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It is well known that numerical simulations of high-speed reacting viscous flows, in the framework of state-to-state (STS) formulations, are often prohibitively computationally expensive. In this work, we investigate the possibility of using machine learning algorithms (MLAs) for STS approaches in order to alleviate such issue. As a first step in this direction, we assessed the potential of data-driven regression models based on machine learning to predict the relaxation terms which appear in the r.h.s. of the Euler system of equations for a one-dimensional reacting shock flow in the STS approach for a N2/N binary mixture. Results show that by appropriately choosing the MLA regressor and opportunely tuning the hyperparameters it is possible to achieve accurate predictions compared to the full-scale STS simulation in significantly shorter times. [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]

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]

The hydrogen jet injection through a circular orifice into a transverse supersonic M = 3.38 flow is investigated numerically in the current paper. The 3D computations are performed under the conditions of the experiments by Ben-Yakar (2006). The Delayed Detached Eddy Simulation (DDES) approach is used to describe the transient flow's features. The results of the numerical simulations are compared to the experimental data. A good qualitative agreement between the calculations and the experiment is obtained for the mean flow structure, bow shock position, and jet penetration depth. The use of the scale-resolving DDES approach made it possible to obtain in the calculations large vortex structures developing at the boundary between the jet and the main flow, making a considerable contribution to mixing primary and secondary gases. [ABSTRACT FROM AUTHOR]

In the present paper, a method of local statistical regularization is studied for solving image reconstruction problems in emission tomography with Poisson data. A priori model based on the properties of the object under study is developed. A new reconstruction algorithm MAP-KL based on the Bayesian Maximum a Posteriori (MAP) approach with the a priori probability density defined by the Kullback-Leibler (KL) divergence is proposed. To study the developed local regularization method and to compare the MAP-KL algorithm with the standard maximum likelihood approach, computer simulation of SPECT liver imaging was performed. [ABSTRACT FROM AUTHOR]

The results of an experimental study of a pair of interacting vortices at Mach number of 3 are presented. Laser sheet visualization were performed at various longitudinal coordinate values. The mutual influence of the fact of interaction on the vortex cores size is shown in comparison with the case of an isolated vortex. The results obtained compared to the results of numerical simulation. [ABSTRACT FROM AUTHOR]

The effects of upstream boundary layer disturbances on the dynamics of shock wave/boundary layer interaction (SWBLI) are studied with the direct numerical simulation for the supersonic boundary layer on a flat plate interacting with the incident shock wave generated by a wedge installed at some distance above the plate. [ABSTRACT FROM AUTHOR]

Three-dimensional Navier–Stokes computation of non-equilibrium ionized airflow around the RAM-C II capsule is performed for different flight altitudes. The numerical simulation is performed using one-temperature and multi-temperature approximations. Numerical results show non-symmetrical behavior of macroparameters on windward and leeward sides. Both approximations provide a good agreement between computed peaks of electron densities around the capsule and in-flight data. [ABSTRACT FROM AUTHOR]

Numerical simulation of transonic buffet on a laminar airfoil was performed. The transonic air flow over a wing with the chord of 70 mm was computed (M∞ = 0.628-0.73) at different angles of attack α = 3.5°-7°. Numerical simulation was performed by solving the two-dimensional unsteady Navier-Stokes equations using the ANSYS Fluent package. Two different turbulence models were used: Transition SST (k-w-γ-ReΘ) and k-w SST turbulence model. The computational domain corresponded to the geometry of the test section of the aerodynamic wind tunnel T-325 ITAMSBRAS. In the numerical simulation two periodic non-stationary processes were detected. The first is associated with the pulsations generated in the separation zone that occurs when the shock wave interacts with the boundary layer. This process is characterized by frequencies from 4 to 4.8 kHz, depending on the Mach number and the angle of attack of the wing. The second more lower-frequency non-stationary process with a frequency of ∼200 Hz is associated with the periodic movement of the separation point. Computational results were compared with experimental data. [ABSTRACT FROM AUTHOR]

