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We study the linear stability of a resting state for a generalization of the basic rheological Pokrovski-Vinogradov model for flows of solutions and melts of an incompressible viscoelastic polymeric medium to the nonisothermal case under the influence of magnetic field. We prove that the corresponding linearized problem describing magnetohydrodynamic flows of polymers in an infinite plane channel has the following property: for certain values of the conduction current which is given on the electrodes, i.e. on the channel boundaries, the problem has solutions whose amplitude grows exponentially (in the class of functions periodic along the channel). [ABSTRACT FROM AUTHOR]

A strong acoustic shock as a result of the outflow of a supersonic jet when discharging technical gases causes serious damage to ground facilities and the health of personnel. This leads to a significant decrease in the safety level of technical operation facilities. Therefore, the problem of reducing aerodynamic noise during supersonic jet outflow is urgent. The reducing possibility the aerodynamic noise of a supersonic jet is considered experimentally. The jet outflow from a long channel in which a pseudoshock is formed was considered. Two types nozzles were located at the end of the outflow channel. The first type nozzles with longitudinal slots and the second type are multichannel (multitube). In the experiment, the total noise level from the outflowing supersonic jet and the change in static pressure along the length of the outflow channel were measured. [ABSTRACT FROM AUTHOR]

The study is devoted to the evaluation of vibrational relaxation times in carbon dioxide using the kinetic theory methods. There are several relaxation channels in CO2, such as vibrational-translational energy transitions within modes and vibrational-vibrational exchanges between different modes. The theoretical expressions for the relaxation times of such processes are derived; they depend on the energy variation in a specific collision and cross sections of corresponding transitions. The first-order perturbation theory as well as two modifications of the forced harmonic oscillator (FHO) model are implemented for the transition probabilities. Relaxation times are evaluated in the temperature range 500–10000 K; it is shown that they are strongly affected by the cross section model. It is found that the FHO model provides good agreement with experimental data at low and moderate temperatures; at high temperatures, both models give non-monotonic trends for the relaxation times. The reasons of such behaviour are analysed. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the process of obtaining nanoscale powders under the action of an electron beam and subsequent condensation of vapors. The synthesis of powders can be significantly expanded to a larger range of the resulting compounds if the vapors react with the surrounding reagents and gases during the production process. [ABSTRACT FROM AUTHOR]

It is shown that the mechanism of the gas molecules transfer through the lipid bilayer can be connected with the kink-solitons. They are appeared in the lipid bilayer as a result of structural changes in biomembranes. The analytical model describing the behavior of kink-solitons in the finite hydrocarbon chain is presented. The kink-solitons are formed during the folding of the erythrocyte as it moves along the microcapillaries. The equation of the kink-soliton motion is derived. This equation is numerically solved. It is shown that kink-solitons can appear in both saturated and unsaturated alkyl chains. In unsaturated chains, the soliton is "smeared out," CH2−groups vibrate around C=C bonds with a significant amplitude, taking away part of the soliton's energy. The transport of gas molecules by kink-solitons in unsaturated chains is hindered in comparison with saturated hydrocarbon chains. When the mechanical stress field changes, a sharp change in membrane permeability occurs. [ABSTRACT FROM AUTHOR]

Results of numerical simulation of supersonic flow past a blunt fin mounted on a flat isothermal plate with a developing laminar boundary layer are presented. Generally, the case considered corresponds to the flow configuration used in the experimental and computational study by Tutty et al. [1], where the laminar air flow with the freestream Mach number of 6.7 past a blunt-fin body located at a distance of 145 mm from the plate leading edge is considered. In the present calculations, the diameter/thickness of blunt-fin (D) was gradually decreased from 2.5 mm to 1.0 mm (ReD = 1.25·104 to 5.0·103). Within the D-range from 2.5 mm to (approximately) 1.85 mm (ReD = 9.25·103), two stable stationary solutions corresponding to metastable flow states with different configurations of the upstream separation zone occupied by horseshoe-shaped vortices were predicted. The metastable solutions differ in the length of the separation zone, location of the main horseshoe vortex, and plate-surface heat flux distribution. One of the solutions predicted at D = 2.5 mm agrees well with the experimental data reported by Tutty et al. [1]. The bifurcation diagram showing the main horseshoe vortex center location versus the Reynolds number is presented. It shows, in particular, that one of the predicted solutions changes evolutionarily with increasing in ReD, whereas the second solution looks as an isolated solution at ReD > ReD,crit. ≈ 9.25·103. [ABSTRACT FROM AUTHOR]

