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Two-dimensional finite-difference lattice Boltzmann method for the complete Navier-Stokes equations of binary fluids

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EUROPHYSICS LETTERS 2005年第2期69卷 214-220页

作者： Xu, AG Kyoto Univ Dept Phys Sakyo Ku Kyoto 6068501 Japan

Based on Sirovich's two-fluid kinetic theory and on a dodecagonal discrete-velocity model, a two-dimensional 61-velocity finite-difference lattice Boltzmann method for the complete Navier-Stokes equations of binary fluids is formulated. Previous constraints, in most existing lattice Boltzmann methods, on the studied systems, like isothermal and nearly incompressible, are released within the present method. This method is designed to simulate compressible and thermal binary-fluid mixtures. The validity of the proposed method is verified by investigating i) the Couette flow and ii) the uniform relaxation process of the two components.

关键词： computational methods in fluid dynamics Kinetic and transport theory of gases Kinetic theory

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Simulating astrophysical phenomena:: challenges and achievements

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COMPUTER PHYSICS COMMUNICATIONS 2005年第1-3期169卷 353-361页

作者： Müller, E Max Planck Inst Astrophys D-85748 Garching Germany

Simulation is an indispensable and expedient tool for understanding many astrophysical phenomena. Addressing a few challenging computational problems in astrophysics, it is illustrated that simulation can provide the link between observations and theoretical models of astrophysical phenomenon. For obvious reasons, the discussion is restricted to a few specific timely problems, the main bias being the personal involvement of the author into the simulation of these astrophysics problems. In particular, recent work on core collapse supenovae and their gravitational wave signal, on extragalactic jets, and on the modeling of gamma-ray burst sources is presented. (c) 2005 Elsevier B.V. All rights reserved.

关键词： gravitational waves computational methods in fluid dynamics supernovae jets and bursts gamma-ray bursts

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MHD simulations and astrophysical applications

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FUNDAMENTALS OF SPACE ENVIRONMENT SCIENCE 2005年第5期35卷 899-907页

作者： Gómez, DO Mininni, PD Dmitruk, P Univ Buenos Aires Fac Ciencias Exactas & Nat Dept Fis RA-1428 Buenos Aires DF Argentina Inst Astron & Fis Espacio RA-1428 Buenos Aires DF Argentina Univ Delaware Bartol Res Inst Newark DE 19716 USA

Magnetohydrodynamics is an adequate theoretical framework to study a large variety of astrophysical flows. The generation of magnetic fields by dynamo mechanisms, the development of turbulent flows or the topological change of magnetic fields by reconnection, are just a few examples. First, we describe the basic features of the MHD framework. Second, we make a brief introduction to the physical processes listed above, namely: dynamo action, MHD turbulence, and magnetic reconnection. Finally, we show the results arising from numerical simulations of these processes, for a number of configurations of astrophysical interest. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

关键词： computational methods in fluid dynamics turbulence simulation and modeling astrophysical flows magnetic reconnections astrophysics

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Simulating astrophysical phenomena:: challenges and achievements

Simulating astrophysical phenomena:: challenges and achievem...

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Europhysics Conference on computational Physics

作者： Müller, E Max Planck Inst Astrophys D-85748 Garching Germany

关键词： gravitational waves computational methods in fluid dynamics supernovae jets and bursts gamma-ray bursts

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MHD simulations and astrophysical applications

MHD simulations and astrophysical applications

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1st Latin-American Advanced School on Space Environment

关键词： computational methods in fluid dynamics turbulence simulation and modeling astrophysical flows magnetic reconnections astrophysics

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A lattice Boltzmann model with random dynamical constraints

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EUROPEAN PHYSICAL JOURNAL B 2004年第2期39卷 241-247页

作者： Lamura, A Succi, S CNR Ist Applicaz Calcolo Sez Bari I-70126 Bari Italy CNR Ist Applicaz Calcolo I-00161 Rome Italy

In this paper we introduce a modified lattice Boltzmann model (LBM) with the capability of mimicking a fluid system with dynamic heterogeneities. The physical system is modeled as a one-dimensional fluid, interacting with finite-lifetime moving obstacles. fluid motion is described by a lattice Boltzmann equation and obstacles are randomly distributed semi-permeable barriers which constrain the motion of the fluid particles. After a lifetime delay, obstacles move to new random positions. It is found that the non-linearly coupled dynamics of the fluid and obstacles produces heterogeneous patterns in fluid density and non-exponential relaxation of two-time autocorrelation function.