The effects of the surface undulation on the development of boundary layer instabilities are studied in the supersonic boundary layer. The direct numerical simulations are performed for the boundary layer on a flat plate at flow Mach number M = 6. The surface undulation is considered as the means of passive flow control of the laminar-turbulent transition. It has been found that a wavy portion of the surface located at some distance from the leading edge can significantly reduce the amplitude of fluctuations downstream. The effect of suppressing disturbances significantly increases with increasing both the number of waves on the surface (i.e., the length of the wavy portion), and their depth. [ABSTRACT FROM AUTHOR]

The work proposes the method to design high-rate axisymmetric air intakes through the flow reverse in a respective isoentropic nozzle. Calculation of the flow configuration and parameters in the isoentropic nozzle with the straight characteristic and preset exit Mach number is carried out by the method of characteristics. Then it is suggested that as the flow direction is reversed in the built nozzle contour, flow parameters do not change, but a compression flow appears which corresponds to the flow in the air intake. For comparison, the numerical simulation of the flow in the reversed air intake was made for the enter Mach number M = 6 and in the similar air Busemann intake. The calculations of the non-viscous flow, the total pressure recovery factor in the reversed air intake is 0.996, whereas in the air Busemann intake it is 0.985. The calculations involving the viscosity show that the presence of the boundary layer causes higher losses and reduction of the recovery factor to 0.869 in the the reversed air intake and to 0.832 for the Busemann air intake. [ABSTRACT FROM AUTHOR]

City canyon is a typical urban development configuration with two rows of tall buildings located along the road. Green infrastructure (tree alleys, green hedges/roofs/walls) inside urban canyons are a part of a city planning strategy, and it is actively used by architects around the world to ensure pedestrian comfort, reduce noise and the adverse effects of the urban heat island as well as to combat gaseous and dust pollution. However, a relatively large amount of data indicates a possible adverse effect of alleys with tall trees on the airflow characteristics inside urban canyons. The aim of the work is to numerically investigate the distribution of impurities from vehicles in urban canyons. The paper presents a description of microclimatic models built in ANSYS Fluent. It is based on the Reynolds-averaged Navier-Stokes equations closed with a two-equation k - ε realizable model, and the multi-species approach is used to simulate the impurities dispersion. Models are considered to take into account the influence of green spaces on the mean flow field and impurities concentration in the urban canyon. The simulation model is tested against the CODASC 2008 experimental data. [ABSTRACT FROM AUTHOR]

In this work, we performed a numerical simulation of the problem of the evolution of perturbations in the boundary layer of a plate with a section of a structured surface from a set of slotted closed channels, streamlined by a hypersonic nitrogen flow (M∞ = 8.39, Re1 = 0.82×106 m−1, P∞ = 317.5 Pa, T∞ = 234 K) at an angle of attack α = 5°÷25° and for various values of the surface structure parameters (channel width, distance between channels and channel depth). It is shown that the intensity of the total pressure fluctuations at the upper boundary of the structured surface significantly increases in comparison with the initial perturbation. It is also found an increase in certain frequencies of pressure pulsations associated with the depth of the channels of the structured surface. [ABSTRACT FROM AUTHOR]

The paper proposes a method for determining of an aircraft wing thermal state during flight in icing conditions. The method is based on a probabilistic representation of a boundary value problem for a parabolic type equation and numerical solution of stochastic differential equations. It is assumed that the heat exchange process in a problem of the type under consideration is described quite well by the boundary value problem for the two-dimensional heat equation. The approximate solution definition at a given point is reduced to the numerical simulation of the diffusion random process paths. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of sonic boom near field flow around the NASA Concept 25D (C25D) low-boom supersonic demonstrator configuration are presented. The calculations were carried out for a stationary flow of an ideal gas in a three-dimensional mode with a help of SOLIDWORKS Flow Simulation solver. Comparison with the results of numerical simulations obtained by researchers in the framework of the 2nd AIAA Sonic Boom Prediction Workshop is made. [ABSTRACT FROM AUTHOR]

