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RUSSIAN FEDERAL
NUCLEAR CENTER -
ALL-RUSSIAN RESEARCH INSTITUTE
OF EXPERIMENTAL PHYSICS
 
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Issue No 2, 2018

"NIMFA" SOFTWARE COMPLEX FOR SOLVING PROBLEMS OF NONLINEAR SINGLE-PHASE FLUID FLOWS AND HEAT-AND-MASS TRANSPORT IN POROUS MEDIA

O. I. Butnev, M. L. Glinskii, I. V. Gorev, A. A. Kuvaev, P.A. Mashen'kin, V. A. Pronin, M. E. Semyonov, M. L. Sidorov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 3-14.

The paper describes NIMFA software complex and techniques used to solve the single-phase fluid flow and heat-and-mass transport problems in porous media. The principal equations of the simulated processes and grids in use are presented. The qualitative and quantitative agreement between the results obtained for the problems having exact solutions and those solved using other program complexes is demonstrated.


Key words: NIMFA software complex, single-phase flow model, heat-and-mass transport.

NUMERICAL SOLUTION OF THE 2D RADIATIVE HEAT TRANSFER EQUATION USING SPH METHOD

A. A. Lazarev, S. N. Polischuk, B. P. Tikhomirov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 15-24.

The numerical solution of the 2D radiative heat transfer equation using smoothed-particle hydrodynamics (SPH) is considered. The difference approximation to the equation is given for the planar and axially symmetric problems. The equation discretization is performed using an implicit difference scheme with further linearization of the equation according to Newton. For problems with axial symmetry, the paper offers the method of calculations in the vicinity of rotation axis, which is based on the use of a planar interpolation kernel and auxiliary (fictitious) particles. A simple algorithm of simulating boundary conditions is given. Simulation results are presented for some test problems having known exact solutions.


Key words: radiative heat transfer equation, smoothed-particle hydrodynamics (SPH), implicit difference scheme, uniform and chaotic arrangement of particles, test simulations.

AN AUTOMATIC GENERATOR OF UNSTRUCTURED POLYHEDRAL GRIDS IN THE "LOGOS" SOFTWARE PREPROCESSOR

D. N. Smolkina, O. N. Borisenko, M. V. Cherenkova, A. G. Giniyatullina, M. V. Kuz'menko, N. V. Chukhmanov, E. V. Potekhina, N. V. Popova, M. R. Turusov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 25-39.

The paper describes an automatic generator of unstructured grids used to solve problems of aero- and hydromechanics implemented in LOGOS software complex. Stages of generating a 3D grid are considered, an example of the stage-by-stage construction of a grid is given.


Key words: LOGOS software complex, preprocessor, unstructured grids, a refined grid, grid quality improvement.

BUILDING A 3D GRID BASED ON THE VORONOY DIAGRAM IN NONCONVEX REGIONS

A. A. Voropinov, S. S. Sokolov, A. K. Shmelyova
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 40-54.

For numerically solving 3D continuum mechanics problems in regions of complex geometry, the geometric model of a structure is often set as a surface grid and boundary conditions are formulated to describe the impact on the system. One of the important tasks is to build a high-quality computational grid, especially near the structures boundaries.
The paper describes an approach to building a 3D unstructured grid based on the Voronoy diagram with a special arrangement of the grid cell centers near the original surface grid followed by removal of the outer layer of cells. Such approach to the arrangement of centers allows constructing grids in nonconvex regions. Algorithms are implemented in the TIM code.


Key words: TIM code, an unstructured grid, 3D Voronoy diagram, a grid based on the 3D Voronoy diagram, initial data calculation, a surface grid.

THE ALIAS METHOD FOR SIMULATING DISTRIBUTION TABLES OF RANDOM VARIABLES

A. N. Zalyalov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 55-61.

The paper considers the Alias method of simulating distribution tables of random variables. The original algorithm of preprocessing tables is described. Formulas are given for the simulation of multidimensional tabular distributions: discrete, piecewise linear, and piecewise constant (specified either by a histogram, or as a fraction of particles within each range of values) distributions.


Key words: random variable, Alias method, distribution tables, the Monte Carlo method.

SIMULATION OF THE HUMAN THERMAL COMFORT BYlb MEANS OF "LOGOS" SOFTWARE COMPLEX

N. G. Galanov, R. N. Zhuchkov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 62-71.

The paper gives the main definitions and equations of the human thermal comfort model, as well as the specific features of its implementation in LOGOS software complex. An example of solving a typical problem is considered. Simulation results are compared with data of experiments.


Key words: LOGOS software complex, thermal comfort model, index of subjective sensations, discomfort ratio.

A PARALLEL DEBUGGER FOR CLUSTERS ON THE BASE OF OS LINUX

A. B. Kiselyov, S. N. Kiselyov, G. P. Semyonov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2018. No 2. P. 72-81.

The paper presents a debugger for parallel programs in C/C++, or FORTRAN, which are executed on distributed-memory computers. The debugger's program components and mechanism of their interaction are described. The graphic user's interface capabilities are discussed and the profiling procedure using builtin profiling tools is described.


Key words: multiprocessor computing system, interactive debugging, parallel program debugging.

 
 
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