is shown based on the comparison with experimental data. Experimental results on the degree of liquid flowing through the contact points in the packing with plates are presented relative to the irrigation degree. It is shown that microtexture and its direction have a significant influence on redistribution of the local liquid flow, flowing on the structured surface of complex geometry, along the packing.

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Pavlenko A. N., Surtaev A. S., Volodin O. A., Serdyukov V. S. About Influence of Inclination Angle of Ribs on the Distribution of Liquid Nitrogen at a Film Flow in a Single Structured
Packing Elements

Experimental results on the parameters of the film flow of cryogenic liquid over the surface of single elements of the structured packing consisting of two corrugated plates are presented. The effect of inclination angle of large ribs on liquid distribution along the packing at different irrigation degrees is shown based on the comparison with experimental data. It is shown that changing the angle of the ribs leads to a substantial redistribution of local flow rate of the flowing liquid across the width of the package. The character of this redistribution significantly depends on the degree of irrigation.

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Yatskikh A. A., Kolosov G. L., Kosinov A. D., Yermolaev Yu. G., Panina A. V., Semionov N. V. Experimental Study of Effects of Couple Weak Waves on Laminar-Turbulent Transition on Attachment Line of Swept Cylinder

Experimental data of investigation of the influence of outer couple weak shock waves on the laminar-turbulent transition on attachment line of swept cylinder in supersonic flow are presented. The couple of waves were generated by a two-dimensional roughness on the wall of the test section of supersonic tunnel. It was found that the laminar-turbulent transition on the attachment line of sliding cylinder followed by abrupt perturbation growth. In case of the great distance between falling of the waves on attachment line and the point of measurement the impact on transition was not observed. In case of the short distance between falling of the waves on attachment line and the point of measurement the laminar-turbulent transition was observed at lower unit Reynolds numbers.

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Lysenko V. I., Smorodsky B. V., Yermolaev Yu. G., Kosinov A. D., Semionov N. V. Joint Influence of Surface Roughness and Permeability on Stability and Transition of Mach = 2 Boundary Layer

Joint theoretical and experimental investigation of the influence of surface permeability and roughness on stability and laminar-turbulent transition of the supersonic flat-plate boundary layer at free-stream Mach number M = 2 have been performed. Good quantitative agreement of experimental data obtained with artificially generated disturbances performed on models with various porous inserts and calculations based on the linear stability theory has been achieved. At research of the joint effect of the model surface permeability and roughness on the boundary layer stability and transition, it is shown that, as a certain (critical) roughness value is reached, with the rough and porous coating thickness increase, the boundary layer stability diminishes and the laminar-turbulent transition is displaced toward the model leading edge.

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Vankova O. S., Goldfeld M. A., Fedorova N. N. Control of Processes of Ignition and Combustion Stabilization in the Supersonic Combustion Chamber

In the paper, results of mathematical modeling of a flow in the supersonic combustion chamber are presented, which have been performed under the conditions of burning initiation by means of an electronic bunch of high energy on the basis of the offered ignition model. Calculations are carried out on the basis of the Reynolds averaged Navier – Stokes equations supplemented by the k–w SST
turbulence model and detailed chemistry kinetics. As a result of numerical modeling, it has been shown that in a frame of the offered model it is possible to predict the ignition of mixture at low stagnation temperatures. The numerical results confirm the experimental data. It is shown that the choice of the optimum scheme of stabilization and the stabilizer geometry allows one to get the flame propagation over all the channel and to provide the stability of combustion even at high flow Mach numbers. The offered mathematical model has allowed defining the conditions of ignition.

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Shmakov A. G., Grek G. R., Kozlov V. V., Litvinenko Yu. A., Korobeinichev O. P. Diffusion Combustion of the Round Microjet Mixture of Hydrogen with Metane, Helium and Nitrogen

The purpose of the given work will consist in an experimental studies of the diffusion combustion features of the hydrogen round microjet mixtures with the metane, helium and nitrogen. It is found, that the mechanism and characteristics of a microjet and a flame evolution at diffusion combustion of the hydrogen mixture with the metane, helium or nitrogen are connected with the «bottleneck » flame area formation, as well as in a situation of a pure hydrogen microjet diffusion combustion. It is revealed, that process of diffusion combustion of a hydrogen / metane mixture in a round microjet is accompanied by stage-by-stage stages of a turbulent flame detachment at preservation of combustion in the «bottleneck» flame area, and, at last extinction of microjet combustion that correlates with combustion process of a similar microjet of pure hydrogen. It is found, that all above-listed stages of a hydrogen / metane mixture combustion are realized in a range considerably smaller speeds of a microjet (200-500 m/sec), than in a similar situation of a pure hydrogen microjet combustion (600-800 m/sec). It is shown, that at diffusion combustion of a mixture of hydrogen with metane or helium or nitrogen in a round microjet for stabilization of combustion with growth of a microjet speed it is necessary to increase a portion of hydrogen (or to reduce a portion of an impurity) in a mixture of gases.

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Chemical, Biological and Medical Physics

Papulovskiy E. S., Shubin A. A., Lapina O. B. Theoretical Modeling of the Structure of Surface Niobium Sites Based on Solid-State 93Nb NMR

In this work niobium oxide clusters on the surface of Al2O3 are modeled using DFT calculations. 93Nb NMR parameters of modeled clusters were computed with the GIPAW method. The niobia system under consideration represents high niobium loading on the surface of the support. The niobium atoms are highly coordinated and linked to the other niobia polyhedra by one or two bonds. The most of the niobium oxide particles has a coordination number of six. The correlations found between 93Nb NMR parameters and coordination environment are discussed.

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Educational and Methodical Provision of Teaching of Physics

Zakharov M. I. Diffraction of a Plane Monochromatic Wave at the Circular Aperture and Circular Disk

In the framework of the scalar theory of diffraction of normally incident plane monochromatic wave, the intensity distribution of the diffraction field along the axis of an annular hole was found. As particular cases, the diffraction at an opaque circular disk of radius R >> l (l is the wavelength) and at a circular aperture in an opaque screen was considered. Accounting for the vector nature of the field of electromagnetic waves led to more correct results, including at large angles of diffraction, i.e. at sufficiently small distances from the screen (smaller and of order R), where the scalar theory, as it is known, not applicable.

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Brief Reports

Litvinenko М. V., Litvinenko Yu. A., Vikhorev V. V. Visualization of Vortex Structures in the Near Field of the Round Jet Formed in Curved Channel by PIV-Method

The results of experimental investigation of the round jet with Dean vortices (Red = 4 000, De = 1 673) using Particle Image Velocimetry are presented. The measurements were performed with synchronization the phase of acoustic signal and a laser pulse. Instant picture of vorticity field wz and vector velocity field for the U- and V-components of the jet cross-actions show Dean vortices near the output of the channel in the low velocity gradient field and Kelvin – Helmholtz vortices in the high-velocity gradient field. The presence of Dean vortices distorts two-dimensional vortex ring, which gets an ?-shaped form, at that the « head» of ?-vortex outpaces its «legs», as it is in a higher velocity area.

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