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Vestnik NSU. Series: Physics. 2016. V11, i 1 |
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Physics of Field, Neutral and Ionized Gases |
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Gaponov S. A., Smorodsky B. V. Laminar Supersonic Boundary Layer of the Binary Gas Mixture Theoretical investigation of the properties of a compressible binary-mixture boundary-layer in the framework of local self-similar boundary-layer equations. We have considered the problem, when the foreign gas of various molecular weights – lighter and heavier than air – has been injected into the flat-plate boundary-layer through the permeable model surface. Computations of the binarymixture velocity, density and temperature profiles as well as foreign gas concentration in such boundary layers at different Mach numbers have been performed. It has been found that increase of a foreign gas injection leads to a monotonous decrease of the skin friction and heat transfer coefficients. It has been established that at free stream Mach number M?2 action of a heavy gas injection from the model surface into the boundary layer is similar to the action of the model cooling. This injection increases the density of the mixture near the wall. As a result, the profiles of the supersonic boundary layer are modified in such a way that the boundary-layer linear stability should be increased with injection of a foreign gas with high molecular weight. This in turn should lead to a shift in position of the laminar-turbulent transition downstream. |
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Dryasov A. D., Yermolaev Yu. G., Kosinov A. D., Semionov N. V., Semionov A. N. Influence of Vortex Disturbances on Laminar-Turbulent Transition in Supersonic Boundary Layer on a Swept Wing at M = 2.5 Experimental investigations of the receptivity of a supersonic boundary layer on a swept wing to the vortex perturbations were made at Mach 2.5. A symmetrical wing model with a 45? sweep angle and a 3-percent-thick circular-arc airfoil was used in experiments. The investigation of the vortex disturbances structure generated by a wire was done. It has been shown that the level of disturbances in the free flow increases with increasing wire diameter. The positions of the laminarturbulent transition at different diameters of wire were determined and data of the disturbances development in the model boundary layer were obtained. It was found that an increase in the intensity of vortex disturbances in the free flow leads to an earlier transition. Receptivity coefficients were determined. |
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Golubev M. P., Shmakov A. S. Application of Elastic Layers to Register Pressure Field on the Model Surface in Supersonic Flow The work presents the results of application of panoramic interferential technique which is based
on elastic layers (sensors) usage to obtain pressure distribution on the flat plate having sharp leading
edge. Experiments were done in supersonic wind tunnel at Mach number M = 4. Sensitivity and
response time are shown to be enough to register pressure pulsation against standing and traveling
sensor surface waves. Applying high-frequency image acquiring is demonstrated to make possible
to distinguish at visualization images high-speed disturbances propagating in the boundary layer |
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Goldfeld Ì. A., Zakharova Yu. V., Starov À. V., Timofeev Ê. Yu. Slotted Channel as a Gasdynamical Source of Ignition and Flame Stabilization in the Supersonic Combustion Chamber The original scheme of flame stabilization in the channel at close to cocurrent fuel supply for the fuel combustion at a high supersonic speed has been designed. Such solution provides high temperature of a stream in a zone of fuel-air mixture formation. Computational and experimental investigations of self-ignition and combustion of hydrogen were carried out in the model of combustor chamber with slotted channel (gasdynamical source of ignition) at Mach numbers 3.7 and 5.8 at the entrance. Tests have been performed in hot-shot wind tunnel IT-302M of ITAM SB RAS in a mode of the attached pipe. Numerical study has been performed on the basis of solving the full averaged Navier-Stokes equations, supplemented k-? SST turbulence model. Configuration of the slotted channel has been designed with two variants of exit nozzle: with and without geometrical throat. It has been established that at the channel entrance two vortexes with high temperature have been appeared. Temperature has been keeping high in the channel with geometrical throat and at blocking of the slotted channel without throat. It was found that uniform subsonic stream in the channel with geometrical throat has been realized. The stream in the slotted channel without geometrical throat keeps supersonic but Mach number was lower than in the main channel. The structure of the flow at the slotted channel exit is significantly differs for this both cases. |
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Yusupov R. R., Shtork S. I., Alekseenko S. V. Study of Strongly Swirling Gas-Liquid Flows in a Hydrodynamic Vortex Chamber The work is devoted to experimental study of one-phase and two-phase swirling flow in a horizontal vortex chamber with a tangential swirler. Special attention is paid to an emergence of unsteady vortex structures. Formation of a precessing vortex core (PVC) in the nozzle has been detected in the case of one-phase flow. Linear dependence of the PVC precession frequency and quadratic dependence of the full pressure drop in the vortex chamber on the fluid flow rate were confirmed experimentally. In the case of two-phase flow a high-speed visualization allowed to reveal the presence of the secondary vortex structures in cylindrical region behind the zone of sudden expansion. Adding a gas phase into the flow leads to a sharp decline of the precession frequency and full pressure drop decrease in the vortex chamber. The frequency smoothly decreases with further increase of gas content and pressure drop changes insignificantly: slightly increases or decreases depending on the water flow rate. At the same time there is a coherent change of the flow’s integral characteristics at changing the flow rates of liquid and gas. |
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Kuibin P. A., Litvinov I. V., Sonin V. I., Ustimenko A. S., Shtork S. I. Modelling Inlet Flow in Draft Tube for Different Regimes of Hydroturbine Operation One of the main sources of powerful pressure pulsations in the fluid flow parts of the hydroturbine at partial load or overload operation regimes is the precessing vortex rope forming due to high residual swirl of the flow downstream the hydroturbine wheel. Numerical simulation and experiments have been performed in order to study the influence of inlet flow conditions in the draft tube on level of the flow pulsations. Numerical calculations have shown that it is possible to reproduce velocity distributions at the draft tube inlet corresponding to different operation regimes of the real hydroturbines using a combination of two blade grids – rotor and stator. Experimental verification of numerical calculations was performed using an aerodynamic test rig and method of 3-d printing for fabrication of the blade grids and draft tube model. Velocity field measurements at entrance of the draft tube conical part making use of an laser-Doppler anemometer and level of the pressure pulsations using acoustic probes have allowed to define correlation between the velocity distribution type and amplitude-frequency characteristics of the flow pulsations which generated by the precessing rope. |