The paper considers a method for determining the impedance of acoustic liner sample based on numerical simulation of physical processes in resonators at a grazing incidence of a sound wave. The test section of a grazing incidence impedance tube (GIIT) and a model of acoustic liner sample, consisting of 7 honeycomb cells with a depth of 27 mm and 11.9% porous perforate facesheet is simulated. Numerical simulation is based on direct solution of the non-stationary compressible Navier-Stokes equations in a three-dimensional formulation. The pressure-time signals recorded in numerical simulation are processed by the Dean method. The obtained impedance is compared with that educed on full-scale experiment data for a single-layer acoustic liner sample, consisting of 72 honeycomb cells of a similar design. The impedance eduction is performed by minimizing the residual functional, which is the total discrepancy between the calculated and experimental acoustic pressure on the wall of the GIIT. The calculated values of the acoustic pressure are determined by the numerical solution of the Helmholtz equation and the linearized Euler equations for a duct with an impedance wall. [ABSTRACT FROM AUTHOR]

Numerical and theoretical stability studies are conducted for a supersonic M = 2.0 flow over a flat plate with a spanwise strip of distributed suction. Propagation of artificially excited 3D wave trains relevant to the first-mode instability are considered. Direct numerical simulations (DNS) as well as assessments based on the linear stability theory (LST) are performed using the in-house code "HSFlow++" (High Speed Flow solver). It is shown that, despite strong spatial nonuniformities of the mean flow near the suction strip ends, the e-N method based on the local-parallel LST gives reasonable estimates of the laminar flow control performance of the suction strip. [ABSTRACT FROM AUTHOR]

A method was developed for prediction of the acoustic characteristics of resonant liner samples based on numerical simulation of physical processes in a normal incidence interferometer. Numerical simulation was performed based on direct solution of the non-stationary compressible Navier-Stokes equations in a three-dimensional formulation. The studies were carried out for full-scale multilayer samples of honeycomb acoustic liners with geometric characteristics close to those actually used in aircraft engines. The results of computations were compared with results of prediction based on semiempirical model and with results of natural experiments on normal incidence interferometer. It was revealed that the acoustic characteristics obtained by numerical simulation are in better agreement with the results of natural experiments than those determined by semiempirical model. [ABSTRACT FROM AUTHOR]

A hybrid model has been developed for calculating the flow of C2H2 gas in a cylindrical channel taking into account the mechanisms of heat exchange of gases with the surface and adsorption of molecules on the channel surface (molecular dynamics method and Monte Carlo method). A set of programs has been developed and calculations have been made of the deposition and / or scattering of acetylene molecules on the surface of a silicon substrate within the framework of the molecular dynamics method, taking into account the most accurate model of the atom-atom interaction of molecules with each other and with the substrate atoms. Combinations of the angle of incidence of acetylene on the substrate and the velocity of the center of mass of the molecule at which adsorption occurs are revealed. [ABSTRACT FROM AUTHOR]

Atmospherical particles can be the main reason for boundary layer instability, leading to a laminar-turbulent transition on aerodynamically smooth bodies. On the height of about 20-30 km, the concentration of submicron particles is relatively high. Such particles are able to hit leading edges of an aircraft, exciting wave packets of first and/or second mode. During propagating downstream, these wave packets are growing, reaching critical amplitude and turning into turbulent spots. The article introduces the results of numerical computation of boundary layer receptivity to solid particles near the blunt leading edge of the plate in flow with Mach number 6. [ABSTRACT FROM AUTHOR]

The presence of the point of maximum amplification on the upswept parabolic wing at Mach 3 has been verified by using direct numerical simulation. Previously, this point was detected using linear stability analysis. The general pattern in the development of instabilities in the boundary layer is confirmed. The maximum amplitude of disturbances in the boundary layer decreases downstream of some point. This is a promising result for the design of civil supersonic aircraft with the upswept laminar wing. [ABSTRACT FROM AUTHOR]

