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RUSSIAN FEDERAL NUCLEAR CENTER 
ALLRUSSIAN RESEARCH INSTITUTE OF EXPERIMENTAL PHYSICS 

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Issue N^{o} 4, 2001  COMPARATIVE COMPUTATIONS OF ONE 3D TIMEDEPENDENT TEST PROBLEM FOR THE REACTOR RBMK WITH THE CODES KORAT3D, DINA, STEPAN AND Z3DAM (ACADEM)
O. A. Zvenigorodskaya, R. M. Shagaliev, T. V. Shemyakina, E. N. Danilova, L. N. Podlazov, N. L. Chichulin, A. V. Krayushkin, Yu. A. Tishkin, S. M. Tsareva, A. I. Zinin, V. A. Pivovarov VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 310.
The verification of neutronphysics program forming a part of fullscale complexes intended for analyzing dynamics and safety of reactors requires a benchmark database. A description of one of these benchmarks, namely, 3D timedependent test problem is given. The results of its diffusive computations obtained with the codes KORAT3D, DINA, STEPAN are analyzed. The computational data for conditionally critical problems gained using the above codes and the stationary code Z3DAM are presented.
 THE IMPLICIT FINITEDIFFERENCE METHOD ROMB FOR SOLVING 2D GASDYNAMIC EQUATIONS A.D. Gadzhiev, S.Yu. Kuzmin, S.N. Lebedev, V.N. Pisarev VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 1121.
The implicit finitedifference method ROMB for numerical solution of 2D gasdynamic equations is presented. The method is based on the use of arbitrary LagrangianEulerian quadrangle grids. The scheme is unconditionally stable and allows simulating the currents of both almost non compressible and strong compressible medium. The "diamond" approximations are simple and provide the satisfactory accuracy for highly deformed nonorthogonal grids. The scheme of the ROMB technique is conservative (a complete conservatism easy to achieve with respect) to energy equation. For 2D difference equations system solution the economical iterative method with stabilizing correction is used. The examples of calculations are given.
 THE STUDY OF ROMB SCHEME FOR SOLVING 2D GASDYNAMIC EQUATIONS WITH THE METHOD OF APRIORI ESTIMATES A.D. Gadzhiev, S.Yu. Kuzmin VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 2229.
A theoretical investigation of the implicit finitedifference method ROMB for numerical solution of gasdynamic equations is carried out. A study is made of an approximation error which turns out to be the error of the second order of smallness, both on irregular and nonorthogonal grids. The scheme steadiness for initial data, right side and boundary conditions is proved by the method of energetic inequalities. A proof is given for the method convergence in a form of apriori estimates.
 NUMERICAL SIMULATION OF INITIAL PERTURBATION GROWTH IN OBLIQUE IMPACT OF METAL PLATES S. M. Bakhrakh, N. A. Volodina, P. N. Nizovtsev, V.F. Spiridonov, E. V. Shuvalova VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 3034.
A direct numerical simulation is performed for initial perturbation growth in oblique impact of metal plates. The results agree with relevant experimental data. It is confirmed numerically that under experimental conditions the perturbations of wavelength l=0,5 mm grow most intensively. The numerical simulation revealed a number of new effects.
 AN ADDITIONAL INTEGRAL EQUATION OF RADIATION TRANSFER Yu. A. Dement'ev, E. A. Karpovtsev, E. V. Morozova, I.A. Narozhnaya, V. A. Novichikhin, E. N. Tikhomirova, E. I. Ryabov VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 3541.
The techniques for numerical solution of radiation transfer problems based on the approximation of linear transfer equations used these equations in one of two forms: integrodifferential and integral. A new transfer equation is derived from an integrodifferential one as a wellknown integral transfer equation but with additional geometrical and optical elements. Therefore a new transfer equation is called an additional integral equation of transfer. For a fixed point source this equation describes the distribution of straightshot quanta energy on a boundary surface and the distribution of the energy removed by a substance within a transfer domain volume. The new equation allows the construction of explicit conservative numerical schemes with sequential independent description of transfer from each grid source.
 A SPECTRAL RADIATION TRANSFER SIMULATION WITH MONTECARLO METHOD IN A PARALLEL COMPUTATION MODE A.A. Kibkalo, L.Z. Morenko VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 4247.
An algorithm for parallelizing a program for simulation of nonlinear spectral radiation transfer on gasdynamic crosssection with MonteCarlo method is described. Parallelization efficiency estimates are obtained for different number of processors on multiprocessing complex. The characteristics of parallelizing the code to solve the problem of symmetrization of radiation flow to the thermonuclear target are presented.
 TOM4KD TECHNIQUE FOR COMPUTATIONAL SIMULATING 2D EQUATIONS OF RADIATION TRANSFER IN MULTIGROUP QUASIDIFFUSIVE APPROXIMATION A.D. Gadzhiev, E.M. Romanova, V.N. Seleznev, A.A. Shestakov VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 4859.
The solution of 2D equations of radiation transfer in multigroup quasidiffusive approximation with the difference scheme ROMB is considered. P_{1}corrections method is used to accelerate iterations when solving the system of quasidiffusive equations. Correction equations are solved by a diagonal element selection method.
 THE PARALLELIZATION OF EXPLICITLY IMPLICIT ALGORITHM FOR GASDYNAMIC CALCULATIONS ON MULTIPROCESSING SYSTEMS WITH DISTRIBUTED MEMORY S. M. Bakhrakh, S. V. Velichko, O. N. Zhivechkova, M. V. Luchinin, V. F. Spiridonov VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 6064.
An explicitly implicit algorithm for pressure calculation used to compute problems on computers with distributed memory. The data computed in multiprocessor mode confirm the serviceability of a parallelized program algorithm as well as the acceptable and theoretically expected efficiency of parallelization.
 THE SERVICE PROGRAMS PACKAGE FOR 3D PARALLEL COMPLEX D V.I. Budnikov, D.M. Linnik VANT. Ser.: Mat. Mod. Fiz. Proc. 2001. No 4. P. 6568.
The serviceprograms package for 3D parallel complex D is described. This complex is demonstrated to be divided into two parts: computational and service. Computational part can operate on both computer complex in a parallel mode and PC in a serial one. The service part is only implemented for PC and serves for data processing, visualization and analysis as well as for performing necessary manual operations during calculations.
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