Download or read book Numerical simulations of compressible magnetohydrodynamic flows in a spherical geometry anglais written by Lorenzo Valdettaro and published by . This book was released on 1992 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dans cette thèse nous proposons une méthode de résolution numérique des équations MHD compressibles en géométrie sphérique basée sur une méthode pseudo-spectrale. Nous développons un schéma de résolution temporelle semi-implicite pour les termes diffusifs et les termes d'onde, qui permet de nous affranchir des contraintes sur le pas en temps d'une méthode purement explicite. La mise en œuvre numérique s'avère être aisée, et efficace lorsque le nombre de mach est proche de 1. Nous étudions ensuite l'erreur d'arrondi commise lors de la transformée de Fourier rapide, qui constitue l'une des briques de base du code numérique, et nous dégageons une nouvelle limitation théorique sur l'erreur d'arrondi commise par cet algorithme. Nous nous tournons ensuite vers les applications physiques. Nous étudions en premier lieu la convection compressible à l'intérieur d'une coquille sphérique à nombre de Rayleigh modéré (jusqu'à 20 fois le nombre de Rayleigh critique). Nous classifions les différents modes de convection stationnaire, périodique et bi-périodique. Nous abordons ensuite l'effet dynamo en effectuant une simulation numérique à grande résolution (utilisant 1000000 de points). L'écoulement compressible turbulent est dominé par des vortex cycloniques qui s'étendent sur toute l'épaisseur de la couche sphérique. Une partie du champ magnétique est créé dans ces vortex et advecte par eux. Une seconde zone de production de champ magnétique est située à la base de la zone convective, où l'on observe une forte rotation différentielle. Enfin, nous nous intéressons dans les écoulements MHD compressibles turbulents, et nous appliquons l'étude au cas des disques d'accrétion. Nous proposons pour ces objets un scénario de dissipation turbulente qui est en accord avec les observations.

Download or read book Numerical Simulation of Fluid Flow in Spherical Geometry and Two dimensional Magnetohydrodynamic Turbulence written by Cha-Mei Tang Hui and published by . This book was released on 1977 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Literature 1991 Part 2 written by Astronomisches Rechen-Institut and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 1592 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstrats are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.

Download or read book Three dimensional Direct Numerical Simulations of Hydrodynamic and Magnetohydrodynamic Flows Over an Obstacle in a Confined Geometry written by Nikolas A. Kanarēs and published by . This book was released on 2012 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence in Magnetohydrodynamics written by Andrey Beresnyak and published by Walter de Gruyter GmbH & Co KG. This book was released on 2019-07-08 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetohydrodynamics describes dynamics in electrically conductive fluids. These occur in our environment as well as in our atmosphere and magnetosphere, and play a role in the sun's interaction with our planet. In most cases these phenomena involve turbulences, and thus are very challenging to understand and calculate. A sound knowledge is needed to tackle these problems. This work gives the basic information on turbulence in nature, comtaining the needed equations, notions and numerical simulations. The current state of our knowledge and future implications of MHD turbulence are outlined systematically. It is indispensable for all scientists engaged in research of our atmosphere and in space science.

Download or read book Multi Wavelength Investigations of Solar Activity IAU S223 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2004 with total page 766 pages. Available in PDF, EPUB and Kindle. Book excerpt: These Proceedings present the most recent results from the highly successful international solar space missions (SOHO, CORONAS-F, TRACE, RHESSI, YOHKOH) and ground observatories around the Earth, reported at the IAU Symposium 223 held in St. Petersburg, Russia, June 14-19, 2004. These include discussions of the current theories of solar dynamics and activity, new constraints provided by the multi-wavelength observations of the Sun from the interior to the heliosphere, as well as discussions of future coordinated plans and efforts of multi-wavelength investigations of the Sun. The Proceedings contain the material of seven plenary sessions and three round-table discussions