The work is devoted to the experimental study of the effect of the B4C particles content on the microhardness and sliding wear behavior of a composite aluminum matrix coating produced by cold spray method. Using the technique of spraying mechanical powder mixtures, composite aluminum matrix coatings with boron carbide content of 3 – 17 vol.% were obtained. The coatings were examined by optical and scanning electron microscopy, X-ray diffraction analysis, and optical profilometry. The introduction of 17 vol.% boron carbide made it possible to increase the microhardness of the aluminum coating by approximately 1.5 times (up to 72.4 HV0.3). It was shown that the addition of carbide particles in the content range under consideration has practically no effect on the volume loss of the coating material during sliding wear. The results of measuring the coefficient of friction showed that with an increase in the test distance, the friction coefficient first decreases, while coatings with a higher content of the ceramic component correspond to lower friction coefficients. With a further increase in the test distance, the coefficient of friction increases, while the influence of the ceramic component on the coefficient is minimized. [ABSTRACT FROM AUTHOR]

Experimental studies of the model of the jet-driven Helmholtz oscillator, which is an axisymmetric channel of variable cross section, have been carried out. The model consisted of a cylindrical resonator chamber closed on the sides by two covers. The oscillator was excited by a stream of air flowing through the chamber between the inlet and outlet holes made in the side covers. The influence of the geometric dimensions of the chamber and the openings in the covers on the amplitude of pressure fluctuations was studied, and the optimal configuration of the channel was determined. Particular attention is paid to the study of the influence on the amplitude of pressure fluctuations of the shape and size of the nozzle - the hole in the front cover. The pressure drop across the nozzle, to calculate the speed of the jet at the entrance to the chamber, and the parameters of pressure fluctuations in the chamber, to plot the frequency response, were measured. Observations of the appearance of a jet-tone and the excitation of acoustic modes at the frequency of natural oscillations of the chamber-resonator with a smooth increase in the jet velocity were made. The absence of a relationship between the frequency of the jet-tone and the resonance frequency in the chamber was noted. Recommendations for the design of a jet-driven Helmholtz oscillator intended for use as a borehole transducer for stimulating an oil reservoir are presented. [ABSTRACT FROM AUTHOR]

A numerical simulation of a supersonic (M∞ = 7) flow around a cylinder with a front gas-permeable porous insert at a zero angle of attack was carried out using three-dimensional skeleton models of a highly porous cellular material made of non-intersecting hard spheres with a regular and chaotic arrangement of pores. A comparative analysis of these skeleton models with different spatial arrangement and pore size showed a weak influence of the structure of skeleton models on the resistance of a cylinder with a front gas-permeable insert. The computed data of the drag coefficient are compared with the results of tube experiments. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) control of welding defects in the process of cyclic loading of the stand was carried out. The stand is intended for life tests of the landing gear of a heavy aircraft. A certified microprocessor-based AE system SCAD-16.10 with "floating" selection thresholds was used. The AE signals emitted during the formation of defects that occur in the stand welds under the action of repeated cyclic tensile loads are registered. The location method with the calculation of their the difference in arrival times (DAT) based on the standard deviation (RMS) of the amplitude was used. The application was justified by analyzing the results of autocalibration of acoustic emission transducers (AET) which were installed on the top plate of the stand. Detection of developing design defects was carried out by analyzing changes in the parameters of AE signals that form active regions. The dependences of changes in the parameters of AE signals emitted by weld defects during their development in various areas of the stand were given. [ABSTRACT FROM AUTHOR]

The characteristics performance of the small quadcopter was measured in a wind tunnel. The effect of propellers on the lift and drag of the quadcopter frame has been found. The quadcopter descent stage was investigated numerically by the RANS approximation. The calculations allowed determining the interference between the from the propeller with the quadcopter frame element. A significant effect of the quadcopter frame on the propeller characteristics in the vortex ring state was found. [ABSTRACT FROM AUTHOR]