In the current work the preliminary results of numerical simulations of detonation wave propagation with detailed hy- drocarbon chemical mechanisms are presented. 1D and 2D cases are investigated. All simulations are conducted using an in-home code solving the chemically reacting Euler equations on supercomputers with GPUs. Four chemical models are considered: AFRL model, Singh–Jachimowski model, Varatharajan–Williams model and GRI-Mech 3.0 model. Due to complexity of GRI-Mech 3.0 model it is not used for 2D numerical simulations of detonation wave propagation. For all chemical models the Chapman-Jouguet velocity is obtained, the ignition delay is determined and the Zeldovich–Neumann–Doering solution is obtained in order to compare how suitable they are for numerical simulations of detonations. The 2D Euler equations are solved for an ethylene/oxygen/nitrogen mixture using high-order shock-capturing TVD schemes and a finite-rate chemistry solver. The sizes of detonation cells obtained with different models are compared with each other and experimental data. [ABSTRACT FROM AUTHOR]

In this paper we present a numerical study of two streamwise supersonic vortices interaction. A pair of vortices was generated by two coaxial straight wings with sharp leading and trailing edges. Mach number of incoming flow was M∞ = 3. Two configurations are considered: a pair of co-rotating vortices and a pair of counter-rotating vortices. In the case of counter-rotating vortices the wings attack angle was 10 degrees. In the case of co-rotating vortices the attack angle of one of the wings was 10 degrees, the attack angle of other one was -10 degrees. Numerical data were obtained in the domain of 10 wing chords downstream from a wings axis by a computational model based on the URANS equations with SA turbulence model. Numerical simulations were performed on the hybrid supercomputing system K-60 at the Keldysh Institute of Applied Mathematics RAS using the developed software package ARES for 3D turbulent flows modeling on high performance computing systems. This work is a continuation of the series of author's works dedicated to the supersonic wingtip vortices. [ABSTRACT FROM AUTHOR]

Underground mining of coal seams often causes problems associated with the imbalance of the natural coal-methane system. In some cases, during anthropogenic action on the coal seam, an extremely large amount of methane is released, which leads to disasters—methane explosions or emissions of coal and gas, in other cases, very little free methane is released, which greatly complicates the commercial production of coal mine methane. Dynamic impact is one of the tools for managing the conditions of coal seams. As a result of explosive action, extended cracks can form in the coal seam for it degassing. The aim of the work is to consider the type of failure to find ways to optimize the explosive impact on the coal seam. This may contribute to the development of a drilling and blasting passport, depending on the objectives of this impact. To this goal, the work uses a joint model of a gas-saturated coal seam to describe the hierarchical relationship between explosive damage to the coal seam and gas evolution [1]. Based on this model, using the numerical simulation by the smoothed particle hydrodynamics method (SPH) [2, 3], the development of the fracture zone is studied and the stress-strain state of the formation near the face before and after the explosion is determined. The obtained patterns help to predict the reaction of coal to a dynamic effect. This is of great importance for the technology of preliminary degassing of coal seams and for the technology of provoking controlled emissions of coal and gas. [ABSTRACT FROM AUTHOR]

The numerical scratching of titanium substrates with coatings based on the Ti-Al-Ta-N and Ti-Al-Ta-N systems is in the focus of the paper. In the case of Ti-Al-N coating, 25% of Ti atoms in the cubic lattice of TiN were randomly replaced by Al atoms. Four-component coating was set as Ti31Al33Ta36N with random distribution of Ta and Al. The studies were carried out using the molecular dynamics method. It was shown that for the Ti75Al25N coating the number of atoms with packaging different from the original is much larger than for the sample with the Ti31Al33Ta36N coating. Moreover the number of atoms with a local configuration different from the initial one in the sample with the ternary coating penetrates deeper into the bulk of the titanium substrate. The results of computer simulations correlate well with available data of experimental studies. [ABSTRACT FROM AUTHOR]

This work shows the results of the numerical investigation of the stress-state and the fracture of zirconia ceramic specimens under Brazilian test conditions. To account for the heterogeneous structure of the specimens in the simulation two different statistical computer models were considered. In the models, a random scatter of the shear strength amounts to ±5% and ±50%. The behavior of zirconia ceramic specimens is described by the Drucker–Prager model with non-associated plastic flow rule. It is shown that the failure in the specimen with scatter 5% occurs at higher stresses compared to the specimen with scatter 50%. Also, it is noted that the crack propagates more quickly in the specimen with scatter 5% and the bigger part of the specimen is fractured. The cracks branching and material fragmentation are observed. The numerical simulation showed good agreement with the experiment. [ABSTRACT FROM AUTHOR]

