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A numerical simulation of an unsteady gas flow containing inert solid particles in a shock tube is carried out using the interpenetrating continuum model. The gas and dispersed phases are characterized by governing equations that express the concepts of mass, momentum, and energy conservation as well as an equation that shows the change of the volume fraction of the dispersed phase. Using a Godunov-type approach, the hyperbolic governing equations are solved numerically with an increased order of accuracy. The working section of the shock tube containing air and solid particles of various sizes is considered. The shock wave structure is discussed and computational results provide the spatial and temporal dependencies of the particle concentration and other flow quantities. The numerical simulation results are compared with available experimental and computational data. [ABSTRACT FROM AUTHOR]

Aim of the study: This study examines numerical methods for solving the problems in gas dynamics, which are based on an exact or approximate solution to the problem of breakdown of an arbitrary discontinuity (the Riemann problem). Results: Comparative analysis of finite difference schemes for the Euler equations integration is conducted on the basis of an exact or approximate solution to the problem of an arbitrary discontinuity breakdown. An approach to the numerical solution of the Euler equations governing inviscid compressible gas flow is developed on the basis of the finite volume method and finite difference schemes for flow calculation of various degrees of accuracy. Calculation results show that monotonic derivative correction provides numerical solution uniformity in the breakdown neighborhood. On one hand, it prevents the formation of new extremum points, thereby providing monotonicity, but on the other hand, it causes smoothing of existing minimums and maximums and accuracy loss. Conclusions: The developed numerical calculation method makes it possible to perform high-accuracy calculations of flows with strong non-stationary shock and detonation waves and no nonphysical solution oscillations on the shock wave front.

In this article we reviewed the main concepts of detonative combustion. Concepts of slow and fast combustion, of detonation adiabat are introduced. Landmark works on experimental and semi-empirical detonation study are presented. We reviewed Chapman-Jouguet stationary detonation and spin detonation. Various mathematical model of detonation wave have been reviewed as well. Works describing study of the instability and complex structure of the detonation wave front are presented. Numerical methods, results of parametric and asymptotic analysis of detonation propagation in channels of various forms are reviewed. It is shown that initiation of detonation is the main problem. Its various possible forms have been discussed. Laser ignition of fuel-air mixture was discussed separately and potential advantages of such initiation were demonstrated.

We present the most relevant works on jet engine design that utilize thermodynamic cycle of detonative combustion. Detonation engines of various concepts, pulse detonation, rotational and engine with stationary detonation wave, are reviewed. Main trends in detonation engine development are discussed. The most important works that carried out theoretical, experimental and computational research and their parametrical optimization are described. Relevant for nearest time problems and directions of research are formulated. [For "Detonation Jet Engine. Part 1--Thermodynamic Cycle," see EJ1115570.]

In this article we reviewed the shock wave oscillation that occurs when supersonic flows interact with conic, blunt or flat nose of aircraft, taking into account the aerospike attached to it. The main attention was paid to the problem of numerical modeling of such oscillation, flow regime classification, and cases where aerospike attachment can lead to drag reduction. It is established that the effective computation methods, that allow acquisition and recreation of their oscillation, are based on either technique with pre-allocation on gas-dynamic discontinuities or high accuracy difference schemes. Moreover, the application of standard straight-through methods leads to appearance of non-physical artifacts in solution: solution's oscillation on shock waves, weak rarefaction waves and instability streets of Kelvin-Helmholtz type. The practical value is that the research findings may be useful for future investigations on the problem of numerical modeling of shock wave oscillation.

We present the most relevant works on jet engine design that utilize thermodynamic cycle of detonative combustion. The efficiency advantages of thermodynamic detonative combustion cycle over Humphrey combustion cycle at constant volume and Brayton combustion cycle at constant pressure were demonstrated. An ideal Ficket-Jacobs detonation cycle, and the thermodynamic cycle of real detonation engine that utilizes over compressed detonation were discussed. Main trends in development of detonation engines were described. Relevant for nearest time problems and directions of research were formulated.

