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Scale effects in internal wave attractors

Physical Review Fluids 2017年第11期2卷 114803-114803页

作者： C. Brouzet I. N. Sibgatullin E. V. Ermanyuk S. Joubaud T. Dauxois Université de Lyon ENS de Lyon Université Claude Bernard CNRS Laboratoire de Physique F-69342 Lyon France Moscow State University 119991 Moscow Russia Institute for System Programming 109004 Moscow Russia Shirshov Institute of Oceanology 117997 Moscow Russia Lavrentyev Institute of Hydrodynamics Novosibirsk 630090 Russia Novosibirsk State University Novosibirsk 630090 Russia

As a necessary preliminary step toward geophysically significant extrapolations, we study the scale effects in internal wave attractors in the linear and nonlinear regimes. We use two geometrically similar experimental setups, scaled to factor 3, and numerical simulations (a spectral element method, based on the Nek5000 open solver) for a range of parameters that is typically accessible in laboratory. In the linear regime, we recover the classical viscous scaling for the beam width, which is not affected by variations of the amplitude of the input perturbation. In the nonlinear regime, we show that the scaling of the width-to-length ratio of the attractor branches is intimately related with the energy cascade from large-scale energy input to dissipation. We present results for the wavelength, amplitude, and width of the beam as a function of time and as a function of the amplitude of the forcing.

关键词： Flow instability Geophysical fluid dynamics Stratified geophysical flows Hydrodynamic waves

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Improved algorithm of boundary integral equation approximation in 2D vortex method for flow simulation around curvilinear airfoil

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AIP Conference Proceedings 2018年第1期2027卷

作者： Ilia Marchevsky Kseniia Kuzmina Irina Soldatova Bauman Moscow State Technical University 2-nd Baumanskaya st. 5 105005 Moscow Russia Ivannikov Institute for System Programming of the Russian Academy of Sciences Alexander Solzhenitsyn st. 25 109004 Moscow Russia

The problem of the accuracy improving is considered for vortex method. It is shown, that the airfoil surface line representation as a polygon consisting of rectilinear panels can lead to incorrect behavior of the numerical solution of boundary integral equation with respect to unknown vortex sheet intensity, especially in case of considerably different lengths of the neighboring panels. The approach is developed which makes it possible to take into account explicitly the curvature of the surface line. The approximate formulae for the coefficients of linear system are derived which permit to obtain rather “good” numerical solution for arbitrary airfoil discretization.

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Assessment of Turbulent Wake Behind two Wind Turbines Using Multi-Fractal Analysis

Assessment of Turbulent Wake Behind two Wind Turbines Using ...

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Ivannikov ISPRAS Open Conference (ISPRAS)

作者： Arina Kryuchkova Jackson Tellez-Alvarez Sergei Strijhak Jose M. Redondo Russian Academy of Sciences Ivannikov Institute for System Programming of the Russian Academy of Sciences Moscow Russia Department of Civil and Environmental Engineering Technical University of Catalonia BarcelonaTech Barcelona Spain Department of Physics Technical University of Catalonia BarcelonaTech Barcleona Spain

In this paper we present preliminary results of the multi-fractal analysis for describing the behavior of turbulence evolution in the wake behind two model wind turbines using the program ImaCal. The wind energy is an important component of renewable energy sources. Nowadays the research community focuses on studying the turbulent wakes behind wind turbines and its interactions with the Atmospheric Boundary Layer. For finding the fractal dimension a multi-fractal analysis was performed using the results of a numerical simulation of the flow over two model wind turbines. The latter was carried out by means of the Large Eddy method with the Lagrangian Dynamic Smagorinsky subgrid model. The SOWFA library was employed as a part of OpenFoam software to perform the simulation.

关键词： Wind turbines Blades Mathematical model Computational modeling Atmospheric modeling Software Poles and towers

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Development of OpenFOAM Solver for Compressible Viscous Flows Simulation Using Quasi-Gas Dynamic Equations

Development of OpenFOAM Solver for Compressible Viscous Flow...