The energies of quasistationary states and the activation energy of electron transfer between the active oxygen form O2− and the active center of the antioxidant enzyme Cu, Zn-SOD in a continuous dielectric medium are calculated using the Marcus theory. The calculations were carried out using the CPCM continuum model of the solvent with the B3LYP hybrid density functional in the basis set 6-31G(d,p) of the ORCA software package. The results are obtained for media with a dielectric constant ε = 1 (vacuum), ε = 3–4 (protein) and ε = 81 (water). It was shown that with increasing solvent polarity, electron transfer is hampered by an increase in activation energy and reorganization energy, despite a decrease in the total energy of the complex in the medium. [ABSTRACT FROM AUTHOR]

The paper investigates the deformation behavior of a mechanical metamaterial. The metamaterial is made up of tetrachiral elements. An analytical solution is obtained for the deformation behavior of a unit cell of the metamaterial depending on its parameters. The results of the analytical solution were used for numerical modeling. The computer FEM model was built using beam elements. The numerical solution of the mechanical loading of the metamaterial was performed in the static case of the linear theory of elasticity. In the course of numerical simulation of the uniaxial loading of the mechanical metamaterial, it was found that the specimen inclines when elongated. The difference in inclination angles between the right and left sides of the specimen is probably related to the rotation of the ring in the tetrachiral structure. [ABSTRACT FROM AUTHOR]

In this paper, the states of stress and strain in the deep structures in the Yakutsk-Vilyui large igneous province (LIP) are numerically analyzed. The "Craton-1980" profile with 60 km depth was chosen because it is characteristic for the Yakutsk-Vilyui LIP and contains deformed crystalline foundation and the upper mantle layer. This geological profile was obtained by deep seismic sounding surveys. Using the "Craton-1980" profile data a 2D computer structural model was constructed. To solve the posed problem, a model of the continental yield stress envelopes (YSE) was used in which the strength properties of Earth's crust layers change in accordance with depth and due to the influence of heat flow from the mantle layer. To describe the inelastic properties, the use of Nikolaevskiy's elastoplastic model was made. Numerical simulation allowed for revealing the regions in the lithosphere responsible for the formation of stress concentrations and inelastic strain localization. The location of these regions was shown to be determined not only by the heterogeneous layers in Earth's crust with curved interfaces but also by pronounced non-monotonic dependence of strength with depth. [ABSTRACT FROM AUTHOR]

The article analyzes the gas-dynamic flow pattern, which is formed near an axisymmetric body moving in an axisymmetric channel of infinite length. The full cycle of body movement is considered, including acceleration from a state of rest to high supersonic speeds and deceleration to a complete stop. The most interesting aspects of the problem are the processes of transition of the flow near the body to supersonic, during acceleration, and back to subsonic with the leading shock wave in front, during braking. Demonstration of the nature and sequence of changes in the gas dynamic flow pattern in the paper is presented as the results of numerical simulation of acceleration and deceleration processes. We consider a favorable geometric case with the ratio of the channel area and the duct area between the body and the channel wall equal to Fneck/Foverpass = 0.84. [ABSTRACT FROM AUTHOR]

The non-linear development of the slow and fast supersonic instabilities and their mutual interactions are studied in the mixing layer at the convective Mach number Mc=4 with the numerical simulation. Spatial evolution of the instability is considered. The unstable waves are excited at the inflow boundary in the form of linear stability eigenfunctions. The simulation results show that the disturbance of the slow mode grows rapidly at the initial stage and reaches a nonlinear development regime with the formation of vortex structures in the form of curls in the lower critical layer. The development of the fast-mode disturbance at the initial stage is much slower. The disturbance gradually reaches the regime of nonlinear growth with the formation of elongated vortex structures in the upper critical layer. In both cases, intensive radiation of waves in the external streams is observed. [ABSTRACT FROM AUTHOR]

