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This paper presents a model of working processes in the combustion chambers of micro gas turbine engines, taking into account turbulence, combustion, the detailed mechanism of chemical reactions, radiation, swirling flow, and the presence of oil in the fuel mixture. The results of calculations and experiments with the combustion chamber of the JetCat P100-RX engine are presented. Estimates of the addition of oil to fuel for fuel consumption are given. [ABSTRACT FROM AUTHOR]

A numerical simulation of the gasdynamic processes accompanying the formation and propagation of vortex rings obtained with the use of a piston-type generator has been performed. The formation of a vortex ring, the capture of particles of a disperse admixture by it, and their carry by the ring are considered. The numerical calculations were conducted with the use of nonstationary Navier–Stokes equations, and the movement of particles was defined using the discrete-trajectory method. The distribution of the admixture particles in a vortex ring was determined depending on the conditions of its formation. The influence of the characteristics of a vortex ring on the carry of a passive admixture by it was investigated. The reasons for the qualitative and quantitative differences between the losses of particles in a vortex ring in the path of its movement in different regimes are discussed. [ABSTRACT FROM AUTHOR]

The paper analyses the ignition of propane-air fuel mixtures with different excess air ratios near the discharge initiator antenna by a pulsed subcritical microwave discharge. An approximate model that describes the gas dynamics of combustion with a detailed scheme of chemical reactions, external energy supply, and an additional set of reactions, which take into account plasma-chemical effects, is used for calculations. The distributions of temperature, composition of the medium in the vicinity of the antenna and the component-wise mass flow of combustion products after exposure are presented. [ABSTRACT FROM AUTHOR]

Numerical modeling of the interaction of a vortex ring with a normally located flat obstacle was performed based on the nonstationary Navier–Stokes equations, for discretization of which the finite volume method was used. A qualitative picture of the change in the structure of a vortex ring during its interaction with the obstacle is presented. The distributions of pressure in time on the obstacle and the change in the longitudinal force acting on the obstacle are determined. [ABSTRACT FROM AUTHOR]

A numerical simulation of an intense thermionic emission of electrons from the cathode into the air medium in an electrode system has been performed with regard for the possible changes in the voltage across the electrodes and in the electronic work function of the cathode. Spatial distributions of the electrons, the electron energy, the ions, the electric-field strength, and the concentration of the atomic oxygen in the air medium were constructed with the use of a simplified set of kinetic reactions. A possibility of using the thermionic emission of electrons from a cathode for the cooling of the members of flying vehicles with the aim to proof them against heat loads was demonstrated. The numerical calculations have shown that the thermionic emission of electrons from the cathode in a system of electrodes with no protective resistor at a high pressure does not provide a cooling of the system. [ABSTRACT FROM AUTHOR]

An approach to modelling the unsteady axisymmetric vortex flows of a gas-dispersed mixture with an incompressible carrier phase is developed. Numerical modelling of formation of a vortex ring, its capture of dispersed particles and particle transfer is carried out, taking into account the influence of the dispersed phase on the vortex structure of the flow. For numerical simulations, the unsteady Navier–Stokes equations for a viscous incompressible fluid are used. The movement of particles is described based on the discrete-trajectory approach of sample particles. The calculation results make it possible to establish the features of the transfer and behavior of particles of different inertia in vortex rings, as well as changes in the characteristics of the vortex ring in the presence of particles of different sizes and concentrations. [ABSTRACT FROM AUTHOR]

The possibilities of organizing a repetitively pulsed process with given frequency characteristics in a cavity of constant volume with an external energy supply to the working gas mixture are considered. Modelling of gas-dynamic and thermal processes is carried out using the numerical solution of the conjugate heat transfer problem. The gas medium is described on the basis of a viscous compressible gas model. To find the temperature field in the walls of the structure, the equation of non-stationary heat conduction is solved. The conjugation of temperature fields in a gas and a solid is carried out using an iterative procedure. In the calculations, the geometrical parameters of the cavity, the density of the energy supply, the initial pressure, and the composition of the working mixture are varied. The results of calculations obtained in the framework of the one-dimensional and two-dimensional formulation of the problem under the action of both a single pulse and a series of pulses are compared. The results obtained demonstrate the possibility of implementing the required frequency characteristics of the process for given geometric and energy parameters. [ABSTRACT FROM AUTHOR]

