Since 1978
Published in Sarov (Arzamas-16), Nizhegorodskaya oblast

RUSSIAN FEDERAL
NUCLEAR CENTER -
ALL-RUSSIAN RESEARCH INSTITUTE
OF EXPERIMENTAL PHYSICS
 
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Issue No 4, 2017

DATA STRUCTURE OF "TIM" METHOD TO SOLVE 2D AND 3D PROBLEMS OF CONTINUUM MECHANICS

A. A. Voropinov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 3-13.

A static polumorphism-based approach to data structure organization using inheriting mechanisms of Fortran 2003 programming language is discussed. The advantage of the approach described is the possibility of simultaneous implementation of both the old structures that do not use inheriting mechanisms and new ones through the structures with polymorphism.
The described approach is used in the program realization of the data structures of TIM method designed for solution of 2D and 3D problems of continuum mechanics on non-structured Lagrangian grids. Implementation of static polymorphism made it possible to realize a unified data structure for 2D abd 3D cases.


Key words: non-structured grid, data structure, polymorphism, Fortran 2003.

A 2D MODEL OF LASER RADIATION PROPAGATION AND ABSORPTION IN ICF TARGETS WITH THE ACCOUNT FOR REFRACTION

A. V. Vronsky, M. N. Chizhkov, A. A. Shestakov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 14-24.

A 2D model is presented for laser radiation transfer and absorption in axisymmetric medium with the account for deflection and reflection of laser beams in geometrical optics approximation. Two approaches are considered. The density and the temperature of the electrons inside the counting cell are considered constant in the first approach, and the light beam trajectory inside the cell is a straight line. At the boundary between the cells with different cells there is either deflection or reflection of the beam in compliance with the laws of geometrical optics. At the second approach gradients of the density and temperature of electrons inside the cell are presumed to be constant and the trajectory of the beam in the cell has a parabolic shape. Additional correction of the beam direction is done at the cell boundary if necessary. There are test results for the proposed model done with the problems that have exact solution.


Key words: laser radiation transfer, refraction.

ON ONE BENCHMARK PROBLEM OF LAYERED STRUCTURE COMPRESSION WITH THE ACCOUNT FOR RADIATION TRANSFER IN DIFFERENT APPROXIMATIONS

A. A. Shestakov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 25-31.

A benchmark problem was offered that simulates compression of the simplest layered structure of two materials. The main distinctive features of the test are as follows:
1) a unified setting of the boundary and initial conditions of the radiation transfer in different approximations in 1D, 2D and 3D geometries;
2) simple analytical formulas for spectral paths that make it possible to do calculations in one-group and multi-group setups;
3) a wide variation range for the spectral absorption factor;
4) the simplest equations of state.
The calculation results are given in five approximations: kinetic, diffusion, quasi-diffusion, P1approximation in one-group and multi-group setups, as well as in the approximation of radiating thermal conductivity.


Key words: radiation transfer, compression of the layered system.

TFS METHOD. ITS TESTING ON STATIONARY 1D TRANSFER PROBLEMS

V. V. Evdokimov, I. A. Nizamova
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 32-47.

An approach to the scheme construction to solve the equation of transfer in kinetic approximation is offered. An approach to the scheme design to solve a transfer equation in kinetic approximation is described. An approximation scheme allowing explicitly express unknown values of the particles at the outlet from the cell is taken as the basic one. Then the cells are symbolically subdivided into sub-cells and the solution as a function of initial and boundary conditions is obtained for each sub-cell in series. The sum of all outgoing fluxes produces the expression for the flux at the output from the initial cell. The size of sub-cells is selected in such a way that the condition of positive approximation scheme is met. The number of sub-cells can strive to infinity; in this case we have a limit option of the scheme. The suggested approach to the scheme construction is called a TFS-method.
Implementation of a TFS-method is considered for designing the scheme to solve the equation of neutron transfer in 1D stationary case. The computation results of two 1D stationary problems using a new scheme are given and they are compared with the results produced by known DD- and St-schemes.


Key words: TFS-method, transfer equation, difference schemes, testing, stationary transfer problems, DD-scheme, St-scheme, Reed test.

MANAGEMENT SYSTEM FOR THE COMPUTATIONAL NODES OF THE MULTIPROCESSOR COMPLEX ON THE BASIS OF THE PROTOCOL OF THE CONCURRENT PROCESSING OF THE REMOTE COMMANDS

E. V. Eremin, N. N. Zalialov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 48-60.

Management system for computational nodes of a multiprocessor complex based on the original protocol of the concurrent processing of the remote commands is described. The description of the protocol is provided as well as the set of the commands for the remote access to the computational nodes. Traditional means of the remote access such as SSH or PDSH perform the inquest to n nodes successively that has asymptotic complexity O (n). It is possible to reduce the complexity down to O (log n) using a so-called inquest tree a way to separate the initial set of nodes into parts and work with them at the same time. The results of the command performance are grouped to reduce the volume of data and for the convenience of their analysis. Internal handlers of some commands of UNIX/Linux operating system are realized (cat, grep, ls, ps etc.), that allow eliminating overheads of process recreation, memory allotment etc.


Key words: management, protocol, concurrent processing, client, server, inquest tree, command line utility, remote access, remote procedure call.

SREDA3D SERVICE SYSTEM TO FORM INITIAL DATA WHEN RECALCULATION MESH VALUES FROM ONE REGULAR MESH INTO ANOTHER

Emelianov A. B.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2017. No 4. P. 61-67.

Sreda3D service system created in RFNC-VNIIEF is one the technology components of global re-gridding and re-computation of values from one regular grid to another. It is designed to form initial data (initial geometry and computational grid) when doing numerical solution of continuum mechanics problems using such methods as RAMZES-KP, KORONA, and . The work describes functional capabilities of Sreda3D system and shows the stages of the initial data preparation for the problem on the basis of a regular mesh.


Key words: re-gridding, recalculations of mesh values, graphic users interface, initial mesh data, cutset-source, cutset-receiver, regular leaf-like mesh, EFR library, EFR format.

 
 
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