Download or read book PASCAL written by and published by . This book was released on 1993 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Developments and the Applications of the Numerical Algorithms in Simulating the Incompressible Magnetohydrodynamics with Complex Boundaries and Free Surfaces written by Jie Zhang and published by . This book was released on 2019 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an accurate and advanced numerical methodology to remedy difficulties such as direct numerical simulation of magnetohydrodynamic (MHD) flow in computational fluid dynamics (CFD), grid generation processes in tokamak fusion facilities, and the coupling between the surface tension force and Lorentz force in the metallurgical industry. In addition, on the basis of the numerical platform it establishes, it also investigates selected interesting topics, e.g. single bubble motion under the influence of either vertical or horizontal magnetic fields. Furthermore, it confirms the relation between the bubble's path instability and wake instability, and observes the anisotropic (isotropic) effect of the vertical (horizontal) magnetic field on the vortex structures, which determines the dynamic behavior of the rising bubble. The direct numerical simulation of magnetohydrodynamic (MHD) flows has proven difficult in the field of computational fluid dynamic (CFD) research, because it not only concerns the coupling of the equations governing the electromagnetic field and the fluid motion, but also calls for suitable numerical methods for computing the electromagnetic field. In tokamak fusion facilities, where the MHD effect is significant and the flow domain is complex, the process of grid generation requires considerable time and effort. Moreover, in the metallurgical industry, where multiphase MHD flows are usually encountered, the coupling between the surface tension force and Lorentz force adds to the difficulty of deriving direct numerical simulations.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Magnetohydrodynamic Turbulence in Confined Domains written by Salah Neffaa and published by . This book was released on 2010 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we developed a Fourier pseudo-spectral code coupled with the volume penalization for the simulation of turbulent MHD flows with non-periodic boundary conditions. This method was validated with classical and academic test-cases. Then we studied the influence of the confinement with walls in a 2D configuration for decaying MHD and we found four decaying regimes which depend on the initial conditions. We also discussed the phenomenon of spontaneous rotation, or spin-up, in 2D non-axisymmetric geometries, originally discovered in hydrodynamic flows. We showed the influence of the Reynolds number and the magnetic pressure on this phenomenon. Finally, simulations of MHD flows in wall bounded three-dimensional domains were addressed. The first results concerning the simulation of decaying MHD turbulence in a cylinder imposing Dirichlet boundary conditions for both the velocity and the magnetic field showed the validity of the code and suggest good prospects for developing more physically justified boundary conditions for the magnetic field.

Download or read book Simulation of Three dimensional Magnetohydrodynamic Flows Using a Pseudo spectral Method with Volume Penalization written by Matthieu Leroy and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A volume penalization method for the simulation of magnetohydrodynamic (MHD) flows in confined domains is presented. Incompressible resistive MHD equations are solved in 3D by means of a parallelized pseudo-spectral solver. The volume penalization technique is an immersed boundary method, characterized by a high flexibility in the choice of the geometry of the considered flow. In the present case, it allows the use of conditions different from periodic boundaries in a Fourier pseudo-spectral scheme. The numerical method is validated and its convergence is assessed for two- and three-dimensional hydrodynamical and MHD flows by comparing the numerical results with those of the literature or analytical solutions. Then, the spontaneous generation of kinetic and magnetic angular momentum is studied for confined 2D and 3D MHD flows. The influence of the Reynolds number and of the ratio of kinetic/magnetic energies is explored, as well as the differences induced by the boundary conditions. The fact that axisymmetric borders introduce a non-zero pressure term in the evolution equation of the angular momentum is essential to generate large values of the angular momentum. It is investigated whether this self-organization is exclusively observed in 2D flows by considering 3D MHD in the presence of a strong axial magnetic field. The last part is devoted to the simulation of a conducting fluid in a periodic cylinder with imposed axial and poloidal magnetic forcing, implying a resulting magnetic field. By varying the amplitude of the poloidal forcing, different dynamical states can be achieved. The effect of the Prandtl number on the threshold of the instabilities is then studied.

Download or read book Numberical Simulation of Magnetohydrodynamic MHD Effect on Forced Natural and Mixed Convection Flows written by Dipin Kalapurakal and published by . This book was released on 2012 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The accurate simulation of magnetohydrodynamic (MHD) flows and heat transfer is critical to the understanding of the complex physics in liquid metal flows for coolant and breeder blankets used in fusion power plants such as tokamaks, metallurgy, aerospace applications and crystal growth. These issues will be addressed through an effort investigating low-magnetic Reynolds number (Rem), high-Hartmann number (Ha), MHD flows in a square cavity, using a 2D parallel vorticity-streamfunction-based incompressible Navier-Stokes code. Numerical simulations of MHD flow and heat transfer are carried out in a square cavity with emphasis on specific classical benchmark problems like the lid-driven cavity with and without heat transfer (forced convection), natural convection and mixed convection (forced + natural). Effects of Ha and Pr are investigated to assess MHD in heat transfer under various conditions. Quantities analyzed include streamfunction, vorticity, velocities, temperature and Nusselt number. Computations are carried out on in-house supercomputing desktops and clusters. This study provides a fundamental understanding of MHD effects on flow behavior and heat transfer in the context of a series of simple benchmark problems. Also created through this effort is an accurate and effcient incompressible code capable of calculating a variety of added complex physics in fluid mechanics.