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Ivannikov ISPRAS Open Conference (ISPRAS)

作者： Matvey V. Kraposhin Daniil A. Ryazanov Elena V. Smirnova Tatiana G. Elizarova Maria A. Istomina Ivannikov Institute for System Programming of Russian Academy of Sciences Moscow Russia Dept. of wave and gas dynamics Lomonosov Moscow State University Moscow Russia Bauman Moscow State Technical University Moscow Russia Keldysh Institute of Applied Mathematics (Russian Academy of Sciences) Moscow Russia

Results of QGD (quasi-gas dynamics) equations approximation using OpenFOAM Finite Volume Method library are presented. The new developed solver QGDFoam compared to standard OpenFOAM solver rhoCentralFoam. Two approaches for the approximation of QGD terms are considered and compared - (1) least square method and (2) face normal derivative. Qualitative analysis showed that the first approach is more accurate compared with the second one and is preferable for reproducing complex shock interactions during unsteady flow. It was shown that the second approach produces the solution, similar to rhoCentralFoam solver with upwind interpolation. Being more diffusive than rhoCentralFoam solver with TVD schemes, QGDFoam, allows, however, to reproduce flows at wider Mach number range without introducing too much numerical diffusion comparing to upwind interpolation. Parallel scalability of developed solver has been checked. It scales for meshes down to approximately 1000 cells per node.

关键词： Mathematical model Face Numerical models Viscosity Interpolation Heating systems Shape

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An approach to instruction stream generation for functional verification of microprocessor designs

An approach to instruction stream generation for functional ...

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East-West Design & Test Symposium (EWDTS)

作者： Andrei Tatarnikov Institute for System Programming of the Russian Academy of Sciences Moscow Russia

ISBN: (纸本)9781509006946

The paper proposes an approach to instruction stream generation for verification of microprocessor designs. The approach is based on using formal specifications of the instruction set architecture as a source of knowledge about the design under verification. This knowledge is processed with generic engines implementing an extensible set of generation strategies to produce stimuli in the form of instruction sequences. Generation tasks are formulated using high-level descriptions that specify target instructions and strategies of sequence construction and data generation. This provides a flexible way to generate deterministic, random and constraint-based stimuli for verification of arbitrary architectures with minimum effort. The proposed approach has been successfully applied in industrial projects for verification of ARMv8 and MIPS64 microprocessor designs.

关键词： Registers Microprocessors Generators Software Engines Syntactics Computer architecture

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Distributed Generation of Mobile Call Graphs with DPLN Degree Distribution

Distributed Generation of Mobile Call Graphs with DPLN Degre...

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Ivannikov ISPRAS Open Conference (ISPRAS)

作者： Kyrylo Chykhradze Ivan Malyshev Denis Turdakov Anton Korshunov Ivannikov Institute for System Programming of the Russian Academy of Sciences Moscow Russia Ivannikov Inst. for Syst. Program. Moscow Russia National Research University Higher School of Economics Moscow Russia Lomonosov Moscow State University Moscow Russia

Networks of human interactions (like social and mobile call networks) in most cases inherit natural properties of society, e.g. community structure or tie strength. The method for generating large random mobile call graphs is introduced. Generated graphs reflect real network properties, such as community structure or Double Pareto Log-Normal degree distribution. Generation time is linear in the number of edges. The proposed method is intended to facilitate evaluation of algorithms designed for mobile call network analysis.

关键词： Mobile communication Generators Mobile computing Process control Data models Bipartite graph Benchmark testing

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Modular Fault Diagnosis in Fixed-Block Railway Signaling systems

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IFAC-PapersOnLine 2016年第3期49卷 459-464页

作者： Durmus, Mustafa S. Ustoglu, lker Tsarev, Roman Y. Schwarz, Michael Electrical and Electronics Engineering Department Pamukkale University Denizli Turkey Control and Automation Engineering Department Yildiz Technical University Istanbul Turkey Institute of Space and Information Technology Siberian Federal University Krasnoyarsk Russia Computer Architecture and System Programming Kassel University Kassel Germany

The diagnosis of possible faults in railway signaling systems is an important issue to provide safe travel and transportation in railways. Signaling system designers have to consider the possible faults which may occur in railway field components both on the requirements preparation phase and on the development phase of the signaling system software or namely, the interlocking system. Although the diagnosis of different unobservable faults is relatively hard, especially for large scale railway fields, this complexity can be overcome by using the Discrete Event system (DES) based modular diagnosis approach which is explained in this paper. The main advantage of using such modular approach for fault diagnosis in fixed-block signaling systems is the inspection of the diagnosability of the whole system with respect to its subsystems (railway field components). In this study, the diagnosability of the railway field equipment and the whole system is also explained with a case study. © 2016

关键词： Fault detection Discrete event simulation Failure analysis Railroad signal systems Railroads Signaling Development phase Field components Field equipment Fixed block signaling Interlocking systems Modular approach Railway signaling systems Signaling systems

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On investigation and efficient software implementation of fast methods for vortex influence computation in 2D flow simulation

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AIP Conference Proceedings 2018年第1期2027卷