The study presents the results of numerical studies of mixing, ignition, and combustion of a jet of cold hydrogen along the bottom wall of the channel parallel to the supersonic free stream (M = 2) of an inert gas / vitiated air. The calculations were carried out using the commercial package ANSYS CFD Fluent based on the solution of unsteady Favre-averaged Navier-Stokes equations, supplemented by the k-ω SST turbulence model, models of turbulence-chemistry interaction (TCI), and several kinetic schemes of hydrogen combustion. Two detailed kinetics, including 16 and 37 reactions, are considered. The work used two models of turbulence-chemistry interaction: the vortex dissipation model (EDM) and its extended version eddy dissipation concept (EDC). This work aims to select the calculation method, the kinetic mechanism, and the TCI model, which provide good agreement with the experimental data. It is shown that, in the case of a non-reactive flow, the computational algorithm makes it possible to accurately predict the mixing parameters of a hydrogen jet and an external inert gas flow. For a reacting flow, the Kelvin-Helmholtz instability, which develops at the boundary of the combustion layer with the external flow, significantly affects the flow characteristics. [ABSTRACT FROM AUTHOR]

Aerodynamic wind tunnels the one of the widely used tools for aerophysics research. The wind-tunnel test technique allows the results of experiments transferred on full-scale objects. In view of the complexity of recording in supersonic flows, the numerical simulation affords opportunity to make more full description of process and to obtain distribution of gas-dynamic parameters. The purpose of the research is mathematical simulation of gas movement in internal volume of an impulse aerodynamic wind tunnel. For mathematical description of process Unsteady Reynolds averaged Navier-Stokes equations are used. The initial and boundary conditions are chosen according to aerodynamic experiments. By the numerical calculation a gas-dynamic parameters in steady supersonic flow on the edge of axisymmetric nozzle are obtained. Results of simulation corresponds with quasisteady flow regime in real aerodynamic tests. Obtained data can be used to solve a wide range of problems, theoretical and engineering analysis of experimental results. [ABSTRACT FROM AUTHOR]

The experimental study results of the mixing layer of subsonic jet exhausting from a convergent axisymmetric nozzle at a Mach number Ma = 0.85 are presented. The mixing layer thickness at the high-speed subsonic jet initial section is determined. The values and histograms of the flow velocity root-mean-square deviations at mixing layer different points are given. The applicability analysis of the panoramic laser PIV method to the structure study, average values and velocity pulsations characteristics in the mixing layer is carried out on the literature data basis on the level of pulsations in subsonic jet flows. [ABSTRACT FROM AUTHOR]

Investigation of supersonic flows in internal channels of various geometries is widely problem of aerospace. Nowadays, the ramjet engine with supersonic combustion is an advance engine for hypersonic aircrafts and space vehicles. The study of operating principle and mechanics of ramjet can be simplify to study of supersonic flow in a profiled internal duct simulates a section of a working path or fuel chamber. The aim of study is an experimental and computational study of supersonic flow in an internal axisymmetric internal channel with sudden expansion at case of oncoming flow velocity of M = 5 and M = 6. The proposed devices for pressure and temperature on wall of duct recording are described. The comparison of results of measurements in aerodynamic tests and corresponding numerical calculation is presented. Close agreement for experimental and numerical calculation obtained. Based on correlation of aerodynamic tests and simulation results verification of previously proposed approach for solve problem of flow around model in test section of aerodynamic wind tunnel presented. [ABSTRACT FROM AUTHOR]

The effect of particle condensation of cold gas flow on the formation of a secondary jet ("wake") behind supersonic nozzles is revealed in the studied range of the outflow initial parameters. The technique of gas jets photometry, which makes it possible to carry out linear measurements of the generated flows, is presented. An anomaly of the "wake" luminescence was discovered when the argon flow was excited by an electron beam. The wavelengths and the corresponding transitions Ar-I and Ar-II inherent in the "wake" glow were determined. The development of diagnostic methods for studying cluster jets is discussed. [ABSTRACT FROM AUTHOR]