The authors proposed new approaches to modeling the solid-liquid and liquid-solid phase transitions using the core-Cu-shell-Ag system as an example. It was revealed that the presence of an insignificant thermodynamically nonequilibrium state in the system is a key factor leading to the emergence and development of crystallization, which must be taken into account when modeling phase transitions. [ABSTRACT FROM AUTHOR]

In the paper, the results of numerical modeling are presented of the 3D turbulent flows in a channel with backward-facing step, and argon jets injected into the supersonic crossflow. The numerical simulations are carried out under the conditions of experiments performed at the hot-shot wind tunnel IT-302M ITAM SB RAS for flow parameters as follows: Mach number at the entrance of the channel M=3.86, the total temperature T0 = 1650 K, and the total pressure P0 = 5.5 MPa. Sound jets of argon are supplied from two circle orifices located opposite each other on the channel walls before the backward-facing step. A series of calculations have been performed with a change in the jet supply pressure from 1 to 5 MPa, which ensures the variation in the jet-to-crossflow momentum flux ratio in the range J = 0.7 ÷ 6. Mathematical modeling was carried out using ANSYS Fluent based on the Reynolds-Averaged Navier- Stokes equations supplemented by the k-m SST turbulence model. A comparison of the calculated and experimental data on the static pressure distributions on the walls indicates a satisfactory agreement. The calculated results made it possible to obtain a clearer understanding of the 3D flow structure in the channel and reveal the influence of the injection pressure on the level of mixing along the channel. The obtained data can be used to select the parameters for the injection of heavy hydrocarbon fuels in the combustion chamber of the scramjet engine at flight Mach numbers M > 8. [ABSTRACT FROM AUTHOR]

The study is devoted to numerical modeling of the flow pattern in the two-channel tract of an acoustic- convective dryer (ACD). The data were obtained as a result of mathematical modeling using the ANSYS Fluent software package. To solve the problem three-dimensional Navier-Stokes equations averaged by Reynolds supplemented with the k-ω turbulence model were applied. The fields of velocity and pressure were quantified. The process of forming an acoustic-convective flow in the channels is described and visualized. A connection has been established between the wave processes occurring in the ACD and the generated high-intensity sound. The results of numerical modeling are in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The paper describes the results of numerical simulations of a supersonic (M= 7) flow around a cylinder with a frontal gas-permeable porous insert. A comparative analysis of four skeleton models of high-porosity cellular materials with regular arrangement of skeleton elements is performed: model composed of a set of coaxial rings of different diameters and three models composed of spheres with different spatial positions (intersecting hollow spheres, hollow spheres connected by cylindrical channels, and non-intersecting solid spheres). The computed drag coefficients are compared to the experimental results obtained in the T-327 wind tunnel based at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences (ITAM SB RAS). The model composed of coaxial rings and the model composed of non-intersecting solid spheres are found to provide the best agreement with the measured aerodynamic coefficients. [ABSTRACT FROM AUTHOR]

The reservoir systems often contain fractures of different lengths and conductivity. The dual porosity - dual per-meability (DPDP) model and the discrete crack model (DFM) are integrated to achieve computational efficiency and accuracy of numerical simulation of fractured reservoirs. In this paper, DPDP and DFM models are combined to simulate fluid flow in fractured poroelastic media. The control volumes method was used to discretize both flow and poroelasticity equations. Synthetic model of a reservoir with a system of multiscale fractures was used to show the influence of the stress-strain state on the fluid flow. [ABSTRACT FROM AUTHOR]

The processes of detonation propagation in channels with linear expansion filled with aluminum - oxygen suspensions of different concentrations are analyzed on the base of numerical simulation of two-dimensional flows. The aim of the work is to determine the effect of the ratio of oxidizer to fuel on the critical conditions of detonation propagation. A semi-empirical model of aluminum detonation is used, which takes into account the dependence of the energy release of the combustion reaction and the portion of unburnt particles on the mass loading of particles. It was found that pre-stoichiometric mixtures are characterized by higher detonation ability than the stoichiometric and super- stoichiometric mixtures. [ABSTRACT FROM AUTHOR]

