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RUSSIAN FEDERAL NUCLEAR CENTER 
ALLRUSSIAN RESEARCH INSTITUTE OF EXPERIMENTAL PHYSICS 

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Issue N^{o} 4, 2003  NONUNIQUENESS OF RAREFACTION SHOCK WAVES: EFFECT OF VISCOSITY AND DISPERSION
Yu. A. Bondarenko, V. N. Sofronov, V. P. Kopyshev, V. V. Khrustalev VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 312.
A study is made for automodel solutions of Riemann problem for substances with nonconvex strictly monotonous equation of state, in which rarefaction shock waves arise at unloading. Available data on rarefaction shock waves properties are based on the assumption that any discontinuous solutions of gasdynamic equations are to be derived from smooth solutions of gasdynamic equations with viscosity through limiting passage to an infinitesimal coefficient of viscosity. In this paper for smooth nonconvex barotropic equations of state properties of rarefaction shock waves are obtained by analytical study for another method of gasdynamic equations regularization that is for the one using artificial normal dispersion. The parameters of rarefaction shock waves gained with a method of disappearing normal dispersion are proved to differ from those gained with a method of disappearing viscosity. Analytical data are confirmed by onedimensional gasdynamic calculations using differential schemes with controlled dissipation and dispersion. The obtained results enable one to conclude that problem of choosing unique and “proper” rarefaction shock wave in gasdynamic calculations should be solved at a level with physical models choice and depends on main physical processes, which are to be thrown away when writing equations of ideal gas dynamics.
 DISCRETE ORDINATE METHOD WITH ARTIFICIAL DISSIPATION (DDADSCHEME) FOR NUMERICAL SOLUTION OF NEUTRON TRANSPORT EQUATION A. D. Gadzhiev, I. A. Kondakov, V. N. Pisarev, O. I. Starodumov, A. A. Shestakov VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 1324.
A study is made of discrete ordinate method with artificial dissipation (DDADscheme) for solving numerically neutron transport equation in one and twodimensional geometries. An artificial dissipation is introduced to weaken nonphysical oscillations, appearing when solving transport equation in optically dense media with discrete ordinate method of the second order of accuracy.
 INCLUSION OF MEDIUM ATOMS MOTION IN SOLVING PROBLEMS OF NEUTRON TRANSPORT USING MONTECARLO METHOD A. N. Ivanov, N. V. Ivanov VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 2532.
The problem of taking account of thermal medium atom motion in MonteCarlo method is considered. Effective schemes of modeling neutrons paths based on preliminary calculated thermal sections for base temperature are presented.
 DS_{n}METHOD WITH ARTIFICIAL DISSIPATION AND DMSMETHOD OF ITERATION ACCELERATION FOR NUMERICAL SOLUTION OF 2D EQUATION OF HEAT RADIATION TRANSPORT IN KINETIC MODEL A. D. Gadzhiev, V. N. Seleznev, A. A. Shestakov VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 3346.
A numerical algorithm for solving 2D equations of heat radiation transport in multigroup kinetic approximation is studied. The algorithm is based on DDADscheme, which is a scheme of DS_{n}method with artificial dissipation. A method of diagonal matrix segregation (DMSmethod) is used to accelerate iterations in solving a transport equations set. The computational data for two model problems are presented.
 EXPERIMENTAL AND NUMERICAL (MULTIPROCESSOR) STUDY OF COATING STABILIZING ACTION ON DEVELOPMENT OF SHEAR INSTABILITY IN METALS S. M. Bakhrakh, N. A. Volodina, O. B. Drennov, T. A. Goreva, A. L. Mikhaylov, P. N. Nizovtsev, E. V. Shuvalova VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 4754.
The paper presents the results of numerical simulation of the media interface coating effect on the process of shear instability development under oblique collision of metal plates. The state of materials is described in elasticplastic approximation. A study is made of disturbance amplitude dependence on coating thickness and features. Computations were carried out on multiprocessor distributedmemory system.
 MADS++ CODE FOR CALCULATION OF CONTINUUM MECHANICS PROBLEMS ON ADAPTIVELYEMBEDDED GRID A. V. Babanov, V. V. Zmushko, P. V. Rybachenko, A. E. Bolshakova VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 5560.
To study the opportunity and efficiency of using method of adaptively embedded grids in numerical simulation of physical processes a methodical code MADS++ is developed. Some test calculations were carried out with the code to simulate numerically detonation processes, elasticplastic flows and gas dynamics. The computational results, obtained with MADS++ code were compared with those, obtained earlier with the codes of MIMOZA complex, and experimental data.
 3D SIMULATION OF GAS FLOW BY PIC CODE WITH AMR TECHNIQUE. COMPUTATION OF SEDOV`S IMPLOSION PROBLEM O. N. Pavlenko, I. A. Litvinenko VANT. Ser.: Mat. Mod. Fiz. Proc.. 2003. No 4. P. 6167.
The original particleincell method (PIC) with ARM technique for 3D simulation of gas flow with severe deformations is given. Numerical algorithm is described. Sedov’s problem simulation results are presented. The analysis of numerical solution showed the capacity of ARM technique to describe the shock motion from an explosion region which is 200 times smaller than a computational one. The spherical nature of solution remains despite of cube grid. A good agreement with analytic solution is demonstrated. The paper presents computational results for an interaction of a spherical wave generated by a point explosion with a dense spherical body. 3D simulation are in good agreement with 2D PIC simulations.
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