COMPUTATION PARALLELIZATION FOR 2-D GAS DYNAMICS PROBLEM ON NONSTRUCTURAL GRIDS ON DISTRIBUTED MEMORY MP-3

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. 3-9.

A description is given of an algorithm for parallelizing numerical solution of 2-D gas-dynamic problems on nonstructural grids for a single mathematical domain on distributed memory computation systems. Difference and finite-difference equations, a method of solving finite-difference equations system, a method of a solution domain decomposition are presented.
   On distributed memory MP-3 computation system a study was made of accuracy of algorithm for numerical solution of 2-D problem on Richtmyer-Meshkov instability evolution. The estimations of parallelization efficiency on the number of processors up to 8 are given.

D. N. Bokov, N. N. Bokov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 10-20.

A concept of a multimesh approach to solving gas-dynamic 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.

S.V. Mzhachikh, E.V. Groshev, V.F.Yudintsev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 21-31.

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 four-parametrical family of difference schemes and analyze some algorithm for selecting scheme parameters. Numerical calculations on large grids have corroborated high efficiency of this algorithm.

N.V. Bugrov, N.S. Zakharov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 32-41.

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, elastic-plastic material properties and electron-ion exchange effects in laser-driven 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.

S.V. Danilov, A.E. Dubinov, V.D. Selemir
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 42-48.

A technique is described for computing structure of energy release area at heating magnetic plasma under electron-cyclotron resonance conditions. The program, implementing this technique, allows studying the focal distance influence for input of the heating superhigh-frequency generator rays. The numerical simulation data, obtained through the use of the above technique, are presented.

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. 49-52.

A description of C-95 program is given. It is a new version of the program intended for joint solution of the neutrons and gamma-ray quanta transfer equations using Monte Carlo method. The program can be used on PCs and multiprocessors.

A.V. Kosterin, V.I. Selin
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 53-57.

A mathematical model of organic liquids migration in aeration seamy-porous 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.

V.Yu. Meltsas, V.N. Rodigin
VANT. Ser.: Mat. Mod. Fiz. Proc. 2000. No 2. P. 58-62.

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 "self--extinction". 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.

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. 63-73.

The paper describes a software package SINARA for calculating some emergency processes in a fast reactor. The movement of multicomponent one-speed 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 finite-difference methods for calculating gas dynamics movement and thermal processes are based on implicit ROMB technique, those for calculating kinetic processes - on diamond model of Dsn-method. 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.