Physics of Field, Neutral and Ionized Gases |
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Gaponov S. A., Terekhova N. M. The Oscillations, Branches from the Neutral Curve in a Supersonic Boundary Layer at M = 2 In the framework of the weakly nonlinear stability theory investigates soft and hard product of the periodic fluctuations in a supersonic boundary layer at Mach number M = 2. The model includes the effects of blooming (the product of the stationary secondary harmonics and the generation of perturbations of the double frequency). It is shown that in the framework of this model on the lower branch of the neutral curve appear region subcritical growth. This effect directly connected with the influence of compressibility. |
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Kornilov V. I., Boiko A. V., Kavun I. N., Popkov A. N. Air Blowing into Boundary Layer of a Flat Plate with Length-Dependent Permeability A generalized analysis of the results of numerical and experimental studies of air blowing into a turbulent boundary layer through finely perforated surface consisting of alternating permeable and impermeable sections of varying length providing a sudden change in the flow conditions at the boundaries of these sections is presented. The air blowing coefficient Cb determined by the mass flow rate per unit area of the active perforated sample varied in the range from 0 to 0.008. It is shown that as Cb grows, the maximum reduction in the mean surface skin-friction coefficient CF, which is the value through the permeable area of perforated sample, reaches about 65 %. When keeping the equal mass flow rate Q for all tested combinations, the mean skin-friction coefficient remains constant, independent of geometrical parameters of permeable and impermeable sections. Increasing the length of the last permeable section leads to the growth of relaxation region which is characterized by the reduced skin friction values on the impermeable part of the flat plate. |
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Mitryakov A. S., Litvinov I. V., Shtork S. I. Acquiring the Pulsation Characteristics of an Unsteady Vortex Flow with the Aid of Pressure Probes The special probes utilization together with measuring microphones allows to hold local measurements of pressure pulsations and to deform a flow structure marginally. Knowledge about a transfer function of the probe is required for the original signal reconstruction. This article presents the experimental technique of the probe transfer function obtainment. The theoretical assessment of the transfer function was carried out, using the model presented in the literature. Also the original signal reconstruction of pressure pulsations was carried out at the exit of the vortex tangential chamber. |
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Kozlov V. V., Grek G. R., Korobeinichev O. P., Litvinenko Yu. A., Shmakov A. G. Influence of Initial Conditions at the Micro Nozzle Exit on Hydrogen Diffusion Combustion The purpose of the given work will consist in an experimental study of influence of initial conditions at the micro nozzle exit on hydrogen diffusion combustion. It is shown, that the mean velocity profile and presence/absence of a heatcapacious material at the nozzle exit play an essential role on a flame structure and process of a round hydrogen microjet combustion. Velocity ranges of existence of a round hydrogen microjet diffusion combustion, flame separation and «bottleneck flame» region for a case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are found. Dependences of the «bottleneck flame» region size from a hydrogen microjet efflux velocity for case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are shown. Decrements of reduction of the «bottleneck flame» region size with growth of the hydrogen microjet efflux velocity for three situations of changes of initial conditions at the nozzle exit are determined. |
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Mezentseva N. N., Mezentsev I. V., Mukhin V. A. At Nucleate Boiling Heat Transfer Zeotropicmixtures a Horizontal Tubes Despite numerous empirical relationships, currently there is no sufficiently reliable and physically reasonable methodology for calculating the heat transfer coefficient at boiling the zeotropic binary blends. The main reason is the complexity of the boiling process mechanism. Zeotropic blends have the non-isothermal phase transition or the temperature glide. To perform the analysis, the results of experimental work on boiling the zeotropic blends inside the horizontal smooth tubes were processed. The studies were carried out with the horizontal smooth steel and copper tubes; the mass velocities were varied within 50–583 kg/m2*s; the specific heat flux was varied from 1 to 45 kW/m2. The experimental data, corresponding to the region of nucleate boiling, were compared with the calculated dependencies. The dependences corresponding to pool boiling were also analyzed. It was proposed to determine the heat transfer coefficient by Gogonin’s dependence (2006); this coincides well with the experimental data. This dependence takes into account the effect of wall thermal properties and its roughness on heat transfer. Moreover, it was found out that, in contrast to pool boiling, for the forced vapor-liquid flow in pipes at nucleate boiling, the diffusion processes are not important. |
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Solid-state and semiconductor physics, physics of nanostructures |
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Partizan G., Mansurov B. Z., Medyanova B. S., Koshanova À. B., Mansurova M. E., Aliyev B. À., Xin Jiang. Structure and Morphology of Carbon Nanofibers Synthesized on Cu Nanopowders This article presents the results of experiments on the synthesis of carbon nanofibers by thermal
chemical vapor deposition using copper nanopowders obtained by electric explosion of wire as catalysts. |
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Educational and Methodical Provision of Teaching of Physics |
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Gerasimov V. V., Grigorieva E. V., Knyazev B. À., Choporova Yu. Yu. Application of Systems with Total Internal Reflection at Novosibirsk Free Electron Laser for Spectroscopy in the Terahertz Range Attenuated total reflection (ATR) spectroscopy is widely used in the visible and infrared spectral ranges. Progress in the development of laboratory scale monochromatic sources of terahertz radiation, such as quantum cascade lasers, suggests that in the near future this kind of spectrometers will be widely spread in the terahertz range. For this reason, the development of ATR based methods and devices is highly relevant. In this paper, we discuss the features of the use of ATR spectroscopy in the terahertz range, and describe some of the optical systems, designed for experiments at the Novosibirsk free electron laser (NovoFEL). We show that in the terahertz range the ATR spectroscopy has a number of significant advantages over the absorption spectroscopy. As an example, we are discussing the possibility of using terahertz polarimetry to develop a method for early diagnosis of cancer via the detection of left-handed to right-handed polysaccharide enantiomers ratio. Spectra of selected polysaccharides were recorded with a standard Fourier spectrometer using developed by us an ATR unit. The possibility of studying the polarization characteristics of polysaccharides in aqueous solutions using spectrally selective polarimeter with the NovoFEL as a tunable radiation source was demonstrated. |
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