METHODS FOR PARALLELIZING MULTIDIMENSIONAL PROBLEMS OF GAS DYNAMICS WITH HEAT CONDUCTION ON THE GRIDS OF MODULAR-MATRIX TYPE

B.L. Voronin, O.I. Butnev, A.N. Bykov, A.M.Erofeev,S.I.Skrypnik, I.D. Sofronov, D. Nilsen
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 3-7.

The paper describes parallelization methods used for developing parallel program implementing Eulerian-Lagrangian technique for numerical solution of 3D time-dependent problems of gas dynamics with heat conduction on the grids of modular-matrix type. Two fundamentally different approaches to arranging array-parallel computations were developed.

       Parallelization efficiency has been numerically studied for various methods of a problem geometrical decomposition, for two modes of processor load and depending on the relation between arithmetic and communication work.

       Parallelization efficiency of the parallel program developed is presented for different high-parallel computer systems.

I.D. Sofronov, S.A. Bel'kov, O.A.Vinokurov, L.S. Mkhitar'yan, N.A. Ryabikina
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

The paper deals with a technique for calculating spectral radiation transport in diffusion approximation in MIMOZA-ND program complex and an implementation of ionization kinetics equation calculation in mean ion approximation.

       2D calculations were performed for asymmetric targets, examined in experiments intended for irradiating X-rays targets on "Iskra-5" plant using the upgraded MIMOZA-ND complex capable of considering time-dependent non-equilibrium spectral transport of X-rays radiation. Computed data were compared with experimental results. It is demonstrated that computed neutron yields and neutron generation time agreed satisfactorily with experimental data.

O.A. Voronova, V.V. Evdokimov, O.A. Zvenigorodskaya, M.S. Samigulin, G.G. Farafontov, R.M.Shagaliev, V.A. Shumilin
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

TENAR program package is described, intended for numerical simulation of nuclear energy plant behaviour under different conditions, from rated duties to emergency ones, with equipment structure preserved.

       The package consists of a program collection, which enables one to simulate processes in the key elements of nuclear energy plants. The package includes the programs allowing the following processes to be taken into account: neutrons transfer and their interaction with medium; delayed neutrons and isotops depletion kinetics; heat-transfer agent flow in a circuit and in nuclear energy plants body; heat conduction in solid elements; thermal mechanics of fuel elements. The package can be supplemented with new components allowing the necessary processes to be considered.

A.V. Alekseev, O.A. Zvenigorodskaya, R.M. Shagaliev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

A brief description is given of an algorithm for parallelizing numerical solution of 3D time-dependent multigroup neutron diffusion equation, implemented in KORAT 3D program.
   The paper presents the results of numerical study of the algorithm considered in the problems of simulating neutron processes in a nuclear power facility on multiprocessors of home and foreign production.

N.M. Rud'ko, S.I.Skrypnik
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

The paper considers a technique for parallelizing numerical solution of 3D equation of heat conduction, in which energy flows are approximated by operators implicit in time on a spatial pattern. The pattern dimension depends on computational grid non-orthogonality degree.
       Some test computations were performed with the program, implementing the above technique. Computed data demonstrated the technique to provide high parallelization efficiency.

O. O. Murugova, Yu. D. Chernyshev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

The paper presents the results of methodical calculations on studying viscosity factor effect on accuracy of computing problems with shock waves of different intensity in the case of ideal gas and a substance with trinomial equation of state. A technique for improving accuracy of computing shock waves is proposed.

A.G. Kozub, O.A. Pronina
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

The fundamental tenets of quasiregular technique for computing gas dynamics processes of multidimensional time--dependent problems are presented. The technique proposed has its origins in regular Eulerian-Lagrangian technique of RAMZES program system and in multigrid method for splitting by spatial directions. The results of methodical calculations demonstrate efficiency of the technique and the programs implementing it.

S.P.Belyaev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

The paper presents the results of studying primary parallel programs development using a parallel program, implementing the technique for computing 3D time-dependent gas dynamics problems in Lagrangian variables as an example. The program implements fine-grained pointwise parallelization, dynamic balance subprogram, subprogram for initial task loading by a single processor to all system processors, collection subprogram and disk record, calculational program, subprogram for selection of a variable step.
      The parallel program was developed on PC under Windows 95 in C++ language. For a "hard" task on the grid as big as 48 x 48 x 48 cells a speedup was 11.561 and a processor application factor - 0.963 at computing on 12 processors. For a "light" task a computation speedup was 10.422 and an application factor - 0.868.

I.D. Sofronov, I.V. Demin, V.A.Novichikhin, L.N. Smirnova, A.A. Solonenkov, S.A. Kholin
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

MIMOZA code was used for computing Zababakhin sloyka (layer cake type) in 16 pairs of heavy and light layers with aspect ratios 0.1 and 0.2 respectively with outer radius 10{cm} and central domain radius 0.0652{cm}. The computations were carried out with/without regard to heat conduction. Parallelization is essential with domain size difference by the factor of 1000. As the basis for paralellization algorithm the authors used a scheme, in which different computational domains were computed on separate processor elements, the values obtained at the previous time step were taken as at the next step. To shorten processors downtime computational domains are rearranged at the end of each step and the order of their computation is changed according to statistics, obtained at the previous step.

A.G. Kozub, O.A.Pronina
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 1. P. 8-15.

Algorithms and programs for global reconstruction of 2D computational grid in RAMZES complex are described. For recalculating grid values unconventional algorithms are proposed based on representation of lines and polygons by their raster scan, used in computer graphics. Specific examples demonstrate serviceability and efficiency of the methods and programs developed.