The influence of the preliminary ionization of a combustible mixture and the excitation of its molecules by an electron beam and an external electric field on the intensity of burning of this mixture at diff erent rates of its excitation was considered. Results of calculations of the ignition temperatures of a dry mixture of propane and air as well as of their wet mixture are presented. Recommendations for the exposure of a subsonic flow of such a mixture to an electron beam in an external electric field for increasing the efficiency of burning of the mixture are given. [ABSTRACT FROM AUTHOR]

The possibilities of igniting a combustible mixture in a high-speed flow using a microwave streamer discharge are considered. The results of experimental studies of the streamer discharge structure at various pressures are presented. To quantitatively characterize the intensity of combustion of fuel ignited by a microwave discharge, pressure and temperature measurements are used in various sections of the jet in the discharge wake. The results obtained demonstrate the possibility of igniting a model combustible mixture when propane or its mixture with air is sup-plied to the discharge region. The main physical mechanisms responsible for heating the discharge plasma to the ignition temperature of the combustible mixture and their characteristic time scales are revealed. The change in the dimensions of the combustion zone with a decrease in the initial proportion of propane in the mixture is discussed. The minimum duration and minimum level of microwave radiation required to ignite a model combustible mixture under various conditions are determined. [ABSTRACT FROM AUTHOR]

The influence of preliminary ionization and excitation of molecules of a fuel–air mixture when exposed to an electron beam created in an external electric field on increasing the intensity of combustion processes is considered. To study the effect of electron beam plasma on the combustion of a propane–air mixture, a series of experiments were carried out. The characteristics of the propane–air mixture are determined before and after irradiation with an electron beam in the presence and absence of an external electric field. The boundaries of the combined effect of an electron beam and an external electric field are found to increase the efficiency of combustion of a propane–air mixture in a subsonic flow. A physical model of processes in a non-self-sustaining discharge in a subsonic flow of a combustible mixture under known experimental conditions is developed. [ABSTRACT FROM AUTHOR]

A numerical simulation of the conditions for the direct initiation of detonation in the region of a combustible mixture, in which its critical energy is minimum, has been performed using a streamer microwave discharge for the source of detonation initiation. The calculations were conducted on the basis of the model of the two-dimensional detonation in a combustible mixture, flowing in a cylindrical channel, with the use of the system of gas-dynamics and chemical-kinetics equations. The process of detonation initiation was considered as applied to a stoichiometric hydrogen–air mixture flowing in a cylindrical channel at different initial pressures. The requirements for the source of initiation of detonation in a combustible mixture were investigated with respect to the attainment of its critical parameters in practice. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the tribological properties of functional coatings based on the FeO oxide matrix, additionally doped with boron oxide B2O3 and zirconium dioxide ZrO2. The coatings are obtained by highly concentrated short-pulse laser processing of powder compositions previously applied to metal surfaces. The resulting coatings are subject to wear tests under conditions of dry sliding friction with fixation of the friction coefficient, depending on the applied load and the composition of the powder composition. The results give an idea of the degree of change in the coefficient of friction of coatings depending on the powder compositions, as well as their alloying. It has been confirmed that additional alloying with boron oxide has a positive effect on the tribological performance of the coating; in particular, the introduction of 4% boron oxide reduces the coefficient of dry sliding friction to a unique 0.09–0.10. At the same time, a more stable scuffing resistance of friction surfaces is observed, confirmed by studies of surface roughness after testing. A feature of the tribological behavior of the coatings under study is the excessively high temperature background of the tests, reaching 300°C. High temperature and the presence of oxide structures are a catalyst for the formation of stable tribological structures between the rubbing surfaces. The nature of the tribostructures is self-organizing in a "glaze" type and has the property of recovery under friction conditions. After the formation of tribostructures in the friction zone, a significant decrease in temperature and an abrupt decrease in the friction coefficient are observed. With an increase in the amount of boron oxide, the friction coefficient does not decrease so significantly and the minimum value of the dry friction coefficient corresponds to 0.14–0.15, which is caused by a decrease in the cohesive strength of the coating. [ABSTRACT FROM AUTHOR]