关键词： computational methods in fluid dynamics Nonequilibrium and irreversible thermodynamics

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(2+1) dimensional Haragus-Courcelle-Il'ichev model for the liquid surface waves in the presence of sea ice or surface tension: Backlund transformation, exact solutions and possibly observable effects

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EUROPEAN PHYSICAL JOURNAL B 2004年第3期42卷 441-450页

作者： Tian, B Gao, YT Beijing Univ Posts & Telecommun Sch Sci Beijing 100876 Peoples R China Beijing Univ Aeronaut & Astronaut State Key Lab Software Dev Environm Beijing 100083 Peoples R China CCAST World Lab Beijing 100080 Peoples R China Beijing Univ Aeronaut & Astronaut Minist Ed Key Lab Fluid Mech Beijing 100083 Peoples R China Beijing Univ Aeronaut & Astronaut Natl Lab Computat Fluid Dynam Beijing 100083 Peoples R China

The wave propagation on an ocean or water surface in the presence of sea ice or surface tension is of current importance. In this paper, we investigate the (2+1) dimensional 6th-order model proposed recently by Haragus-Courcelle and Il'ichev for such wave propagation. Firstly, we correct some errors in the original derivations of this model. With computerized symbolic computation and truncated Painleve expansion. we then obtain an auto-Backlund transformation and types of the solitonic and other exact analytic solutions to the model, with the solitary waves as a special case, able to be dealt with the powerful Wu method. Based on the results, we later propose some possibly observable effects for the future experiments. and in the end, provide a possible way to explain the regular structure of the open-sea ice break-up observations.

关键词： computational methods in fluid dynamics Solitons Hydrodynamic waves Symbolic computation (computer algebra)

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Understanding turbulence through numerical simulations

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2004年第1-2期342卷 69-75页

作者： Gómez, DO Mininni, PD Univ Buenos Aires Fac Ciencias Exactas & Nat Dept Fis RA-1428 Buenos Aires DF Argentina Univ Buenos Aires CONICET IAFE RA-1428 Buenos Aires DF Argentina

Turbulence is one of the important problems in classical physics that still remain unsolved. The Navier-Stokes equations have been studied for almost two centuries now, and although they seem to properly describe the dynamics of fluids, we still do not have a clear understanding of even the simplest turbulent flows. We present numerical simulations of three dimensional, homogeneous and isotropic turbulence at moderate Reynolds numbers. We externally drive the fluid with either helical or non-helical forces. In both cases we find that the externally driven system relaxes to a stationary turbulent regime, which is compatible with the Kolmogorov spectrum E-k approximate to k(-5/3). In the helical case, we confirm that the kinetic helicity also cascades directly, along with energy and displaying a Kolmogorov spectrum as well. We find that the dissipation scale of both ideal invariants is also consistent with the Kolmogorov scale (i.e., k(v) approximate to (epsilon/nu(3))(1/4)). (C) 2004 Published by Elsevier B.V.

关键词： computational methods in fluid dynamics turbulence simulation and modeling

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Understanding turbulence through numerical simulations

Understanding turbulence through numerical simulations

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8th Latin American Workshop[ on Nonlinear Phenomena

作者： Gómez, DO Mininni, PD Univ Buenos Aires Fac Ciencias Exactas & Nat Dept Fis RA-1428 Buenos Aires DF Argentina Univ Buenos Aires CONICET IAFE RA-1428 Buenos Aires DF Argentina

关键词： computational methods in fluid dynamics turbulence simulation and modeling

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Mathematical simulation of one-dimensional dam-collapse flow over wetted bed

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EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS 2003年第2期22卷 133-142页

作者： Medkour, D Kadja, M Ben Mhidi Univ Inst Mech Oum El Bouaghi 04000 Algeria Mentouri Univ Dept Mech Constantine 25000 Algeria

A mathematical model is described and applied to simulate sudden total one-dimensional dam-break flow over wetted bed. The dam collapse takes place in a rough sloping non-prismatic channel of various cross-sections. The water parameters to be instantaneously calculated are the height h, the discharge Q, the mean velocity u and the pressure force P. The mentioned. flow is governed by the Saint-Venant shallow water equations and the computation process, on the basis of rectangular grid of points, consists of two complementary solutions: (a) at the first instant after the collapse, an analytical procedure is considered. The calculated parameters are taken as initial values in the water stream embraced by the flood wave. Outside this zone, initial conditions are those which preexist before the rupture. (b) Beyond this time, a numerical computation is carried out by using an iterative explicit method of characteristics. ( c) Every time stage of calculation starts by determining the discontinuity ( wave front) parameters namely its abscissa x(delta), height h(delta), celerity c(delta) and alert delay t(delta). The former is the discontinuity arrival time at considered station. Typical results are obtained and compared with similar ones already published by others in the literature.

关键词： Numerical simulation, solution of equations Hydrodynamic waves computational methods in fluid dynamics

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