In this work, the problem of axisymmetric gas flows through porous object with heterogeneous combustion sources under natural convection is considered. Heterogeneous combustion is a combustion which occurs when fuel and oxidizer are in different phases. The numerical approach based on combination of explicit and implicit finite-difference schemes is suggested for investigating these processes. It is shown that the location of ignition zone effects on process of propagating the combustion waves. For the axisymmetric case, as well as for the plane case, under natural convection vortex gas flows are observed near the combustion zone. This vortex flows effect on flow of oxidizer into the reaction zone. As in the plane case, the solid combustible component burns out completely, but the direction of the combustion wave propagation in the axisymmetric case can differ from the plane case. [ABSTRACT FROM AUTHOR]

The results of the calibration of the nozzle of a hot-shot wind tunnel with a new transonic insert for modeling the Mach number M = 4 are presented. This nozzle was used for preliminary tests of a hypersonic module with hydrogen combustion. It was found that hydrogen spontaneously ignites and its combustion leads to a fourfold increase in the static pressure in the model channel. Intensive pressure rising does not lead to disruption of the inflow in the air intake. [ABSTRACT FROM AUTHOR]

The paper provides a brief overview of recent computational studies of flow and heat transfer control by rotary oscillations of an infinite circular cylinder at a relatively broad set of imposed frequencies and amplitudes [1, 2]. A study for a previously unreachable high subcritical Reynolds number Re = 1.4 × 105 showed that the efficiency of this control method increases with Re concerning the issue of drag and lift reduction. High-frequency oscillations even lead to around 90 % reduction of the drag. However, the benefits for heat transfer enhancement is not that obvious as the bulk Nusselt number shows only small variations. At the same time its angular distribution around the cylinder becomes much more homogeneous due to oscillations which practically can prevent local overheats. [ABSTRACT FROM AUTHOR]

A series of computational experiments is discussed where a submerged round jet is subjected to different ways of active flow control to achieve the effect of jet splitting. The first method is to superimpose axial and helical excitations onto the velocity profile at the jet inlet. The second one consists of mechanical vibration of the jet inlet nozzle added to axial forcing. Both methods result in jet splitting at Reynolds numbers Re above 1000. At lower Re, the splitting is not guaranteed and requires pinpointing the optimal forcing frequencies and amplitudes to produce a meaningful effect. [ABSTRACT FROM AUTHOR]

The results of a theoretical study of the characteristics of a supersonic boundary layer on a flat plate at a Mach number under conditions of surface sublimation are presented. Naphtha-lene (C10H8) was chosen as the sublimation coating material. Early work showed that with an increase in the surface temperature, the mass consumption of evaporation of naphthalene also increases. This leads to a decrease in the wall temperature in comparison with the case of flow around a flat plate without sublimation. The large molecular weight of naphthalene in compar-ison with the molecular weight of air and a decrease in the surface temperature due to the evaporation of the wall material leads to an increase in the density of the binary mixture (air and sublimant vapor) near the wall. Such a change in the profiles of the boundary layer leads to a noticeable decrease in the local rates of growth of unstable perturbations [1]. The study of the effect of material sublimation from the surface on the flow in the boundary layer is associated with two main effects. The first of them consists in the effect of the injection of a foreign gas through surface, the second - with the expenditure of energy for the evapora-tion of the subluminous substance. [ABSTRACT FROM AUTHOR]

The unsteady problem of a shock wave / laminar boundary layer interaction development is considered for the case of sudden deflection the shock wave generator. The unsteady process of the separation zone growth and movement of the laminar-turbulent transition location was studied both numerically and experimentally. The position of the transition location was predicted in CFD by two approaches, namely by eN method based on linear stability theory (LST) [1], and by Menter model [2] κ-ω-γ-Reѳ in RANS simulation of the flow. [ABSTRACT FROM AUTHOR]