A numerical simulation of the ignition of a fuel (propane–air) mixture in a combustion chamber by a subcritical streamer discharge, initiated at the wall of the working channel of this chamber in the electric field with a strength lower than the breakdown one, on the basis of the gas dynamics equation defining the propagation of the combustion products in such a channel, the equation for the chemical kinetics of burning of a gas mixture in it, and the relation defining the formation and development of a streamer discharge in this mixture has been performed for different values of the initial pressure in the channel, the excess of the propane in the gas mixture, and the number of streamer-discharge initiators in the channel. The results of the numerical calculations were compared with the available results of the corresponding physical experiment and experiment on the ignition of an analogous gas mixture by a multipoint spark discharge. [ABSTRACT FROM AUTHOR]

Various electrodynamic models of a combustion chamber are discussed, in which an initiated subcritical streamer discharge is used to ignite the combustible mixture. To localize the discharge in the working chamber, initiators based in half-wave electromagnetic vibrators with resonant properties are used. Based on numerical calculations, the dependences of the structure of the electric fields forming the discharge on the geometric parameters of the discharge initiator were obtained, and the issues of matching the dimensions of the chamber with the radiation generator were considered. The ways of increasing the resulting electromagnetic field in the region of the vibrator for the formation of a discharge with a bulk structure are determined. [ABSTRACT FROM AUTHOR]

An electrodynamic model of a combustion chamber, in which a combustible mixture is ignited by a subcritical streamer discharge initiated with the use of a microwave radiation, is considered. For localization of this discharge in the combustion chamber, its initiator (a vibrator) is positioned parallel to the optical axis of the chamber. On the basis of numerical calculations, the dependences of the structure of the electric field, in which such a discharge is formed, on the geometric parameters of the vibrator and its conductivity have been obtained. For determining an optimum disposition of a vibrator in a combustion chamber, the calculations for its different shifts from the optical axis of the chamber have been performed. The ways of increasing the resultant electromagnetic field in the region of disposition of a vibrator in a combustion chamber for formation of a volume discharge in it were determined. [ABSTRACT FROM AUTHOR]

An electrodynamic model of a combustion chamber, in which a combustible mixture is ignited by a suberitical streamer discharge initiated by a vibrator with the use of a microwave radiation, is presented. For localization of this discharge in the combustion chamber, its initiator (vibrator) is positioned perpendicularly to the optical axis of the chamber. The possibilities of amplification of the electromagnetic field at the poles of the vibrator in the case where a microwave radiation is introduced into the chamber with the use of a plane horn and in the case where a planar waveguide is used for this purpose were considered. Numerical calculations of the electric field in which a subcritical streamer discharge is formed in a combustion chamber have been performed with regard for the geometric parameters of the initiator of this discharge. The ways of amplification of the resultant electromagnetic field in the region of disposition of a vibrator in a combustion chamber were determined for the purpose of obtaining a subcritical streamer discharge with a volumetric structure in the chamber. [ABSTRACT FROM AUTHOR]

The development of tools for modeling the motion of agglomerated particles that feature a complex composition and shape in a flow of combustion products is of interest for problems related to the motion of the condensed phase in internal channels of solid-propellant rocket engines. An approach is developed for modeling the nonsteady-state processes that occur when a viscous incompressible fluid flows around a particle consisting of an aluminum droplet and a condensed oxide particle attached to it. Methods to take into account the sliding of the attached oxide particle over the aluminum droplet surface are proposed. The computational results are used to find the drag and heat-transfer coefficients of a nonspherical particle at flow velocities corresponding to the formation of separation zones. The model developed is a component of a more general mathematical model designed for calculating two-phase flows of combustion products, which is developed on the basis of a multi-scale approach to the simulation of two-phase flows. [ABSTRACT FROM AUTHOR]

