Download or read book Role of Zonal Flow in Turbulent Transport Scaling written by Zhihong Lin and published by . This book was released on 2000 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Role of Zonal Flow in Turbulent Transport Scaling written by Zhihong Lin and published by . This book was released on 2000 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence and Diffusion written by Oleg G. Bakunin and published by Springer Science & Business Media. This book was released on 2008-08-15 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is intended to serve as an introduction to the multidisciplinary ?eld of anomalous diffusion in complex systems such as turbulent plasma, convective rolls, zonal ?ow systems, stochastic magnetic ?elds, etc. In spite of its great importance, turbulent transport has received comparatively little treatment in published mo- graphs. This book attempts a comprehensive description of the scaling approach to turbulent diffusion. From the methodological point of view, the book focuses on the general use of correlation estimates, quasilinear equations, and continuous time random walk - proach. I provide a detailed structure of some derivations when they may be useful for more general purposes. Correlation methods are ?exible tools to obtain tra- port scalings that give priority to the richness of ingredients in a physical pr- lem. The mathematical description developed here is not meant to provide a set of “recipes” for hydrodynamical turbulence or plasma turbulence; rather, it serves to develop the reader’s physical intuition and understanding of the correlation mec- nisms involved.
Download or read book Theoretical Studies of Interaction Between Drift Waves and Zonal Flows written by Zehua Guo and published by . This book was released on 2009 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: The size scaling of confinement properties in magnetized plasmas is one of the crucial and challenging problems of fusion energy research. It has been pointed out [64] that turbulence spreading is responsible for the local turbulence intensity dependence on the global equilibrium properties, i.e., the system size, and, ultimately, for the size scaling of turbulent transport coefficients. In the present work, first we investigate the slab analysis [46] for the spatio-temporal evolution of the drift wave(DW) radial envelope and zonal flow(ZF) amplitude. The derived two-field DW-ZF description reduces to the well-known coherent four-wave modulation interaction model [13] when separating the pump wave and its side bands. Stationary solution of the resulting coupled partial differential equations in a simple limit suggests formation of DW-ZF solitons, due to competition between DW dispersion and nonlinear ZF modulation. It is shown that the hyperbolic-secant DW soliton structure can propagate at group velocity which depends on the envelope peak amplitude. Additional interesting physics, i.e., birth and death, collision, reflection of solitons, can be produced by effects of linear growth/damping, dissipation and equilibrium nonuniformities. Turbulence bursting or intermittency can also be understood within soliton dynamics. The propagation of soliton causes significant radial spreading of initially localized DW turbulence and therefore can affect transport scaling by increasing the radial turbulent region. Further discussion about the correspondence to the two-field DW-ZF description in toroidal geometry [14] will also be presented.
Download or read book Zonal Flow Dynamics and Size scaling of Anomalous Transport written by Liu Chen and published by . This book was released on 2003 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Collisional Zonal Flow Damping on Turbulent Transport written by Zhihong Lin and published by . This book was released on 1999 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zonal Flow Generation in Toroidally Confined Plasmasthrough Modulational Instability of Drift Waves written by Raden Farzand Abdullatif and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of zonal flow constitutes an important part in the venture for achieving a controlled fusion reactor because of its role in mitigating turbulent transport. In this thesis, generation of zonal flow by modulational instability is discussed in a simple slab geometry, both in cold and hot ion models. In the case of cold ions with no resistivity, analysis on the Hasegawa-Mima equation results in a real Nonlinear Schroedinger equation, derived both heuristically and formally, through multiple length and time scale asymptotic expansions. In the collisional case, a non-linear Schroedinger equation with growth, otherwise known as the Ginzburg-Landau equation, is derived. In the simplest analysis it is shown that when a modulational instability criterion is ful- filled, zonal flow will be spontaneously generated from drift waves, with the growth rate of zonal flows increasing linearly with the zonal flow wave number. The growth rate cannot go up indefinitely but should peak at some zonal flow wave number, which is found using the non-linear Schroedinger equation. Nonlinearity is the key ingredient in the modulational instability generation of zonal flows. It is confirmed in this thesis that the potential perturbation of drift-wave has to be split into a fast fluctuating part and a slowly varying surface-averaged part, and thus the original Hasegawa-Mima equation is modified. Unless such modification is made, the nonlinear interaction in the original Hasegawa-Mima equation vanishes. In the formal derivation, analyses on the equation are carried out order by order. It is found that the nonlinear interplay appears at higher orders between the fast and slow component of the fluctuation. The Ginzburg-Landau equation is derived in this work from a set of potential and density fluctuation equations, known as the Hasegawa-Wakatani equations. These equations take account of resistivity and viscosity of the plasma, which are subsequently found to cause a phase shift between the potential and density amplitude. At a particular order in the asymptotic expansion analysis, it is found that resistivity and viscosity compete. When resistivity prevails, due to a phase shift between the potential and density amplitude, appearing from resistivity, the drift wave linearly grows. It is found that such drift-waves fall between a range of wavenumbers. In the hot ion case, the ion temperature gradient is taken into account. The equation describing the ion temperature gradient (ITG) is derived in this work by the multiple scale asymptotic expansion from the fundamental set of ion and electron equations of motion, ion continuity equation, and the heat-pressure balance equation. Assuming no collisions, in this model of ITG equation it is found that the ITG mode is unstable at a certain domain value of temperature gradient. The non-linear Schroedinger equation derived by further analysis of the ITG equation gives the condition for the modulational instability of the ITG mode. This condition is reduced to that of drift-waves when the temperature gradient is set to zero.
