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RUSSIAN FEDERAL NUCLEAR CENTER 
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Issue N^{o} 4, 2020  USE OF HAMILTONIAN DYNAMICS METHODS IN COMPUTATIONAL CONTINUUM MECHANICS
V. N. Sofronov, M. V. Vetchinnikov, M. A. Dyemina VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 521.
The paper presents a computational continuum mechanics method based on discrete Hamiltonian dynamics. Hamilton’s equations are numerically solved using symplectic difference schemes. Examples of dissipationfree process simulations are provided. Key words: discrete Hamiltonian dynamics, phase volume, symplectic difference schemes, dynamic elasticity problems, MoDyS software package.
 EULERIAN MULTIPHASE FLOW SIMULATIONS BASED ON THE "SIMPLE" METHOD O. G. Bliznyuk, O. E. Vlasova, A. V. Gichuk, A. S. Kozelkov, I. V. Lyalyushkina VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 2232.
Specific details of using the SIMPLE method for multiphase flow simulations involving phase interactions are described. A multifluid model is used, in which each phase has its own density, velocity and temperature. Results of some test simulations are reported for the algorithm implemented in the software package "Logos". Key words: multiphase flow, numerical simulations, SIMPLE method, "Logos" software package.
 "LOGOS" SOFTWARE PACKAGE. INCORPORATION OF CONTACT INTERACTIONS IN QUASISTATIC DEFORMATION SIMULATIONS A. Yu. Eryemenko, S. S. Kosarim VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 3347.
Details of incorporating contact interactions between different bodies or structural components in quasistatic deformation simulations by the "Logos" software package are discussed. As a basic method for this, a penalty method has been chosen. An algorithm is described, which detects interpenetration of bodies in contact. Basic formulas for contact forces and their contributions to the global stiffness matrix are given. A separate description is provided for the way to incorporate friction between bodies in contact. The accuracy of the implemented methods is illustrated by numerical simulations of the Hertz contact problem with friction between two infinitely long cylinders and by comparison of these simulations with the analytical solution. Key words: quasistatic deformation, incorporation of contact interactions, penalty method, penetration detection algorithm, incorporation of friction, Hertz contact problem, "Logos" software package.
 TEST PROGRAM "PAUK" AS A TESTING RANGE FOR PARALLEL PROGRAMMING ALGORITHMS AND TECHNIQUES A. A. Nuzhdin VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 4861.
PAUK is a test program that numerically solves the threedimensional onegroup neutron transport equation on orthogonal spatial grids by the difference S_{n}method. The paper presents the results of its adaptation for a heterogeneous computing system with Intel’s Knights Corner Xeon Phi coprocessors. The adaptation included testing of various parallel programming algorithms and techniques, namely loop vectorization in directions and hyperplane elements, automatic vectorization and intrinsic programming, explicit and implicit data prefetching, implementation of the KBA algorithm in three memory models (shared, distributed, PGAS). Adaptation efficiency was verified by program performance studies in various execution modes at the heterogeneous computing system: CPUonly, native and symmetric. Key words: S_{n}method, sweep algorithm, KBA algorithm, Intel Xeon Phi, vectorization, data prefetching, MPI3 SHM.
 AN EFFICIENT ALGORITHM FOR MERGING NODEMATCHED FRAGMENTS OF SURFACE GRIDS V. V. Lazarev VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 6271.
A new algorithm is proposed for merging nodematched fragments of surface grids constructed based on a geometric model in the BREP representation. As opposed to classical merging algorithms, this algorithm: 1) considers groups of nodes rather than each individual node; 2) identifies matching nodes based on the connections between grid fragments, which are stored in geometric model representation structures, rather than based on the distance function and its minimum value; 3) instead of storing the result of merging in arrays, represents it in the form of functions, which calculate the node address in the grid fragment based on the node index and the node indexes in a cell, based on the cell index. The processor time and the memory consumed by the algorithm are negligibly small. They depend only on the number of grid fragments and do not depend on the number of nodes or cells in the fragments. Key words: composite grid, surface grid merging algorithm, global indexing, functional representation of a set, boundary representation of a geometric model (BREP).
 AN UNSTRUCTURED QUADRILATERAL SURFACE grid GENERATOR IN THE PREPROCESSOR OF THE "LOGOS" SOFTWARE PACKAGE E. Yu. Arapova, V. G. Kudelkin, E. A. Pavlov, S. Yu. Polyakova, A. V. Tikhonov VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 7285.
The paper describes an automatic generator of unstructured quadrilateral surface grids for geometric models in the parametric representation. The grid generator is intended to construct grid models for strength simulations in the "Logos" software package. Steps of the surface grid generation procedure are considered. One of the steps, namely generation of quadrilateral grids in the parametric plane, is discussed in detail. Examples of test problems with different geometric models are given. Key words: "Logos" software package, quadrilateral surface grids, moving front, generation of quadrilateral cells, local smoothing, topological optimization.
 ON THE DEVELOPMENT OF A GRID GENERATION ALGORITHM FOR DEFORMED SOLIDS OF REVOLUTION FORMED BY SEVERAL SURFACES N. A. Artyomova, O. V. Ushakova VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 4. P. 8696.
A problem of grid generation in solids of revolution deformed by solids of revolution is under consideration. The solid of revolution can be generated by cylindrical, conical or spherical surfaces and formed by rotating two types of elements  segments of straight lines and arcs of circles. A nonstationary algorithm of grid generation in the domains with moving deforming boundaries has been offered earlier for special cases of deformation by a cylinder, a cone and a sphere. This work describes an extension of this nonstationary algorithm. The idea of the algorithm is the same, but its implementation has become more complicated as a result of the increased structural complexity of the deforming domain. Some examples of grids are provided. Key words: structured grids, domain of revolution, deformed domain of revolution, optimal grids, moving grids.
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