This work is devoted to the results of an experimental study of the laminar-turbulent transition in the boundary layer of the wing with a sweep angle of the leading edge of 72 degrees. Experiments were performed in a supersonic low noise wind tunnel T-325 ITAM SB RAS at Mach number 4. The measurements were carried out using a hot wire anemometer. Dependences of mass flow pulsations on Rex are obtained, according to which the position of the laminar-turbulent transition was obtained. Amplitude-frequency spectra were obtained and spectral analysis of disturbances was carried out. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of the influence of unit Reynolds number on the position of the laminar-turbulent transition in the supersonic boundary layer on a swept wing. The experiments were carried out in a T-325 supersonic wind tunnel of the Institute of Theoretical and Applied Mechanics named after S.A. Khristianovich on a wing model with a swept angle χ=72° at Mach number 2. That corresponds to a subsonic leading edge. The transition position was determined using a constant temperature hot wire anemometer. Comparison with previously obtained data for a wing model with 45 degree leading edge shown, that for the same flow parameters, the laminar-turbulent transition on the model of a wing with a subsonic leading edge occurs earlier than on a model of a wing with a supersonic leading edge. A unit Reynolds number has less impact on the transition position on a wing model with a subsonic leading edge, in contrast to a model with a supersonic leading edge. [ABSTRACT FROM AUTHOR]

The work is devoted to an experimental study of the development of natural disturbances in the modulated boundary layer of a swept wing model with a supersonic leading edge at Mach 2.5. Modulation of the mean floe in the boundary layer was created using rectangular stickers 80–85 µm in height. The hot-wire anemometer was used to measure the mean mass flow and pulsations. The spectra of natural disturbances of the boundary layer both in the case of a smooth surface and in the presence of periodic roughness are considered. [ABSTRACT FROM AUTHOR]

The results of an experimental study of the perturbation development created by pulsed glow discharge on the swept wing surface with periodic distributed roughness along the leading edge at Mach 2.5 are presented. This work continues research on this model at Mach 2. It was found that the mean flow modulation in the boundary layer of a swept wing with a sweep angle of 40 degrees leads to a change in the amplitude of artificial pulsations excited in the boundary layer by a disturbance source and to a strengthening of the oblique breakdown mechanism at a Mach number of 2.5. [ABSTRACT FROM AUTHOR]

The work is devoted to the experimental study of the development of mass flow and total temperature pulsations in the boundary layers of a flat plate and a swept wing at Mach numbers 2, 2.5 and 4. The experiments were carried out in a T-325 supersonic wind tunnel of the ITAM SB RAS. The pulsations were measured using a constant temperature hot-wire anemometer in the automatic scanning mode based on probe overheating. The analysis of the experimental data showed that for the experimental conditions at all stages of the laminar-turbulent transition of boundary layers, the mass flow and total temperature pulsations develop similarly, and the ratio of the pulsation levels practically does not change. [ABSTRACT FROM AUTHOR]

This work is devoted to the results of an experimental study of the impact of n-wave on heat transfer in a boundary layer of a flat plate at the Mach number 2. To generate N-wave into the flow, a roughness on the lower part of the nozzle of the test section of wind tunnel was used. As a result of the experiments, heat transfer data on the surface of a flat plate were obtained. A double longitudinal structure is shown in the form of a defect in temperature change caused by the interaction of two vortices with the surface of a flat plate model. The paper shows comparisons of the obtained distributions of the surface temperature difference in the cross section of the plate with measurements using a pitot tube and a constant temperature anemometer [ABSTRACT FROM AUTHOR]

An experimental measurement of the cross-correlation between free flow pulsations and disturbances of the boundary layer of a flat plate with a blunted leading edge at Mach 2 was performed. Measurements were carried out using a constant temperature hot-wire anemometer in the region of shock waves from a two-dimensional roughness installed on the surface of the test section, as well as in the region of vortices in the boundary layer. In the course of the experiment, the correlation coefficient distributions were obtained over cross-sections along the leading edge in the free flow and boundary layer. [ABSTRACT FROM AUTHOR]

The work is devoted to comparative analyzing the plume structure of gas-liquid mixture generated by nozzles of different performances. Pneumatic coaxial atomizers with outer mixing, differing 10 times in size, were investigated. Analysis of visualization results and droplet sizes data shows geometrical similarity of two-phase core of the jets of nozzles with different scales and their general resemblance regarding spray dispersion. A structure was found that makes it difficult to visualize the liquid jet in the vicinity of the nozzle exit, its nature is shown, and the mechanism of formation with an increase in gas pressure is investigated. [ABSTRACT FROM AUTHOR]