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Kozulin I. A., Kuznetsov V. V., Bartkus G. V. Experimental Investigation of Explosive Boiling Organic Liquids by Measuring the Laser Intensity Reflected on Microbubbles In this paper the experimental study was made for explosive boiling of liquids under pulsed heating. Experimentally obtained patterns for explosive boiling of organic liquids (ethylene glycol, octane) with the help of optical method measuring the laser intensity reflected from the microheater surface. A multi-layered thin film heater was used in experiments as microheater manufactured by Hewlett Packard technology, with size 100 x 110 mcm. The data of dynamics boiling shown that high heat flux density provide the conditions for the phase explosion whose properties was studied experimentally, including the history of surface vapor covering, nucleation time and the lifetime of the main bubble. |
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Bartkus G. V., Kuznetsov V. V. Experimental Investigation of Detailed Structure of Gas- Liquid Flow in Rectangular Microchannel The detailed structure of upward gas-liquid flow of water and nitrogen in a vertical microchannel with a rectangular cross-section 420 x 280 mcm was experimentally investigated. The experiments were conducted using the methods of high-speed video and laser-induced fluorescence. In a wide range of flow rates the characteristic regimes of the gas-liquid flow were defined, velocity of elongated bubbles and the local thickness of the liquid film were measured. The dependence of the local film thickness on the capillary number was determined and it was found that the Taylor Law for rectangular channel is not fully implemented due to the deformation of the interface and the contraction of the liquid into the corners of the channel by capillary force. |
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Solid-State and Semiconductor Physics, Physics of Nanostructures |
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Tkachenko O. A., Tkachenko V. A. Sensitivity to Disorder of Graphene-Like Lattices of Quantum Dots and Antidots in Two-Dimensional Electron Gas We compare three-dimensional electrostatics of semiconductor structures with graphene-like lattices of quantum dots and antidots formed in the plane of the two dimensional electron gas. With lattice constant fixed, the shape of the potential may be tuned so that both lattices have minband spectrum where the second Dirac feature is pronounced and not overlaid by the other states. We show that the lattice of quantum dots is more sensitive to fabrication imperfections, because sources of the disorder are located directly above the electronic channels. Thus the lattices of antidots should be preferred semiconductor artificial graphene candidates. |
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Utkin D. E., Shklyaev A. A., Dultsev F. N., Latyshev A. V. Formation of Two-Dimensional Photonic Crystals with Cavities Arrays in Silicon Specific aspects of finely focused electron beam interaction with the PMMA-950K resist for the fabrication of closely spaced holes having inhomogeneous spatial distributions are studied. The technological parameters for the creation of two-dimensional photonic crystals with microcavities (missing holes) arrays, which allow obtaining the lateral sizes of the structure within the accuracy better than 2 %, in silicon using electron-beam lithography are determined. Such holes fabrication accuracy is thought to be sufficient to study the interference effects of cavity array radiation in twodimensional photonic crystals. |
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Sitnikov S. V., Kosolobov S. S., Latyshev A. V. Formation Two Dimensional Negative Islands at High Rate Cooling of Ultra-Flat Surface Si(111) In situ ultrahigh vacuum reflection electron and ex situ atomic force microscopy have been applied to investigate morphology transformations of the ultra-flat stepped Si(111) surface with wide (20–50 mcm in diameter) singular terraces during sublimation and quenching from elevated temperatures. The formation of two dimensional negative (vacancy) islands has been observed on the wide terraces after the quenching from temperatures above 1 200°C. The increasing of the critical terrace size for the two-dimensional negative island nucleation has been explained by the changing of the atomic mechanism of mass transport on silicon surface. |
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Chemical, Biological and Medical Physics |
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Strizhakov R. K., Kuzhelev A. A., Tormyshev V. M., Bagryanskaya E. G. EPR Spectroscopy of Trityl Radicals: Specificities of Hyperfine Interaction of an Unpaired Electron with 13C Nuclei The constants of hyperfine coupling between an unpaired electron and natural occurrence 13C
have been registered for the representative series of trityl radicals. The analysis of hyperfine añ constants |
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High-Energy and Accelerator Physics, Physics of High-Temperature Plasma |
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Arzhannikov A. V., Beklemishev A. D. An Electro-Jet Rocket Engine with Big Thrust at Helical Corrugated Magnetic Field A fundamentally new electro-jet rocket engine having a big thrust with a high specific impulse is described in this paper. The acceleration mechanism of magnetized plasma along the axis of a cylindrical chamber with a helical corrugated magnetic field is put in the basis of such engine. The plasma acceleration is achieved during its drift motion by applying a radial electric field. The analytical description of the plasma motion process gives a visual representation of how the diamagnetic forces provide the process of the continuous acceleration of plasma ions along the axis of the helical corrugated magnetic field. As the result of this process, the accelerated plasma stream flows through the expanding cross section of a magnetic nozzle and the thrust of the rocket engine is created. Estimated calculations showed the ability of the new electro-jet rocket engine to achieve the big trust (in the range 10^2–10^4 Newton) with the high specific impulse (from the level 3·10^4 to 10^3 seconds, respectively) at a reasonable efficiency. This set of parameters is fundamentally unattainable for another jet engines operating on the basis of other physical mechanisms. |
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