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| Author | : Nikolas A. Kanarēs |
| Publisher | : |
| Total Pages | : 176 |
| Release | : 2012 |
| Genre | : Cylinders |
| ISBN | : |
| Author | : Salah Neffaa |
| Publisher | : |
| Total Pages | : 139 |
| Release | : 2010 |
| Genre | : |
| ISBN | : |
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.
| Author | : Matthieu Leroy |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2013 |
| Genre | : |
| ISBN | : |
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.
| Author | : Yuri Feldman |
| Publisher | : |
| Total Pages | : 127 |
| Release | : 2011 |
| Genre | : Fluid dynamics |
| ISBN | : |
| Author | : Maurice Meneguzzi |
| Publisher | : Springer |
| Total Pages | : 421 |
| Release | : 2014-03-12 |
| Genre | : Science |
| ISBN | : 9783662140239 |
Small-scale structures in turbulent flows appear as a subtle mixture of order and chaos that could play an important role in the energetics. The aim here is a better understanding of the similarities and differences between vortex and current dynamics, and of the influence of these structures on the statistical and transport properties of hydrodynamic and magnetohydrodynamic turbulence, with special concern for fusion plasmas, and solar or magnetospheric environments. Special emphasis is given to the intermittency at inertial scales and to the coherent structures at small scales. Magnetic reconnection and the dynamo effect are also discussed, together with the effect of stratification and inhomogeneity. The impact of hydrodynamic concepts on astro and geophysical observations are reviewed.
| Author | : Vítor Araújo |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 369 |
| Release | : 2010-06-10 |
| Genre | : Mathematics |
| ISBN | : 3642114148 |
In this book, the authors present the elements of a general theory for flows on three-dimensional compact boundaryless manifolds, encompassing flows with equilibria accumulated by regular orbits. The book aims to provide a global perspective of this theory and make it easier for the reader to digest the growing literature on this subject. This is not the first book on the subject of dynamical systems, but there are distinct aspects which together make this book unique. Firstly, this book treats mostly continuous time dynamical systems, instead of its discrete counterpart, exhaustively treated in some other texts. Secondly, this book treats all the subjects from a mathematical perspective with proofs of most of the results included. Thirdly, this book is meant to be an advanced graduate textbook and not just a reference book or monograph on the subject. This aspect is reflected in the way the cover material is presented, with careful and complete proofs, and precise references to topics in the book.
| Author | : Gary N. Coleman |
| Publisher | : |
| Total Pages | : |
| Release | : 1996 |
| Genre | : |
| ISBN | : |
| Author | : Oleg Mikhailovich Belotserkovskii |
| Publisher | : World Scientific |
| Total Pages | : 489 |
| Release | : 2009 |
| Genre | : Science |
| ISBN | : 9812833021 |
The book provides an original approach in the research of structural analysis of free developed shear compressible turbulence at high Reynolds number on the base of direct numerical simulation (DNS) and instability evolution for ideal medium (integral conservation laws) with approximate mechanism of dissipation (FLUX dissipative monotone OC upwindOCO difference schemes) and does not use any explicit sub-grid approximation and semi-empirical models of turbulence. Convective mixing is considered as a principal part of conservation law.
| Author | : Michel Deville |
| Publisher | : Vieweg+Teubner Verlag |
| Total Pages | : 394 |
| Release | : 2012-04-20 |
| Genre | : Technology & Engineering |
| ISBN | : 9783322898401 |
Der Sammelband enthält Beiträge einer Tagung über die Simulation von dreidimensionalen Flüssigkeiten. Sie geben einen Überblick über den Stand des Wissens auf dem Gebiet der numerischen Simulation der Turbulenz, angewandt auf eine weite Spanne von Problemen wie Aerodynamik, Nicht-Newtonsche Flüssigkeiten, Konvektion.This volume contains the material presented at the IMACS-COST Conference on CFD, Three-Dimensional Complex Flows, held in Lausanne (Switzerland), September 13 - 15, 1995. It gives an overview of the current state of numerical simulation and turbulence modelling applied to a wide range of fluid flow problems such as an example aerodynamics, non-Newtonian flows, transition, thermal convection.
| Author | : Jie Zhang |
| Publisher | : |
| Total Pages | : 145 |
| Release | : 2019 |
| Genre | : Computational fluid dynamics |
| ISBN | : 9789811063411 |
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.