The paper studies the formation of a high-speed microjet flow which obtained with optical breakdown in the mode of radiation absorption behind the front of a laser supported driven detonation wave (LDW). Using numerical simulation of the interaction of a series of laser pulses with a subsonic argon jet, the conditions for obtaining a homogeneous high-speed jet and its characteristics are investigated. Ansys Fluent software is used for simulation. In contrast to the generally accepted approach, the calculation model takes into account not only the absorbed power, but also the breakdown plasma impulse in the region of radiation. [ABSTRACT FROM AUTHOR]

The main part of available data on boron particles combustion was obtained in flat-flame burner experiments. Boron particles were injected into flat-flame burner post-flame zone with a transporting jet of cold nitrogen; the combustion process of boron particles was registered with a number of optical methods. Systematization of ignition delay and combustion times of boron particles obtained in that type of experiment was done. Combustion times are represented in the form of particles linear combustion speeds. Combustion speed shows classic dependence on temperature, at low temperatures the reaction is temperature dependent and seems to be kinetically controlled, at high temperatures the reaction is diffusion controlled one. Most of the combustion data was obtained in wet environment. Kinetically controlled combustion depends on surrounding gas temperature, so the heat generation doesn't significantly heat the particle above the ambient temperature, such an effect is possible if heat release of the reaction on the surface of the particle is reduced. The boron oxide gasification process through formation on boric meta acid is studied. Equilibrium pressures are enough to provide observed in combustion experiments particles combustion rates. [ABSTRACT FROM AUTHOR]

Bluff bodies in a gas or liquid flow are a fairly common phenomenon, which is often found in both natural and technogenic processes. Various structural elements of aerospace transport systems, pipelines, gas turbines, heat exchangers, etc. in many cases can be considered, at least qualitatively, as a two-dimensional cylinder in a flow at some angle of attack. Depending on the specific situation, it may be necessary to suppress or intensify the process of vortex generation, increase or decrease the drag coefficient of the body, decrease or increase the level of noise produced by the body in a flow. The fulfillment of these tasks is impossible without knowledge of the mechanisms of formation of the flow under the current flow regimes. In the presented study, models of circular quasi-two-dimensional or finite cylinders are used as a bluff body model. To control the flow textile materials were used which were previously studied in other works of the co-authors [1]. These materials can cover the cylinders. The change of effective diameter of the cylinders then is around 1% and is considered insignificant when textile material is applied on cylinder. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of the thermal modes of a supersonic combustion chamber at Mach numbers at the channel inlet 3-4, operating on hydrogen. Model is made in the form of a rectangular channel with a combined flame holder with a backward-facing step and wedge-shaped injectors. The experiments were carried out in the mode of a connected pipeline under conditions close to flight ones. It was found that the maximum level of heat flux is reached in the region where the ignition of the mixture is initiated, and this value is achieved during the non-stationary ignition of the combustion chamber. The position of this region shifts upstream with a decrease in the Mach number, which depends on the change in the position of the separation region of shock waves interaction with the boundary layer. With an increase in the Mach number to 4, intense combustion does not occur due to the displacement of this region downstream into the diverging channel and is accompanied by a significant increase in the flow rate. The data obtained show that when developing systems for thermal protection of the combustion chamber, it is necessary to take into account the uneven distribution of heat fluxes along the combustor length in order to prevent local destruction of the walls and possible saving of the coolant resource. [ABSTRACT FROM AUTHOR]

The work is devoted to the numerical and experimental study of the problem, the construction of physical and technical models of the device for creation and registration of thermal marks. The problem was investigated by one-dimensional estimates, numerical modeling in two-dimensional and three-dimensional formulations with model verification on the created experimental setup. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of the interaction between a shock and the laminar boundary layer on a flat plate in motion in supersonic perfect-gas flow at Mach numbers M∞ = 2.3 and M∞ = 3 are considered. The shock is preassigned using the Rankine-Hugoniot boundary conditions, which corresponds to a shock wave produced by a wedge with a given semi-vertex angle in an inviscid gas flow. The simulation is based on the numerical solution of the time-dependent, two-dimensional Navier-Stokes equations by time marching to steady state. The numerical data are used to investigate the effect of the plate velocity of the separation flow structure and the basic laws governing the problem. It is shown that the motion of the plate downstream diminishes the separation zone length, whereas the opposite motion leads to its increase. [ABSTRACT FROM AUTHOR]