When a shock wave interacts with a contact discontinuity, there may appear a reflected rarefaction wave, a deflected contact discontinuity and a refracted supersonic shock. The numerical simulation of shock wave refraction at a plane contact discontinuity separating gases with different densities is performed. Euler equations describing inviscid compressible flow were discretized using the finite volume method on unstructured meshes and WENO schemes. Time integration was performed using a third-order Runge-Kutta method. The wave structure resulting from regular shock refraction is determined allowing its properties to be explored. In order to visualize and interpret the results of numerical calculations, a procedure for identifying and classifying gas-dynamic discontinuities was applied. The procedure employed dynamic consistency conditions and digital image processing methods to determine flow structure and its quantitative characteristics. The results of the numerical and experimental visualizations were compared (shadow patterns, schlieren images, interferograms). The results computed are in an agreement with the theoretical and experimental predictions of a regular refraction of a shock wave on an inclined contact discontinuity.

Ensuring the safety of space flights and solving the problems of reducing acoustic loads during the launch of space vehicles requires not only the development of new technical systems for launch complexes, but also methods for the numerical simulation of fluid and aeroacoustic fields generated by supersonic jets. The growing regulations for space vehicle noise also explain the interest in developing models and techniques that anticipate flow and the aeroacoustic characteristics of supersonic jets. Together with integral techniques for computing far-field noise, development of relevant mathematical models and implementation of numerical tools, the concepts of computational fluid dynamics (CFD) and computational aeroacoustics (CAA) are covered. The noise generated by a supersonic underexpanded jet is used to illustrate the capabilities of current numerical modelling and simulation tools. The jet structure, flow properties, and aeroacoustic quantities are affected by the nozzle pressure ratio. The outcomes of numerical simulation are contrasted with existing experimental and computational data. The available numerical modelling and simulation tools facilitate the development of novel computational methods and methodologies for challenges in CFD and CAA, in addition to solving research and engineering problems. [ABSTRACT FROM AUTHOR]

The correct qualification of a crime provides the basis for achieving the goals of criminal liability, including sentencing a just punishment. During qualification, law enforcement agencies (investigative bodies, inquiry bodies, and court) often face problems caused by contradictions in criminal law regulation (a gap in law, defects in law, legal conflicts, evaluation categories of law, etc.). According to the authors, it is possible to eliminate the contradictions of criminal law regulation by applying the principles of criminal law as a direct regulator of criminal law relations. Purpose of the research: to identify the problems of qualifying crimes in the modern practice of preliminary investigation bodies and courts, as well as to determine the place and role of the principles of criminal law in the process. Framework of the research. The research was carried out with general scientific methods (dialectical, statistical, comparative legal); in addition, methods of analysis, deduction, synthesis, as well as a formally legal method, were used in the research. Conclusions: the authors draw the conclusion that the principles of criminal law should be considered as an independent fundamental form of Russian law.

An efficient finite element analysis/computational fluid dynamics (FEA/CFD) thermal coupling technique has been developed and demonstrated. The thermal coupling is achieved by an iterative procedure between FEA and CFD calculations. Communication between FEA and CFD calculations ensures continuity of temperature and heat flux. In the procedure, the FEA simulation is treated as unsteady for a given transient cycle. To speed up the thermal coupling, steady CFD calculations are employed, considering that fluid flow time scales are much shorter than those for the solid heat conduction and therefore the influence of unsteadiness in fluid regions is negligible. To facilitate the thermal coupling, the procedure is designed to allow a set of CFD models to be defined at key time points/intervals in the transient cycle and to be invoked during the coupling process at specified time points. To further enhance computational efficiency, a 'frozen flow' or 'energy equation only' coupling option was also developed, where only the energy equation is solved, while the flow is frozen in CFD simulation during the thermal coupling process for specified time intervals. This option has proven very useful in practice, as the flow is found to be unaffected by the thermal boundary conditions over certain time intervals. The FEA solver employed is an in-house code, and the coupling has been implemented for two different CFD solvers: a commercial code and an in-house code. Test cases include an industrial low pressure (LP) turbine and a high pressure (HP) compressor, with CFD modeling of the LP turbine disk cavity and the HP compressor drive cone cavity flows, respectively. Good agreement of wall temperatures with the industrial rig test data was observed. It is shown that the coupled solutions can be obtained in sufficiently short turn-around times (typically within a week)for use in design. [DOI: 10.1115/1.3147105]