Download or read book Numerical Simulations of Magnetohydrodynamic Flow and Heat Transfer written by Amar KC and published by . This book was released on 2014 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetohydrodynamic (MHD) natural convection in a porous medium with low-magnetic Reynolds number (Re[subscript m]) is investigated in a rectangular cavity with isothermal walls on the left and right and adiabatic walls on the top and bottom. The validity of Darcy's law is addressed for high-Rayleigh number (Ra) flows with high permeability, where the velocity-pressure gradient relationship transitions from linear (i.e. the Darcy law) to nonlinear, due to the fact that the form drag due to solid obstacles is now comparable with the surface drag due to friction, which in turn results in the Darcy-Forchheimer law. In addition, the effect of different magnetic field strengths in terms of Hartmann numbers (Ha) is also investigated for cavities for varying aspect ratios to analyze how the flow and thermal characteristics in a porous medium are influenced by the applied magnetic field. Here, the interaction between the fluid velocity and the electromagnetic forces gives rise to different flow scenarios. In particular, the influence of magnetic field under the varying conditions of convective currents (through Ra) and length scales (through aspect ratios) on quantities such as stream function, temperature and Nusselt number, Nu is studied. Assessment of three regularization-based models and two eddy-viscosity-based subgrid-scale (SGS) turbulence models for large eddy simulations (LES) are carried out for MHD decaying homogeneous turbulence (DHT) and MHD transition to turbulence for the Taylor-Green vortex (TGV) through comparisons to direct numerical simulations (DNS). Simulations are conducted using the low-magnetic Reynolds number approximation (Re[subscript m] “ 1) and the initially-isotropic turbulence problem has a Taylor scale Reynolds number (Re[subscript lambda]) of 120. LES predictions using the Leray-[alpha], LANS-[alpha], and Clark-[alpha] regularization-based SGS models are compared to the classic non-dynamic Smagorinsky and the dynamic Smagorinsky models. Regarding the regularization models, this work represents their first application to MHD decaying turbulence or transition-to-turbulence problems. Analyses of turbulent kinetic energy decay rates, energy spectra, and vorticity fields are made between the varying magnetic field cases. Overall, the regularization models did poorly compared to the eddy-viscosity models for all MHD cases, but the comparisons improved as the magnetic field increase in magnitude.

Download or read book Numerical Simulation of Compressible Viscous Magneto Hydrodynamics Equations with Chemical Kinetics written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the objectives of this research project have been achieved. In this first phase of the AFOSR grant (1 October 1998 - 30 September 2002), the principal investigator and his students have developed a 2-D unsteady compressible viscous magnetohydrodynamic code designated MHD2D which has been validated for 2-D internal and external flow & The code solves the coupled MHD equations (mass. momentum and energy equations of fluid flow including MHD effects (Lorentz force and Joule heating), magnetic induction equations and Maxwell equations) and includes an equilibrium air model for re gas effects, a finite-rate chemical kinetics model for dissociated air, several electrical conductivity models and a bi-temperature model. I-his code has been employed to investigate the concept of supersonic drag and heat transfer reduction by modification/dissipation of shock waves in the presence of strong magnetic fields. A series of numerical experiments for blunt body flows and scramjet inlet flow fields have been conducted by varying the Mach number, Reynolds number, degree of ionization of the air plasma and the intensity of the magnetic field to understand the physics of the phenomena and its potential for supersonic drag reduction in practical applications.

Download or read book Numerical Simulations of Incompressible Flows in Complex Geometries written by Konstantinos Vogiatzis and published by . This book was released on 2001 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence and Nonlinear Dynamics in MHD Flows written by M. Meneguzzi and published by Elsevier. This book was released on 2012-12-02 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topics discussed at this international workshop include: magnetic fields in astrophysical flows, slow and fast dynamos, MHD turbulence in space plasmas and in the laboratory, exact solutions to MHD, topology and chaos in MHD, helicity and velocity-magnetic correlations, turbulent reconnection and non-magnetic flows.