作者： Evgeniya Ryatina Kseniia Kuzmina Ilia Marchevsky 1Bauman Moscow State Technical University 2-nd Baumanskaya st. 5 105005 Moscow Russia 2Ivannikov Institute for System Programming of the Russian Academy of Sciences Alexander Solzhenitsyn st. 25 109004 Moscow Russia

Two different fast methods are considered, which make it possible to compute approximately the velocity induced by given vorticity distribution. Such problem arises in incompressible flows simulation by using Lagrangian vortex methods. The usage of such fast methods permits to avoid the computation of mutual influence between all the pairs of vortex element and reduce the numerical complexity of the problem from O(n2) to O(n log n), where n is total number of vortex elements in the flow which model the vorticity distribution. The first of these methods is similar to the Barnes–Hut fast method, which initially had been developed for approximate solution of the n-body gravitational problem. The second one is based on the possibility of fast solution of the discrete analogue of the Poisson’s equation for the stream function by using Fast Fourier Transform (FFT). The estimations of numerical complexities for both methods are derived, which show some advantage of the second (FFT-based) approach at large numbers of vortex elements. This approach is also preferable with respect to the efficiency of software implementation.

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High-resolution simulation of internal waves attractors and impact of interaction of high amplitude internal waves with walls on dynamics of waves attractors 7

High-resolution simulation of internal waves attractors and ...

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7th European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS Congress 2016

作者： Sibgatullin, Ilias Kalugin, Michael Institute of System Programming Solzhenitsina str. 25 Moscow Russia Moscow State University Faculty of Mechanics and Mathematics Main Building GSP-1 1 Leninskiye Gory Moscow119991 Russia

ISBN: (纸本)9786188284401

Internal wave attractors have received great attention since its discovery in 1995 by Leo Maas ([1, 2]). Now convectional theory describing the formation of attractors is generally accepted, and the principal interest of researchers in recent years is focused on nonlinear interactions. A number of theories had been proposed and now nonlinear interaction due to triadic resonance is accepted as a principle cause of instability of attractors, in which case the parent wave of large amplitude gives birth to two daughter waves, such that conditions of triadic resonance are fulfilled for all the three waves [3]. All this presumes that wave-wall interaction participate in the process only by focusing-defocusing of energy on the inclined boundaries. Here we address interactions of large amplitude internal waves with the boundaries in real laboratory conditions, where Prandtl-Schmidt number is equal to 700. We show that large amplitude waves produce folded structures which are clearly visible on density-gradient images, as if produced by "kneading the dough". These structures are not quickly dissipated due to high Schmidt number and with time they propagate to the interior of the domain, as was shown by our numerical simulation. These structures have visible impact on the instability of attractor and the whole picture of turbulent motion for large amplitudes. The mechanism of interaction of these structures with internal gravity waves structures is the subject of further research. Numerical simulation is quite challenging due to high Prandtl-Schmidt number and small scale of the folded structures in highly nonlinear regimes. Also study is performed on large time scales. As a consequence most of conventional computational approaches give unreliable results. We have applied spectral element approach base on code nek5000 by Paul Fischer. It allowed us to carefully follow the fine space structures on large time scales.

关键词： Numerical models

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Numerical modelling of two-dimensional perfect gas flows using RKDG method on unstructured meshes

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AIP Conference Proceedings 2018年第1期2027卷

作者： V. N. Korchagova I. N. Fufaev V. V. Lukin S. M. Sautkina Applied mathematics dep. Bauman Moscow State Technical University 2-nd Baumanskaya st. 5 Moscow 105005 Russia Ivannikov Institute for System Programming of the RAS Alexander Solzhenitsyn st. 25 Moscow 109004 Russia Keldysh Institute of Applied Mathematics Miusskaya sq. 4 Moscow 125047 Russia

This paper is devoted to the simulation of the two-dimensional gas flows with oscillations and discontinuities using the Runge — Kutta Discontinuous Galerkin (RKDG) method, that has been implemented in the code prototype written in C++. It implements the HLLC numerical flux, the KXRCF troubled cells indicator, the WENO S limiter with the local characteristic decomposition approach and algorithm of dynamic time step control. The computations could be performed on unstructured meshes with mixed cell types (quadrangular and triangular) which can be built in any mesh bulder in IDEAS UNV format (i.e. SALOME). The code is verified on the common numerical tests such as pulsating and vibrating cylinders, Sod-like cylindrical explosion, forward-facing step, blast wave problem. Comparison between analytical solution and numerical results obtained with the in-house code and the open-source OpenFOAM package is presented.

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