The results of computational studies of the gas-dynamic and geometric parameters of supersonic gas jets outflowing from axisymmetric nozzles into a submerged space with strong underexpansion are presented based on the finite volume method and the marching method. [ABSTRACT FROM AUTHOR]

On the basis of analysis of the results of the numerical simulation of a nonstationary gasdynamic processes and conjugate heat transfer in laser cavities of different geometries, the possibility of organization of a pulse-periodic process with definite frequency characteristics in such a cavity was determined depending on the initial pressure of the gas in the cavity, the density of the energy supplied to it, the composition of the gas mixture in the cavity, and the thickness of its walls. The state of the system comprising a gas cavity and its shell under the action of a single laser pulse and a series of laser pulses was simulated. [ABSTRACT FROM AUTHOR]

A technology for renewal and strengthening of a working valve face of a gas distribution mechanism of an internal combustion engine is discussed. A route-and-operational map of the valve repair process has been compiled. Among the main features, the surfacing method (selective laser melting—SLM) and the method of diamond smoothing the surface of a protective-and-renewal coating are highlighted. The processing modes of the part are described. Data on the physical-mechanical characteristics of the coating were obtained. According to the test results, it was concluded that the valve life became double. [ABSTRACT FROM AUTHOR]

The study is dedicated to the peculiarities of implementing the flux limiter of the flow quantity gradient when solving 3D aerodynamic problems using the system of Navier–Stokes equations on unstructured meshes. The paper describes discretisation of the system of Navier–Stokes equations on a finite-volume method and a mathematical model including Spalart–Allmaras turbulence model and the Advection Upstream Splitting Method (AUSM+) computational scheme for convective fluxes that use a second-order approximation scheme for reconstruction of the solution on a facet. A solution of problems with shock wave structures is considered, where, to prevent oscillations at discontinuous solutions, the order of accuracy is reduced due to the implementation of the limiter function of the gradient. In particular, the Venkatakrishnan limiter was chosen. The study analyses this limiter as it impacts the accuracy of the results and monotonicity of the solution. It is shown that, when the limiter is used in a classical formulation, when the operation threshold is based on the characteristic size of the cell of the mesh, it facilitates suppression of non-physical oscillations in the solution and the upgrade of its monotonicity. However, when computing on unstructured meshes, the Venkatakrishnan limiter in this setup can result in the occurrence of the areas of its accidental activation, and that influences the accuracy of the produced result. The Venkatakrishnan limiter is proposed for unstructured meshes, where the formulation of the operation threshold is proposed based on the gas dynamics parameters of the flow. The proposed option of the function is characterized by the absence of parasite regions of accidental activation and ensures its operation only in the region of high gradients. Monotonicity properties, as compared to the classical formulation, are preserved. Constants of operation thresholds are compared for both options using the example of numerical solution of the problem with shock wave processes on different meshes. Recommendations regarding optimum values of these quantities are provided. Problems with a supersonic flow in a channel with a wedge and transonic flow over NACA0012 airfoil were selected for the examination of the limiter functions applicability. The computation was carried out using unstructured meshes consisting of tetrahedrons, truncated hexahedrons, and polyhedrons. The region of accidental activation of the Venkatakrishnan limiter in a classical formulation, and the absence of such regions in case a modified option of the limiter function, is implemented. The analysis of the flow field around a NACA0012 indicates that the proposed improved implementation of the Venkatakrishnan limiter enables an increase in the accuracy of the solution. [ABSTRACT FROM AUTHOR]

A simulation of the large vortices, formed in the flow of an incompressible viscous fluid around a sphere at different Reynolds numbers, has been carried out. Dependences of the local and integral characteristics of such a flow on its initial parameters are presented. Results of the numerical calculations performed were compared with the corresponding experimental data and with the available correlation dependences for the drag and heat-transfer coefficients of a fluid flow around a sphere. [ABSTRACT FROM AUTHOR]

