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RUSSIAN FEDERAL NUCLEAR CENTER 
ALLRUSSIAN RESEARCH INSTITUTE OF EXPERIMENTAL PHYSICS 

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Issue N^{o} 2, 2000  COMPUTATION PARALLELIZATION FOR 2D GAS DYNAMICS PROBLEM ON NONSTRUCTURAL GRIDS ON DISTRIBUTED MEMORY MP3
R. A. Barabanov, O. I. Butnev, S. G. Volkov, B. L. Voronin, B. M. Zhogov, V. A. Pronin, I. D. Sofronov VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 39.
A description is given of an algorithm for parallelizing numerical solution of 2D gasdynamic problems on nonstructural grids for a single mathematical domain on distributed memory computation systems. Difference and finitedifference equations, a method of solving finitedifference equations system, a method of a solution domain decomposition are presented. On distributed memory MP3 computation system a study was made of accuracy of algorithm for numerical solution of 2D problem on RichtmyerMeshkov instability evolution. The estimations of parallelization efficiency on the number of processors up to 8 are given.
 MULTIMESH APPROACH TO THE NUMERICAL SOLUTION OF GASDYNAMIC EQUATIONS BY CHARACTERISTIC DIRECTIONS METHOD WITH TRACKING STRONG AND WEAK DISCONTINUITIES FOR AN ARBITRARY EQUATION OF STATE D. N. Bokov, N. N. Bokov VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 1020.
A concept of a multimesh approach to solving gasdynamic equations with the method of characteristic directions is presented in the paper. A determining system of difference equations for calculating continuous flow is written down in a form of linear combinations of finite increments of conservative variables along the characteristic directions for an arbitrary equation of state. Algorithms are given to calculate the main flow elements: centered rarefaction wave, interface, shock wave and decomposition of arbitrary discontinuity (Riemann problem). The multimesh approach enables development of tools for detailed description of the flow features based on hyperbolic system attributes and tracking interaction between all flow elements. Numerical calculations of the test problems, which prove the high accuracy reached at a small number of grid points are presented.
 ON SOME PROPERTIES OF DSn SCHEMES FOR SPHERICAL SYMMETRICAL TRANSFER EQUATION S.V. Mzhachikh, E.V. Groshev, V.F.Yudintsev VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 2131.
The paper proposes a simple mutual transformation mechanism for divergent and nondivergent difference forms of transfer operator, allowing to present a known DSn method as fourparametrical family of difference schemes and analyze some algorithm for selecting scheme parameters. Numerical calculations on large grids have corroborated high efficiency of this algorithm.
 NUMERICAL SIMULATION OF STRONG LASER PULSESSOLIDS INTERACTION N.V. Bugrov, N.S. Zakharov VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 3241.
The numerical method is developed to calculate the processes of powerful nanosecond laser pulses action on solids with regard to the kinetics of surface vaporization, elasticplastic material properties and electronion exchange effects in laserdriven absorbing plasma. The main laws of the formation of plasma flames and shock waves in targets are determined for different parameters of acting radiation and ambient atmosphere.
 SIMULATION OF ENERGY RELEASE AREA AT HEATING MAGNETIC PLASMA UNDER ELECTRONCYCLOTRON RESONANCE CONDITIONS S.V. Danilov, A.E. Dubinov, V.D. Selemir VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 4248.
A technique is described for computing structure of energy release area at heating magnetic plasma under electroncyclotron resonance conditions. The program, implementing this technique, allows studying the focal distance influence for input of the heating superhighfrequency generator rays. The numerical simulation data, obtained through the use of the above technique, are presented.
 C95 PROGRAM. SIMULATING JOINT TRANSFER OF NEUTRONS AND LARGE gammaRAY QUANTA USING MONTE CARLO METHOD Yu. K. Kochubey, A. K. Zhitnik, E. V. Artem'eva, E. N. Donskoy, V. A. Eltsov, N. V. Ivanov, A. N. Ivanov, A. A. Kibkalo, A. I. Morenko, L. Z. Morenko, S. P. Ognev, A. B. Ronzhin, V. I. Roslov, T. V. Semenova, A. N. Subbotin, E. L. Trushchina VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 4952.
A description of C95 program is given. It is a new version of the program intended for joint solution of the neutrons and gammaray quanta transfer equations using Monte Carlo method. The program can be used on PCs and multiprocessors.
 ORGANIC LIQUIDS MIGRATION IN SEAMYPOROUS ZONE OF AERATION A.V. Kosterin, V.I. Selin VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 5357.
A mathematical model of organic liquids migration in aeration seamyporous zone is described. An analytical solution of a problem in a model formulation is obtained, which can be used for testing numerical techniques as well as for obtaining practical estimations of qualitative character for aeration zone pollution.
 ABOUT MECHANISM OF CAVITY FORMATION INSIDE A BALL UNDER ITS EXTERNAL SHOCK LOADING V.Yu. Meltsas, V.N. Rodigin VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 5862.
A model using acoustic approximation to describe a shock wave converging to the centre and the one reflected from it in a ball is proposed. The model takes into account the possibility of unrestricted cumulation converging to the wave centre. Within the model the interference of the incident wave and of the wave reflected from the center is demonstrated to result in their "selfextinction". In response to it, immediately after the incident wave front focusing a restricted and constant uniform material tension is established close to the centre for the period of the wave action. In this situation, when material strength is sufficient enough, no cavity is formed in a ball. Otherwise the cavity can be formed, which is in qualitative agreement with known experiments. A numerical example is offered, showing that in the case of incident wave front smearing, when the wave is brought into focus, cumulation can not be infinite.
 SINARA SOFTWARE PACKAGE FOR NUMERICAL SIMULATION OF EMERGENCY PROCESS DYNAMICS IN FAST REACTORS V. V. Gadzhieva, N. V. Gorin, A. V. Kim, S. Yu. Kuzmin, S. N. Lebedev, T. V. Lebedeva, G.V. Orlov, V. N. Pisarev, N. V. Ptitsyna, E.M. Romanova, V. V. Rykovanova, O. V. Stryakhnina, E. A. Sozinov, A. A. Shestakov, V. M. Shmakov VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 6373.
The paper describes a software package SINARA for calculating some emergency processes in a fast reactor. The movement of multicomponent onespeed medium is simulated. Account is taken of elastic and strength properties of materials, linear heat conduction, neutron transport in kinetic and diffusion approximations, nuclei kinetics, energy release, delayed neutrons. The medium model gives consideration for elasticity, plasticity, compressibility, destruction, fusion, evaporation and multicomponent nature. The finitedifference methods for calculating gas dynamics movement and thermal processes are based on implicit ROMB technique, those for calculating kinetic processes  on diamond model of Dsnmethod. The calculations of core emergency energy release effect on reactor vessel were carried out. Base tools for arranging parallel computations on various types of computers were created. For parallelizing calculations a geometrical decomposition method with the introduction of internal boundary conditions was applied.
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