The paper is devoted to the investigation of the flow over flying wing surface. The main idea behind this work was to study the flow over full-sized unmanned aerial vehicle model for in-flight Reynolds numbers. Three-dimensional roughness element was placed on the leading edge as the generator of stationary disturbance. Using hot-wire anemometry the inner structure of this disturbance was shown. It consist of two counter-rotating disturbances different in size. This difference results from presence of cross-flow over the surface of the wing. [ABSTRACT FROM AUTHOR]

The goal of this paper was to study the viscosity of liquids and gases in nanochannels. The classical molecular dynamics method is used to simulate the viscosity of liquids in nanochannels. However, the transport coefficients are determined by the special fluctuation-dissipation theorems constructed by the authors on the basis of nonequilibrium statistical mechanics. These theorems generalize the well-known Green–Kubo formulas. The dependences of the viscosity coefficient of argon and benzene in channels made of copper and aluminum with square and circular cross-sections on the size of the channel are studied. The fluid viscosity in the channel can be either greater or less than its viscosity in the bulk. It is shown that the effective viscosity of the fluid can be controlled by changing the material of the channel walls. The decisive role in this effect played the depth of the well of the interaction potential of the wall atoms; with its increase, the effective viscosity of the liquid increases. To simulate the transport coefficients of rarefied gases in nanochannels, a method of stochastic molecular modeling has been developed. The walls are assumed to be solid, and the interaction of fluid molecules with them is described by specular, diffuse, or specular-diffuse reflection laws. A strong anisotropy of the viscosity of the gases in nanochannels, even with rather large sizes, has been established. The viscosity coefficients in different directions can differ by more than ten times. In this case the determining role plays the interaction of the gas molecules with the walls of the channel again. [ABSTRACT FROM AUTHOR]

During the operation of an oil producing well, it is very important to constantly monitor the flow rates of gas, oil, and water. This makes it possible to determine not only the current well operation mode, but also to optimize production in the future, and helps to form a complete picture of the processes in the reservoir. The cost of multiphase flowmeters capable of performing these functions is quite high, therefore they are installed only on a small number of wells. An alternative to direct multiphase measurement is the so-called virtual flow metering, where oil, gas and water flow rates are recovered from other known physical measurement. The paper presents a way when a single-phase flowmeter based on a Venturi pipe operates on the well, and the component composition is restored based on the well test data. [ABSTRACT FROM AUTHOR]

In a one-dimensional linear formulation, the problem of methane production from a deposit initially saturated with methane and its hydrate is considered. Three cases were considered, namely: methane production only due to pressure reduction at one reservoir boundary; pressure reduction at one reservoir boundary and heating from the opposite boundary; pressure reduction at one reservoir boundary and carbon dioxide injection at the opposite boundary (replacement method). A numerical study has shown that the most effective is a combination of the depression and replacement methods. With this combination the largest amount of methane is extracted in a shorter period, and a large amount of carbon dioxide is buried. [ABSTRACT FROM AUTHOR]

The temporal characteristics of the processes of deformation and disintegration of a freely falling drop of a low-viscosity liquid in an air accelerating flow are studied. The experiments were carried out under fast loading and in the regime of impulse-quasi-static loading of drops at moderate gradients of flow velocity. Experimental values of the interaction time and the induction time of the drop breakup are obtained. [ABSTRACT FROM AUTHOR]

During horizontal flight the propellers of quadcopter is working in oblique flow conditions. This case not studied enough for fixed pitch propellers especially at low Reynolds numbers, which are implemented on propellers of small quadcopters. The experimental investigation of characteristics of three-blade propeller for quadcopter in different conditions (including oblique blowing) was carried out. The effect of oblique flow mode on the dimensionless characteristics of the propeller was investigated. The unsteady component of the force generated by the propeller was estimated on the basis of numerical simulation. [ABSTRACT FROM AUTHOR]