The use of extendible nozzles in propulsion systems is one potential way to increase the nozzle expansion ratio and the specific thrust. Numerical simulation of the supersonic turbulent flow of a viscous compressible gas in a dual-bell nozzle is considered. The displacement of the extendible section of the nozzle from the initial to the working position is taken into account. Numerical calculations are based on the Reynolds-averaged Navier –Stokes equations and equations of the SST turbulence model and sliding meshes. The unsteady structure of the flow formed when the nozzle is restored to service, and the topological features of the flow and relationships between flow quantities are studied. A variation of the force applied to the nozzle walls when the reactive jet flows out is discussed. [ABSTRACT FROM AUTHOR]

Numerical simulation of hydrodynamic processes accompanying the formation and propagation of vortex rings produced by a piston generator has been performed. The influence of the characteristics of a vortex ring on the transfer of a passive impurity is considered. Numerical calculations were carried out using nonstationary Navier– Stokes equations and adaptive grid structures. The geometric and dynamic characteristics of the vortex ring are obtained which correspond to the self-similar law of its dynamics and experimental data. [ABSTRACT FROM AUTHOR]

The flow containing a mixture of gas with spherical particles around an expansion corner is considered. The motion trajectories of discrete particles in a centered rarefaction wave are presented. The results of numerical calculations obtained with the Stokes law for the drag coefficient of an individual particle are compared with ones after corrections for the inertia of the particle and rarefaction of the gas flow. Conclusions are drawn about the effect of the dispersed phase on the distribution of gas flow parameters. [ABSTRACT FROM AUTHOR]

The generation of noise by the flow of a compressible viscous gas over a circular cylinder as a result of the formation of vortices in it and the separation of them from the surface of the cylinder was considered. The sound field of this flow was calculated using the method of simulation of large vortices, and its acoustic characteristics were determined using the method of acoustic analogy based on the solution of the Ffowcs Williams–Hawkings equation. On the basis of the direct numerical simulation data on the indicated flow, its regimes at diff erent Reynolds numbers were investigated. The results of calculation of the acoustic characteristics of this flow within the framework of the two- and three-dimensional approaches to the solution of the Ffowcs Williams–Hawkings equation were compared. A good agreement has been obtained between the calculated gasdynamic and acoustic characteristics of a gas flow over a circular cylinder and the corresponding experimental and calculation data available in the literature. [ABSTRACT FROM AUTHOR]

An experimental study of the ignition and combustion of a combustible propane–air mixture is carried out. The efficiency of two systems for igniting a combustible gas mixture is compared: a traditional technology using conventional spark plugs and a new system based on initiated streamer microwave discharges. The design features of a setup for creating and studying a multifocal microwave discharge system are described. The results of studies of the new microwave system for ignition of the fuel mixture are presented, which are compared with the data of the ignition system based on different numbers of spark discharges. The results of comparative analysis of the two ignition systems are presented for different initial pressures in the combustion chamber and fuel mixture compositions. [ABSTRACT FROM AUTHOR]

Based on the data of a physical experiment, the possibility of increasing the efficiency of combustion of fuel in power plants with the use of a multipoint plasma ignition of a fuel mixture in a cylindrical combustion chamber of such an installation by a subcritical streamer discharge initiated on the combustion chamber surface by a half-wave resonator is discussed. The dependences of the flame front propagation time and the rate of pressure increase in the combustion chamber on the initial pressure and composition of the fuel mixture characterized by the fuel excess coefficient, were studied. Based on the results of measurements, the optimal fuel excess coefficient was determined, which provides the highest pressure and the highest rate of pressure increase in the combustion chamber during streamer ignition of fuel in it. [ABSTRACT FROM AUTHOR]

The development of a supersonic gas flow over a wedge in the process of interaction of a plane shock wave with the wedge was mathematically simulated on the basis of solution of the Euler equations for the nonstationary flow of a compressible inviscid gas in a two-dimensional space with regard for the high-temperature effects of ionization and dissociation of the gas arising in the gas flow due to the balanced chemical reactions proceeding in it. The results of solution of the problem on the supersonic gas flow over a wedge within the framework of the perfect-gas and real-gas models were compared. The influence of the high-temperature effects in this flow on its characteristics and the angle of inclination of a shock wave in it to the wedge was investigated. [ABSTRACT FROM AUTHOR]