The paper describes validation of a multidimensional semi-Lagrangian method with the use of a conservative fifth-order WENO scheme on the basis of computer simulation of models of rotating circular solid disks. Implementation of this method on GPU is briefly described. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study of the fracture strength of compact tension specimens and double cantilever beams made of polymethylmethacrylate (PMMA) under tension was carried out. The critical loads and crack propagation paths for these samples under pure mode I loading conditions differ markedly. Energy-based theoretical model, which allows predicting the instability of the crack growth path, is presented. The theoretical model takes into account both the singular term of stress in front of the crack tip and the first non-singular term known as T-stress. To verify the theoretical model, the experimental results obtained in fracture test on several mode I cracked samples are used. Computer simulation of crack propagation in a geometrically and physically nonlinear formulation has been performed. The experimental data are compared with the calculation results. It is shown that the instability of the crack path substantially depends on the geometry and can be prevented by changing the sample geometry or type of load. [ABSTRACT FROM AUTHOR]

The development of the Rayleigh-Taylor instability is studied by solving numerically two-dimensional Navier-Stokes equations for a viscous compressible gas in a uniform field of an external body force. The main attention is paid to the change in the flow pattern with an increase in the Knudsen number (and, accordingly, a decrease in the inversely proportional Reynolds number) and the increasing influence of the effects of viscosity and flow rarefaction. It is determined at what value of the Knudsen number the development of secondary Kelvin-Helmholtz instability is suppressed. Usually the Kelvin-Helmholtz instability plays the main role in the emergence of small-scale pulsations and the transition to turbulence. The dependence of the growth rate of the spike formed by the heavier gas on the flow rarefaction is studied. [ABSTRACT FROM AUTHOR]

Module of HyCFS-R numerical code for the simulation of chemically reacting gas/particle suspensions based on the Euler–Euler approach is verified on the problem of detonation wave propagating in channel. The grid convergence and 3D effects are studied. Numerical simulation results are compared with data available in the literature. [ABSTRACT FROM AUTHOR]

With the rapid development of numerical methods and computer systems in recent years, it has become possible to model complex multidimensional flows on the basis of the Boltzmann equation. For the first time, numerical simulations of the development of Rayleigh-Taylor instability is performed based on the solution of both the Boltzmann equation and the model kinetic equation. This paper is aimed at the identification of kinetic effects and estimation of the degree of flow non-equilibrium. For this purpose, the distribution functions obtained from kinetic simulations are compared with the Navier-Stokes distribution function. [ABSTRACT FROM AUTHOR]

The article presents an investigation of gas flow that occurs under typical for cold spraying conditions when supersonic gas jet, that exhausts from De Laval nozzle, and impinges on mask with a round perforation, behind that substrate is placed. Numerical simulation was made using software ANSYS Fluent. Shadowgraph was used to obtain images of gas flow. The results obtained were analyzed and compared. [ABSTRACT FROM AUTHOR]

Numerical simulations of detonation wave propagation in a channel are performed and the formation of the detonation wave multifront structure is studied. An in-house numerical code running on hybrid supercomputers is employed for the numerical simulations. The code is written in C++ with the use of MPI, OpenMP and CUDA parallel technologies. Four different chemical reaction mechanisms for description of hydrogen/oxygen mixture combustion are considered. The mechanisms are compared in terms of the Chapman-Jouguet detonation speed, the predicted number of detonation cells and the shape of detonation wave front. [ABSTRACT FROM AUTHOR]

The orientation dynamics of nematic liquid crystals (NLCs) is rotation of the director, i.e. a unit vector representing the preferred direction of orientation of molecules, under the action of elastic forces and an electromagnetic field (EMF). A numerical method for solving the equations of the orientation dynamics is proposed and details of its implementation are discussed. A special attention is paid to coupling of numerical solvers for the orientation dynamics of NLCs and for Maxwell's equations describing the light propagation in an anisotropic non-uniform medium. A numerical solution of the problem of the Fréedericksz transition is compared with its analytical solution, other examples of numerical simulations of physical phenomena in liquid-crystalline media interacting with electromagnetic waves are given. [ABSTRACT FROM AUTHOR]