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Issue No 3, 2020


IDENTIFICATION OF THE "LOCAL" HOMOGENEOUS MIXING DEGREE IN THE DIRECT NUMERICAL SIMULATION OF TURBULENT MIXING

Yu. V. Yanilkin, A. R. Guzhova, L. I. Degtyarenko, O. G. Sinkova
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 3-10.

The paper describes a model used to identify the local (in space) degree of homogeneous mixing in the direct numerical simulation of the turbulent mixing of two immiscible fluids. The term "local" means that the degree of homogeneous mixing is identified for each mixed cell containing two materials. The model is based on the analysis of a mixed cell from viewpoint of the ability to reconstruct a material-material interface in such a cell. If the interface is recoverable, it is assumed that materials are not mixed in the cell, otherwise materials are in the mixed state.
The model was tested on the classic problem of turbulent mixing under the Rayleigh-Taylor instability conditions due to a continuously accelerating interface between two fluids (gases) of different densities. Both the 2D and 3D numerical simulations of the problem were performed. Results of simulations with the proposed model for the integral (in space) degree of homogeneity were compared with those obtained using the known model. There is a satisfactory agreement of results that allows stating the proposed model adequacy.


Key words: Rayleigh-Taylor instability, turbulent mixing area, direct numerical simulation, a homogeneous mixing degree, the EGAK code.
3D SIMULATION RESULTS FOR CONVERSION OF LASER RADIATION TO X-RAY RADIATION IN A SPHERICAL HOHLRAUM UNDER THE MEGAJOULE LASER FACILITY CONDITIONS

S. V. Bondarenko, E. I. Mitrofanov, L. F. Potapkina, O. O. Sharov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 11-22.

The paper presents results of one-dimensional (using the SNDP code) and three-dimensional (using the MIMOZA-ND3D code) simulations of the laser radiation conversion to X-rays for compressing capsules with a plastic (CH) ablator and an ablator made of high-density carbon (HDC).
The laser facility for irradiating a spherical hohlraum has a full system of cube symmetries (6 inlet openings to deliver radiation to the hohlraum). On the assumption of such conditions and symmetry of the target itself it is suggested to perform 3D simulations for a 1/48 part of the target, this allows significantly decreasing the computational burden.
The 3D simulation has demonstrated that an essential part of the delivered laser radiation is absorbed in the interior space of the hohlraum near the inlet openings, in plasma "evaporated" due to radiation from the hohlraum walls.


Key words: indirect irradiation of a target, a spherical hohlraum, laser radiation, X-ray radiation, plastic (CH) ablator, HDC-ablator.
A METHOD FOR AUTOMATIC GENERATION OF SURFACE GRIDS ON FACES OF GEOMETRIC MODELS IN PARAMETRIC REPRESENTATION IN THE "LOGOS" SOFTWARE PACKAGE PREPROCESSOR

A. P. Bespalov, D. V. Loginov, A. N. Solovev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 23-39.

The paper describes a method of automatically generating surface quadrangular (fully, or predominantly) grids for geometric models in parametric representation. The method has been implemented in the "Logos" software package and is used to solve the strength analysis problems. The key aspects and logic of the surface grid generating algorithms in the "Logos Prepost" preprocessor are considered.


Key words: the "Logos" software package, solution of strength analysis problems, preprocessor, generator of surface quadrangular grids, moving front, block-structured grids, B-REP.
ALGORITHMS OF PREPROCESSING SINGULARITIES IN GEOMETRIC MODELS TO GENERATE SURFACE TRIANGULAR GRIDS IN THE "LOGOS" SOFTWARE PACKAGE PREPROCESSOR

O. N. Borisenko, A. N. Lukichev, A. O. Evstifeeva, D. M. Pankratov, T. V. Tsalko, A. G. Giniyatullina
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 40-52.

The description of algorithms for preprocessing the geometric model singularities in the boundary representation (B-REP) which have been implemented in the automatic generator of surface triangular grids is presented. The generator is intended for constructing grid models to solve aerohydrodynamics problems using the "Logos" software package. The surface grid optimization algorithms implemented to lower the original geometry quality requirements are considered.


Key words: the "Logos" software package, preprocessor, generator of a surface triangular grid, B-REP, geometric singularities, partition of the geometric model edges, contour of a face, surface curvature, closure of contours.
A BLOCK-STRUCTURED GRID WITH BLOCKS HAVING PARTIALLY CONTACTING SIDES

V. V. Lazarev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 53-63.

The paper gives data structures to represent the geometric model decomposition into quadrangular and hexahedral blocks, which are used to construct a block-structured grid. These structures widen choices of block contact options, because blocks may have partially contacting sides. This significantly reduces the total number of blocks in decomposing one and the same geometric model. The advantages of using blocks with partially contacting sides are demonstrated by the example of the grid for a test model of a radiator header with guard.
The decomposition may lead to such interconnection of blocks that makes it impossible to construct a grid with node matching For this case, an effective algorithm is suggested to identify whether it is possible to construct a matched block grid, or not.


Key words: a block-structured grid, blocks with partially contacting sides, decomposition of a geometric model into blocks with matching grid nodes.
THE ScientificView PARALLEL POSTPROCESSING SYSTEM: THE CALCULATION OF "ADDITIONAL" GRID QUANTITIES

A. L. Potekhin, V. V. Zhirnov
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 64-72.

The paper describes algorithms of calculating additional grid quantities in the ScientificView parallel postprocessing system. The system has been being developed for the analysis and postprocessing of the physical process simulation data, including results of the solution of engineering problems using the “Logos” software package. Additional grid quantities can be calculated using different formulas and rules directly in the ScientificView system with the original quantity values obtained in the simulation.
The paper presents 14 groups of additional quantities depending on the way of calculating them, the computation module architecture, as well as the encountered problems and methods to resolve them. The user interface and data postprocessing results are presented.


Key words: the "Logos" software package, the ScientificView parallel postprocessing system, calculation of grid quantities, interpolation, calculator of quantities.
NEW CAPABILITIES OF A PARALLEL PROGRAM DEBUGGER (PD)

A. B. Kiselev, S. N. Kiselev
VANT. Ser.: Mat. Mod. Fiz. Proc. 2020. No 3. P. 73-80.

The paper describes new capabilities of a parallel program debugger (PD), such as non-interactive debugging, support of graphics accelerators and a "tree"- like communication scheme. Modifications to the graphical user´s interface are described.


Key words: a multiprocessor computer system, debugging of a parallel program, a parallel debugger.
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