To determine the aerodynamic loads on the structural elements of the mobile-deployable landing platform, numerical modeling of the turbulent flow of a viscous compressible gas induced by the rotation of the helicopter rotor is carried out. The flowfield around the helicopter is determined on the basis of numerical calculations, and the pressure distribution on the structural elements of the landing platform is discussed. [ABSTRACT FROM AUTHOR]

The development of efficient and reliable ignition systems for fuel mixtures is of interest for many practical applications associated with the use of combustion power plants. To increase the total flame surface, ensure the reliability of ignition, and increase the combustion rate in the chamber volume and the completeness of combustion of the combustible mixture, multipoint ignition of the fuel mixture using several pulsed spark discharges is used. Based on the data of a physical experiment, a comparison is made of the characteristics of combustion products in the working chamber when using different numbers of igniting spark discharges. The measurements were carried out at different ignition points of the mixture, initial mixture pressures, and fuel excess ratios in the mixture relative to the stoichiometric ratio. The values of the fuel excess coefficient used in the experiment are in a range the boundaries of which are the lower and upper concentration limits of ignition of the propane–air mixture. [ABSTRACT FROM AUTHOR]

The subsonic and supersonic gas jets emanating from a conical nozzle into an immersed space were investigated. The influence of the difference between the total pressure at the inlet of the nozzle and the static pressure in the surrounding medium on the structure of such a jet and its flow dynamics and acoustics were determined and the noise level in the far field of the jet was calculated. The results of numerical simulation of the outflow of a gas from a conical nozzle into an immersed space were compared with the corresponding experimental and calculation data available in the literature. The methods developed for numerical simulation of the flow dynamics and acoustics of gas jets can be used for solving different research and engineering problems as well as for development of new computational algorithms. [ABSTRACT FROM AUTHOR]

A simulation of the vibroacoustic processes proceeding in a long pipe with an obstacle in the form of a circular cylinder, in which a fluid flows, has been performed with regard for the action of the vortices formed downstream of the cylinder on the dynamics of the system. On the basis of the computational procedure developed, the vibroacoustic characteristics of the system have been determined. The distributions of the gasdynamic parameters of the fluid flow in the pipe and the vibroacoustic behavior of the system are discussed. [ABSTRACT FROM AUTHOR]

Features of the simulation of the thermodynamic and gasdynamic processes occurring in devices for reducing the noise level of a shot from a gun were considered. A simulation of large vortices in the nonstationary turbulent flow of powder gases in a muzzle noise reduction device with a silencer representing a shaped channel with several chambers, whose volumes decrease in the direction to the silencer outlet, has been performed. Results of qualitative and quantitative investigations of the initiation, development, and damping of the shock waves in the flow of powder gases, formed as a result of the firing of a shot made from a signal gun, are presented. [ABSTRACT FROM AUTHOR]

The development of efficient and reliable ignition systems for fuel mixtures is of interest for many practical applications associated with the use of combustion power plants. To increase the total flame surface, ensure the reliability of ignition, and increase the combustion rate in the chamber volume and the completeness of combustion of the combustible mixture, multipoint ignition of the fuel mixture using several pulsed spark discharges is used. Based on the data of a physical experiment, a comparison is made of the characteristics of combustion products in the working chamber when using different numbers of igniting spark discharges. The measurements were carried out at different ignition points of the mixture, initial mixture pressures, and fuel excess ratios in the mixture relative to the stoichiometric ratio. The values of the fuel excess coefficient used in the experiment are in a range the boundaries of which are the lower and upper concentration limits of ignition of the propane–air mixture. [ABSTRACT FROM AUTHOR]

