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Author: Victoria R. Winters Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Understanding the underlying dynamics of turbulence in magnetic confinement fusion experiments is extremely important. Turbulence greatly reduces the confinement time of these devices and therefore greater knowledge of turbulent dynamics can help with its mitigation. Experiments from the Alcator C-Mod tokamak [18] provide support for a theory that edge turbulence in tokamak fusion plasmas is the result of deterministic chaos, rather than stochastic processes [15]. Using readily available reflectometer data from Alcator C-Mod (C-Mod), analysis of C-Mod edge turbulence in Ohmic plasmas and Ion Cyclotron Range of Frequencies (ICRF) heated L-Mode plasmas shows that density fluctuations just inside or at the Last Closed Flux Surface (LCFS) exhibit exponential power spectra. Theoretically, the characteristic slope of the data on a semi-log plot gives the full width of the underlying Lorentzian pulses, which give rise to the exponential power spectra due to the dynamics of deterministic chaos. Using a separate fitting routine, individual Lorentzian pulses in the reflectometer time series data are identified, and the widths of the Lorentzian pulses match the inverse characteristic frequency of the exponential power spectra. Analysis of the waiting times between pulses and the pulse amplitudes indicate these are randomly distributed yet the pulse widths have a narrow distribution. These characteristics are consistent with a chaotic process. There is also a preliminary comparison of GPI data and a discussion of limitations of the analysis presented here and plans for future work. Overall, the experimental results in this study are consistent with edge turbulence that is at least partially generated by chaotic dynamics.
Author: Victoria R. Winters Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Understanding the underlying dynamics of turbulence in magnetic confinement fusion experiments is extremely important. Turbulence greatly reduces the confinement time of these devices and therefore greater knowledge of turbulent dynamics can help with its mitigation. Experiments from the Alcator C-Mod tokamak [18] provide support for a theory that edge turbulence in tokamak fusion plasmas is the result of deterministic chaos, rather than stochastic processes [15]. Using readily available reflectometer data from Alcator C-Mod (C-Mod), analysis of C-Mod edge turbulence in Ohmic plasmas and Ion Cyclotron Range of Frequencies (ICRF) heated L-Mode plasmas shows that density fluctuations just inside or at the Last Closed Flux Surface (LCFS) exhibit exponential power spectra. Theoretically, the characteristic slope of the data on a semi-log plot gives the full width of the underlying Lorentzian pulses, which give rise to the exponential power spectra due to the dynamics of deterministic chaos. Using a separate fitting routine, individual Lorentzian pulses in the reflectometer time series data are identified, and the widths of the Lorentzian pulses match the inverse characteristic frequency of the exponential power spectra. Analysis of the waiting times between pulses and the pulse amplitudes indicate these are randomly distributed yet the pulse widths have a narrow distribution. These characteristics are consistent with a chaotic process. There is also a preliminary comparison of GPI data and a discussion of limitations of the analysis presented here and plans for future work. Overall, the experimental results in this study are consistent with edge turbulence that is at least partially generated by chaotic dynamics.
Author: James L. Terry Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
The intermittent turbulent transport in the scrape-off-layers of Alcator C-Mod, DIII-D, and NSTX is studied experimentally. On DIII-D the fluctuations of both density and temperature have strongly non-Gaussian statistics, and events with amplitudes above 10 times the mean level are responsible for large fractions of the net particle and heat transport, indicating the importance of turbulence on the transport. In C-Mod and NSTX the turbulence is imaged with a very high density of spatial measurements. The 2-D structure and dynamics of emission from a localized gas puff are observed, and intermittent features (also sometimes called 3blobs4) are typically seen. On DIII-D the turbulence is imaged using BES and similar intermittent features are seen. The dynamics of these intermittent features are discussed. The experimental observations are compared with numerical simulations of edge turbulence. The electromagnetic turbulence in a 3-D geometry is computed using non-linear plasma fluid equations. The wavenumber spectra in the poloidal dimension of the simulations are in reasonable agreement with those of the C-Mod experimental images once the response of the optical system is accounted for. The resistive ballooning mode is the dominant linear instability in the simulations.
Author: Alexandre Favre Publisher: ISBN: Category : Psychology Languages : en Pages : 216
Book Description
"I found this most unusual book to be very stimulating. It really did achieve its objective of breaking academic barriers and showing how researchers in different disciplines are grappling with the same difficulties in using different conceptual and practicalmethodologies, and in explaining their results... I found many aspects of my own thinking about fluid mechanics and the philosophy of science changing as I read the book and discussed it with colleagues and friends."--Julian C. R. Hunt, reviewing the French edition.
Author: Heinz Georg Schuster Publisher: John Wiley & Sons ISBN: 3527606416 Category : Science Languages : en Pages : 312
Book Description
A new edition of this well-established monograph, this volume provides a comprehensive overview over the still fascinating field of chaos research. The authors include recent developments such as systems with restricted degrees of freedom but put also a strong emphasis on the mathematical foundations. Partly illustrated in color, this fourth edition features new sections from applied nonlinear science, like control of chaos, synchronisation of nonlinear systems, and turbulence, as well as recent theoretical concepts like strange nonchaotic attractors, on-off intermittency and spatio-temporal chaotic motion.
Author: Pierre Berge Publisher: Wiley-VCH ISBN: Category : Science Languages : en Pages : 358
Book Description
Presented at a relatively elementary level, this introduction to the study of dissipative dynamical systems is addressed to an audience which is scientifically cultivated but not specialized in this discipline. Encompasses the analysis of all time-dependent phenomena, treating the major types of behavior or of evolution without direct reference to the material aspects. Focuses on physics and chemistry and avoids mathematical treatment. In a panorama which is coherent and accessible, it describes concretely the important dynamical phenomena and the way in which they appear in experimental reality. Covers basic vocabulary and regular periodic behavior, and goes on to apply them in analytical methods.
Author: David Ruelle Publisher: World Scientific Publishing Company Incorporated ISBN: 9789810223113 Category : Science Languages : en Pages : 469
Book Description
The present collection of reprints covers the main contributions of David Ruelle, and coauthors, to the theory of chaos and its applications. Several of the papers reproduced here are classics in the field. Others (that were published in less accessible places) may still surprise the reader.The collection contains mathematical articles relevant to chaos, specific articles on the theory, and articles on applications to hydrodynamical turbulence, chemical oscillations, etc.A sound judgement of the value of techniques and applications is crucial in the interdisciplinary field of chaos. For a critical assessment of what has been achieved in this area, the present volume is an invaluable contribution.
Author: Victoria R. Winters
Author: Victoria R. Winters
Author: James L. Terry
Author: Alexandre Favre
Author: Heinz Georg Schuster
Author: Pierre Berge
Author: M. H. Redi
Author: Fabio Benatti
Author: David Hobill
Author: Ricardo Lima
Author: David Ruelle