Download or read book Fusion Physics written by MITSURU KIKUCHI and published by International Atomic Energy. This book was released on 2002-01-01 with total page 1158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Humans do not live by bread alone. Physically we are puny creatures with limited prowess, but with unlimited dreams. We see a mountain and want to move it to carve out a path for ourselves. We see a river and want to tame it so that it irrigates our fields. We see a star and want to fly to its planets to secure a future for our progeny. For all this, we need a genie who will do our bidding at a flip of our fingers. Energy is such a genie. Modern humans need energy and lots of it to live a life of comfort. In fact, the quality of life in different regions of the world can be directly correlated with the per capita use of energy [1.1–1.5]. In this regard, the human development index (HDI) of various countries based on various reports by the United Nations Development Programme (UNDP) [1.6] (Fig. 1.1), which is a parameter measuring the quality of life in a given part of the world, is directly determined by the amount of per capita electricity consumption. Most of the developing world (~5 billion people) is crawling up the UN curve of HDI versus per capita electricity consumption, from abysmally low values of today towards the average of the whole world and eventually towards the average of the developed world. This translates into a massive energy hunger for the globe as a whole. It has been estimated that by the year 2050, the global electricity demand will go up by a factor of up to 3 in a high growth scenario [1.7–1.9]. The requirements beyond 2050 go up even higher.
Download or read book Zonal Jets written by Boris Galperin and published by Cambridge University Press. This book was released on 2019-02-28 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a comprehensive, multidisciplinary volume on the physics of zonal jets, from the leading experts, for graduate students and researchers.
Download or read book Zonal Jets written by Boris Galperin and published by Cambridge University Press. This book was released on 2019-02-28 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades, great progress has been made in our understanding of zonal jets across many subjects - atmospheric science, oceanography, planetary science, geophysical fluid dynamics, plasma physics, magnetohydrodynamics, turbulence theory - but communication between researchers from different fields has been weak or non-existent. Even the terminology in different fields may be so disparate that researchers working on similar problems do not understand each other. This comprehensive, multidisciplinary volume will break cross-disciplinary barriers and aid the advancement of the subject. It presents a state-of-the-art summary of all relevant branches of the physics of zonal jets, from the leading experts. The phenomena and concepts are introduced at a level accessible to beginning graduate students and researchers from different fields. The book also includes a very extensive bibliography.
Download or read book Size Scaling of Turbulent Transport in Magnetically Confined Plasmas written by Zhihong Lin and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulent Transport In Magnetized Plasmas Second Edition written by C Wendell Horton, Jr and published by #N/A. This book was released on 2017-07-21 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a few seconds with large machines, scientists and engineers have now created the fusion power of the stars in the laboratory and at the same time find the rich range of complex turbulent electromagnetic waves that transport the plasma confinement systems. The turbulent transport mechanisms created in the laboratory are explained in detail in the second edition of 'Turbulent Transport in Magnetized Plasmas' by Professor Horton.The principles and properties of the major plasma confinement machines are explored with basic physics to the extent currently understood. For the observational laws that are not understood — the empirical confinement laws — offering challenges to the next generation of plasma students and researchers — are explained in detail. An example, is the confinement regime — called the 'I-mode' — currently a hot topic — is explored.Numerous important problems and puzzles for the next generation of plasma scientists are explained. There is growing demand for new simulation codes utilizing the massively parallel computers with MPI and GPU methods. When the 20 billion dollar ITER machine is tested in the 2020ies, new theories and faster/smarter computer simulations running in near real-time control systems will be used to control the burning hydrogen plasmas.