To determine the aeroacoustic characteristics of a quadcopter, large eddies of a turbulent flow induced by a four-blade impeller are simulated. The acoustic analogy method based on the integration of the Ffowcs Williams–Hawkings equation is used to calculate the acoustic noise in the far field. A spectral analysis of the acoustic noise generated by the impeller is performed, and the directional patterns of acoustic radiation are plotted for various rotor rotation speeds that simulate the vertical take-off and landing modes. [ABSTRACT FROM AUTHOR]

In this paper, we discuss increasing the fuel efficiency and the efficiency of combustion processes in power plants based on the data of physical and computational experiments. Two ignition systems of a fuel mixture, one of which uses a multipoint pulsed spark discharge, and the other uses a multipoint streamer discharge, are considered. A comparative estimate of the energy efficiency of each of the approaches to the ignition of a fuel mixture is performed, and conclusions about their effectiveness and prospects for use are drawn. [ABSTRACT FROM AUTHOR]

The initiation of a shock wave in the gas space of a pulse generator, the exit of this wave from the generator nozzle, and the formation of a nonstationary gas-jet flow downstream of the nozzle exit section were experimentally investigated and numerically simulated as applied to the installations for the gas-pulse cleaning of heat transfer surfaces. An experimental investigation of the structure of a nonstationary underexpanded supersonic gas jet discharging from the generator nozzle into an immersed space and propagating along a side screen modeling a heat transfer surface cleaned was performed on an air stand. The shock-wave and vortex structures of such a jet were numerically investigated in detail by the method used for the simulation of large vortices. [ABSTRACT FROM AUTHOR]

Possibilities for using general-purpose graphics processing units to simulate compressible gas flows are discussed. Consideration is given to different schemes of computation of flows through the faces of the flow control volume and to the features of their implementation on graphics processing units. A solution of a number of model problems of gas dynamics on graphics processing units is presented and consideration is given to approaches to optimization of the program code connected with the use of different types of memory. A comparison is made between the rates of counting on a graphics processing unit and a central processor using grids having different resolution capabilities and various difference schemes of computation of flows. [ABSTRACT FROM AUTHOR]

Numerical simulation of a super- and hypersonic flow of an inviscid gas around a sharp cone is performed taking into account high-temperature effects. The numerical implementation of a computational procedure designed to find stationary solutions of the gas dynamics equations describing flows around a cone with the real gas properties is carried out. [ABSTRACT FROM AUTHOR]

A numerical simulation of a nonstationary flow of a gas containing inert particle in a shock tube has been perfumed on the basis of the model of mutually penetrating continua, in which the gaseous and dispersed phases are defined by sets of mass, momentum, and energy conservation equations and the equation for the evolution of the dispersed-phase volume fraction. The main equations are hyperbolic, and they are solved using the Godunov-type method of increased accuracy. The shock-wave structure of the gas flow in the working section of the shock tube and the space and time dependences of this flow were determined. The numerical-simulation results are compared with available experimental and calculation data. [ABSTRACT FROM AUTHOR]

A numerical simulation of the flow induced by rotation of the ducted fan blades of a quadcopter is carried out using the vortex-resolving approach that assumes solution of the full Navier–Stokes equations. Based on the numerical simulation results, the aerodynamic characteristics of the ducted fan are determined in various flight modes with asymmetric airflow over the surface swept by the propeller. In the problem formulation, various angles of the ducted fan rotation plane deviation from the vertical were considered for various flight modes of a multicopter type aircraft as well as characteristics of the non-perturbing incident air flow. [ABSTRACT FROM AUTHOR]

The influence of the geometric and regime parameters of a resonance infrared jet-edge generator on the formation, in its resonance tube, of a sound field with a predominant discrete tone at the fundamental frequency of the generator resonant cavity was investigated. A parametric investigation of the self-sustained oscillation processes arising in the resonance tube of the generator as a result of the interaction of a subsonic gas jet and a supersonic one with its resonant cavity has been performed. The nonstationary structure of the gas flow inside this cavity, characteristic of the self-sustained oscillation interaction of a gas jet with an obstacle, is discussed. Prominence is given to the study of the pattern of the gas flow inside the resonant cavity and the amplitude-frequency characteristics of the wave process in it. Recommendations for designing a resonance infrasound jet-edge generator with regard for its use in actual practice are given. [ABSTRACT FROM AUTHOR]

