Modeling of Hypersonic Flows: Influence of the Starting Conditions of the Algorithm on the Final Solution in the Vicinity of Bifurcation Points

We investigate the influence of the starting conditions of the computational algorithm (a discrete analog of the initial data of a continuous differential problem) on the trajectory of calculation advancement in the space of solutions and on the obtained final (stationary, quasistationary, or nonstationary) solutions of Navier–Stokes equations for mathematical modeling of highspeed gas flows. Particular consideration is given to the analysis of the behavior of trajectories in the vicinity of the bifurcation points of branching of solutions. Questions associated with the carbuncle effect — a special kind of instability of a part of the shock front at a hypersonic flow over the front part of a bluntnosed body — are discussed.     

Propagation of HF radio waves over sloping coastal land

The field of a TM wave at a reception point over sloping coastal land, farther than a wavelength from the sea, has been calculated for a transmitting element located infinitely far away over a flat sea. The field obtained is normalized to that of a wave approaching the water/land boundary from infinity. A transmitting element placed both at some elevation angle and on the surface of the sea has been considered. In both instances, simple formulas providing fast computation of the field have been obtained by employing the integral equation approach formulated in terms of the normalized surface impedance. It has been found that the sloping land to some extent compensates for power losses in the ground and may even enhance the power density of high-frequency waves coming from low elevation angles. The expressions obtained remain valid for flat ground in place of sea. In this instance, the permittivity and conductivity of the sea should simply be substituted by those of the ground     

Periclase-Carbon Refractories for Operation in the Mouth of a Converter Vessel

The performance of periclase-carbon refractories cemented with a phenolic bond that are intended for use in the lining of the cone section of the oxygen converter vessel has been studied by x-ray diffraction and petrography techniques. The results obtained provide a basis for further improvement of the oxygen converter technology and refractory fabrication.__________Translated from Novye Ogneupory, No. 2, pp. 23 – 25, February, 2005.Based on materials reported to the 8th Congress of Steelmakers (18 – 22 October, 2004, Nizhny Tagil, Russia).     

Features of Segregation of Doping Impurities of V(a) Subgroup Elements on Angular Configurations of the Silicon/Silicon Dioxide Oxidation Boundary

On the basis of computer simulation of the physicochemical process of segregation of doping impurities implanted in the basic material (silicon), the features of ejection of V(a) subgroup elements (phosphorus, arsenic, and antimony) on the angular configurations of the silicon/silicon dioxide oxidation boundary are investigated.     

Thermal and force loads on the vehicle surface in high-velocity motion in the earth’s atmosphere

Consideration has been given to a number of aspects of mathematical modeling of a high-velocity flight in the earth’s atmosphere in a wide range of variation of the determining parameters. Super-and hypersonic gas flow past flying vehicles has been investigated based on computer-aided calculations with allowance for its actual properties. Data on the distribution of gasdynamic parameters in the flow field, including thermal and force loads on the surface, have been obtained and analyzed. The issues of applying today’s information technologies to archiving scientific knowledge obtained in electronic databases of a specialized Internet center and their dissemination via the Global Network have been discussed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 2, pp. 338–344, March–April, 2008.     

Shock-wave modes of flow at the inlet to the diffuser of a hypersonic scramjet engine: The effect of flight altitude and velocity

Analytical methods are used to investigate shock-wave structures characterized by different types of interaction (Mach or regular) of pressure shocks arising in hypersonic flows. The method of effective adiabatic exponent is used to include the actual properties of the atmosphere. Computer codes are developed to determine the topology of shock-wave patterns and to calculate the gas- and thermodynamic parameters in different zones of flow between shock fronts in the flight altitude range from zero to 100 km and in the flight velocity range from 2 to 7 km/s. The limits of Mach-regular reflection transition are obtained, and domains of dual solution are determined in which interaction of both types is possible.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 057–070. Original Russian Text Copyright © 2005 by G. A. Tarnavskii.     

Decomposition of Methods and Parallelization of Algorithms for Solving Aerodynamics and Physical Gas Dynamics Problems: Computer System Potok-3

This paper is aimed at developing modern computer technologies and methods of concurrent programming designed to improve the efficiency of solving fundamental scientific and applied problems of numerical simulation in aerodynamics and physical gas dynamics. Theoretical issues concerning the design of aircraft involving large amounts of computations are also examined. This paper is focused on theoretical issues of paralleling available methods and algorithms for solving complex integro-differential systems of equations. A number of paralleling methods are considered based on various types of decomposition of the original problem into several subproblems that can be solved concurrently (decomposition by physicomathematical processes of the technological chain of computations and by the corresponding processes that can be performed concurrently (horizontal paralleling), and decomposition by the computational geometric domains and by the corresponding processes that can be performed concurrently (vertical paralleling)). The efficiency of these methods is compared and the optimal paralleling method is found. The results of the theoretical study are used in developing the third-generation package of programs for solving aerodynamics and gas dynamics problems called Potok-3.     

Design of semiconductor materials for electronics. Segment of the technological process: Annealing of the base substrate and formation of a nanostructure of dopants

For one production segment of designing semiconductor materials with given electrophysical properties, computer simulation of a number of basic technological physicochemical processes has been performed. With the use of high-resolution algorithms, the dynamics of thermal oxidation of the base material (silicon) and the evolution of the SiO₂/Si and SiO₂/O₂ oxide film interfaces have been investigated. Simulation of the process of segregation of the acceptor and donor dopants (boron and phosphorus) in the base material at the SiO₂/ Si oxidation wave front has been performed. For the “trench”-type geometry of the substrate surface, the distributions of boron and phosphorus concentrations have been obtained. It has been shown that the uniform (at the initial instant of time) distribution of dopant concentrations in the base material transforms to a distribution of narrowly-localized (of width about 65 nm) high-intensity peaks. Such nanostructures of donor and acceptor impurities in the substrate provide the required semiconductor electrophysical properties of the material. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 994–1004, September–October, 2008.     

Influence of Flow Angularities in a Hypersonic Ramjet Diffuser on the Formation of the Shock‐Wave Structure of the Real Gas Flow

We have investigated the shockwave structures arising at the entrance to the engine section of hypersonic aircraft and the influence on the process of their formation of the flow angularity after oblique shock fronts incident inside the diffuser with a different type of interaction (Mach or regular). To take into account the real properties of the atmosphere, we used the effective adiabatic exponent method permitting determination of the topology of shockwave patterns and calculation of the gas and thermodynamic parameters in various flow zones between the shock fronts in a wide range of diagnostic variables for the Earth's atmosphere.