Download or read book Rossby Wave Drift Wave and Zonal Flow Turbulence written by Brenda E. Quinn and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An extensive qualitative and quantitative study of Rossby wave, drift wave and zonal flow turbulence in the Charney-Hasegawa-Mima model is presented. This includes details of two generation mechanisms of the zonal flows, evidence of the nonlocal nature of this turbulence and of the energy exchange between the small and large scales. The modulational instability study shows that for strong primary waves the most unstable modes are perpendicular to the primary wave, which corresponds to the generation of a zonal flow if the primary wave is purely meridional. For weak waves, the maximum growth occurs for off-zonal modulations that are close to being in three-wave resonance with the primary wave. Nonlinear jet pinching is observed for all nonlinearity levels but the subsequent dynamics differ between strong and weak primary waves. The jets of the former further roll up into Kármán-like vortex streets and saturate, while for the latter, the growth of the unstable mode reverses and the system oscillates between a dominant jet and a dominant primary wave. A critical level of nonlinearity is defined which separates the two regimes. Some of these characteristics are captured by truncated models. Numerical proof of the extra invariant in Rossby and drift wave turbulence is presented. While the theoretical derivations of this invariant stem from the wave kinetic equation which assumes weak wave amplitudes, it is shown to be relatively-well conserved for higher nonlinearities also. Together with the energy and enstrophy, these three invariants cascade into anisotropic sectors in the k-space as predicted by the Fjørtoft argument. The cascades are characterised by the zonostrophy pushing the energy to the zonal scales. A small scale instability forcing applied to the model has demonstrated the wellknown drift wave - zonal flow feedback loop. The drift wave turbulence is generated from this primary instability. The zonal flows are then excited by either one of the generation mechanisms, extracting energy from the drift waves as they grow. Eventually the turbulence is completely suppressed and the zonal flows saturate. The turbulence spectrum is shown to diffuse in a manner which has been mathematically predicted. The insights gained from this simple model could provide a basis for equivalent studies in more sophisticated plasma and geophysical fluid dynamics models in an effort to fully understand the zonal flow generation, the turbulent transport suppression and the zonal flow saturation processes in both the plasma and geophysical contexts.
Download or read book The Role of Zonal Flows and Predator prey Oscillations in Triggering the Formation of Edge and Core Transport Barriers written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we present direct evidence of low frequency, radially sheared, turbulence-driven flows (zonal flows (ZFs)) triggering edge transport barrier formation preceding the L- to H-mode transition via periodic turbulence suppression in limit-cycle oscillations (LCOs), consistent with predator-prey dynamics. The final transition to edge-localized mode-free H-mode occurs after the equilibrium E × B flow shear increases due to ion pressure profile evolution. ZFs are also observed to initiate formation of an electron internal transport barrier (ITB) at the q = 2 rational surface via local suppression of electron-scale turbulence. Multi-channel Doppler backscattering (DBS) has revealed the radial structure of the ZF-induced shear layer and the E × B shearing rate, [omega]E×B, in both barrier types. During edge barrier formation, the shearing rate lags the turbulence envelope during the LCO by 90°, transitioning to anti-correlation (180°) when the equilibrium shear dominates the turbulence-driven flow shear due to the increasing edge pressure gradient. The time-dependent flow shear and the turbulence envelope are anti-correlated (180° out of phase) in the electron ITB. LCOs with time-reversed evolution dynamics (transitioning from an equilibrium-flow dominated to a ZF-dominated state) have also been observed during the H-L back-transition and are potentially of interest for controlled ramp-down of the plasma stored energy and pressure (normalized to the poloidal magnetic field) $\beta_{\theta} =2\mu_{0} n{({T_{{\rm e}} +T_{{\rm i}}})}/{B_{\theta}^{2}}$ in ITER.
Download or read book Turbulent Transport Reduction by Zonal Flows written by Zhihong Lin and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Spreading Into Linearly Stable Zone and Transport Scaling written by Taik Soo Hahm and published by . This book was released on 2003 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Self organized Turbulent Transport in Fusion Plasmas written by Claudia Norscini and published by . This book was released on 2015 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transport barriers (TB) are a key element in controlling turbulent transport and achieving high performance burning plasmas. Theoretical studies are addressing the turbulence self-regulation as a possible explanation for transport barrier formation but a complete understanding of such complex dynamics is still missing. In this context, we address self-organized turbulent transport in fusion plasmas with the aim of presenting a novel understanding of transport barriers dynamics. The numerical tools we use span simulations from the most complex gyrokinetic turbulence to simpler 2D fluid turbulence and predator-prey like models.Two features of self-organizations, avalanches and zonal flows (ZFs), appear to control large scale transport. In the SOL (Scrape Off Layer) , intermittent avalanche events do not allow for time or space scale separation between mean fields and fluctuation terms. In the edge, the generation of long living double shear layers in the profiles of the velocity reduces radial turbulent transport. Such radially distributed barriers govern profile corrugations. A 2D turbulent model for pedestal generation, which is not specific of Tokamak plasmas, has been developed, the pedestal being localized at the interface between regions with different zonal flow damping: the edge region, where zonal flows are weakly damped by collisions, and the SOL region characterized by zonal flow damping due to boundary conditions. Quasi-periodic relaxation events are studied reducing the model to three modes coupling to identify the interplay between streamers and ZFs and the role of Reynolds stress in the generation and saturation of TBs.