Problems on the development of mathematical models for control of the technological processes of producing powders of metals from their melts and for optimization of these processes were considered. A numerical simulation of the solidification of melt droplets in a turbulent cold-gas jet has been performed with the use of a complex mathematical model, and results of this simulation were used for estimating the influence of different factors on the flying of a melt droplet in a gas flow until it is solidified. [ABSTRACT FROM AUTHOR]

The design of a subsonic jet-edge rod generator of the Hartmann-type oscillator and a scheme of measuring its acoustic parameters are presented. In this generator, unlike the Hartmann oscillator, not a cylindrical gas jet but an annular gas jet, moving along the thin cylindrical rod positioned at the axis of the generator nozzle, is used. A parametric investigation of the gasdynamic and acoustic processes arising in the tubular cavity of such a generator as a result of the interaction of a subsonic gas jet with this cavity has been performed with consideration for the nonstationary structure of the gas flow in the generator cavity. Recommendations on the choice of the design of a jet-edge rod generator of acoustic radiation with regard for its practical application are given. [ABSTRACT FROM AUTHOR]

Supersonic jets are widely used in devices based on a self-oscillation process emerging during the interaction of a gas flow with tubular cavities (gas-jet acoustic emitters). We analyze the mechanisms for sustaining undamped pulsations of pressure and determine the flow field in a tubular cavity during the interaction of an underexpanded supersonic jet with it. We consider the physical pattern of the flow in the cavity of a gas-jet emitter, demonstrate the existence of odd longitudinal modes, and propose wave diagrams for describing the flow in odd longitudinal modes. Wave diagrams are constructed based on analysis of signals from piezoelectric sensors detecting pressure pulsations in a tubular cavity. The flow parameters in the tubular cavity in the longitudinal modes are calculated using the flow velocity–velocity of sound diagram. [ABSTRACT FROM AUTHOR]

In high-pressure gas–jet Hartmann generators, the source of acoustic energy is kinetic energy of a gas jet by the supercritical ratio between the operation and ambient pressure. Under certain conditions, onflow of a supersonic jet to a resonator is accompanied by powerful self-sustained oscillations with irradiation of acoustic waves into the environment and resonator cavity. A model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow. The physical pattern of the flow in the gas–jet generator has been discussed and the study of the dependence of the self-sustained oscillation characteristics on the key gas-dynamic and geometric parameters has been performed. [ABSTRACT FROM AUTHOR]

The gasdynamic processes accompanying the injection of a pulsed gas jet into the diffuser part of a nozzle are considered in relation to the formation of control forces in rocket engines. The gas flow through the injection nozzle is controlled by a rotary damper. The finite volume method and moving mesh technology are used to discretize the Reynolds-averaged Navier–Stokes equations and the equations of the SST turbulence model. The effect of the opening time of the damper on the dynamics of the formation of the control force, as well as the dependence of the traction and energy characteristics of the nozzle on the flow rate of the injected working fluid, are studied. The results of calculations within the non-steady-state and quasi-steady-state problem statement are compared. The formation of the shock wave and vortex structure of the flow is discussed. Conclusions are drawn about the effect of the input parameters of the problem on the coefficient of the traction change. [ABSTRACT FROM AUTHOR]

A simulation of a high-temperature air flow in a nozzle with a nonstationary local power supply has been performed. The thermodynamic processes in this flow were simulated using an approximate model of equilibrium air thermodynamics. Results of a numerical simulation of one-dimensional flows in nozzles with a moving powersupply zone, used in alternating-current plasma generators, are presented. On the basis of the numerical-simulation data obtained, the qualitative patterns of the gasdynamic and thermal processes proceeding in such a nozzle with a nonstationary power supply were analyzed. The results of calculations performed on the basis of the ideal-gas and real-gas models with regard for the physicochemical processes occurring in a real gas at a high temperature were compared. [ABSTRACT FROM AUTHOR]