Rozprawy doktorskie na temat „Transport de turbulence”
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Irvine, Mark Rankin. "Turbulence and turbulent transport above and within coniferous forests". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240324.
Pełny tekst źródłaNewton, Andrew P. L. "Transport in sheared turbulence". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531179.
Pełny tekst źródłaLaenen, François. "Modulation de mélange, transport et turbulence dans des suspensions solides : étude et modélisation". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4010/document.
Pełny tekst źródłaThe transport of particles by turbulent flows is ubiquitous in nature and industry. It occurs in planet formation, plankton dynamics and combustion in engines. For the dispersion of atmospheric pollutants, traditional predictive models based on eddy diffusivity cannot accurately reproduce high concentration fluctuations, which are of primal importance for ecological and health issues. The first part of this thesis relates to the dispersion by turbulence of tracers continuously emitted from a point source. Mass fluctuations are characterized as a function of the distance from the source and of the observation scale. The combination of various physical mixing processes limits the use of fractal geometric tools. An alternative approach is proposed, allowing to interpret mass fluctuations in terms of the various regimes of pair separation in turbulent flows. The second part concerns particles with a finite and possibly large inertia, whose dispersion in velocity requires developing efficient modelling techniques. A novel numerical method is proposed to express inertial particles distribution in the position-velocity phase space. Its convergence is validated by comparison to Lagrangian measurements. This method is then used to describe the modulation of two-dimensional turbulence by large-Stokes-number heavy particles. At high inertia, the effect is found to be analogous to an effective large-scale friction. At small Stokes numbers, kinetic energy spectrum and nonlinear transfers are shown to be modified in a non-trivial way which relates to the development of instabilities at vortices boundaries
Briard, Antoine. "Modélisation du transport en turbulence homogène". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066201/document.
Pełny tekst źródłaModelling is essential to understand and reproduce the dominant physical mechanisms occurring in natural turbulent flows such as atmospheric and oceanic ones. Indeed, the dynamics of geophysical flows results of multiple complex processes interacting with each others, at various scales, intensities, and on different characteristic times. The fine description of such flows is currently out of reach of direct numerical simulations, notably because of Reynolds numbers limitations. Consequently, we address in this thesis the modelling of homogeneous turbulence, using the spectral formalism of the eddy-damped quasi-normal Markovian (EDQNM) approximation. This first allows us to obtain results rapidly in terms of computational resources at very large Reynolds numbers, and thus to investigate separately some of the fundamental mechanisms at stake in natural turbulent flows, namely shear, mean temperature gradient, stratification, helicity, and combinations of these processes. In this framework, a two-step approach is considered: first, EDQNM is used to close the non-linear terms in the second-order moments equations, and anisotropy is then modelled through spherically-averaged tensors. This methodology is applied to the various configurations mentioned above, permits to propose new theoretical results, and to assess them numerically at large Reynolds numbers. Among the most important findings, we focused on (i) the prediction of the decay and growth laws of crucial one-point statistics such as the kinetic energy, the scalar variance, and helicity; (ii) the determination of spectral scalings; and (iii) the scale by scale distribution of anisotropy
Raus, David. "Transport sédimentaire sur rugosités immobiles : de l'hydrodynamique locale à la morphodynamique". Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/23587/1/Raus_David.pdf.
Pełny tekst źródłaJermyn, Adam Sean. "Turbulence and transport in stars and planets". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278021.
Pełny tekst źródłaDonnel, Peter. "Impurity transport in tokamak plasmas : gyrokinetic study of neoclassical and turbulent transport". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0485/document.
Pełny tekst źródłaImpurity transport is an issue of utmost importance for tokamaks. Indeed high-Z materials are only partially ionized in the plasma core, so that they can lead to prohibitive radiative losses even at low concentrations, and impact dramatically plasma performance and stability. On-axis accumulation of tungsten has been widely observed in tokamaks.While the very core impurity peaking is generally attributed to neoclassical effects, turbulent transport could well dominate in the gradient region at ITER relevant collisionality. Up to recently, first principles simulations of corresponding fluxes were performed with different dedicated codes, implicitly assuming that both transport channels are separable and therefore additive. The validity of this assumption is questionned. Simulations obtained with the gyrokinetic code GYSELA have shown clear evidences of a neoclassical-turbulence synergy for impurity transport and allowed the identification of a mechanism that underly this synergy.An analytical work allows to compute the level and the structure of the axisymmetric part of the electric potential knowing the turbulence intensity. Two mechanisms are found for the generation of poloidal asymmetries of the electric potential: flow compressibility and the ballooning of the turbulence. A new prediction for the neoclassical impurity flux in presence of large poloidal asymmetries and pressure anisotropies has been derived. A fair agreement has been found between the new theoretical prediction for neoclassical impurity flux and the results of a GYSELA simulation displaying large poloidal asymmetries and pressure anisotropies induced by the presence of turbulence
Cohet, Romain. "Transport des rayons cosmiques en turbulence magnétohydrodynamique". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS051/document.
Pełny tekst źródłaIn this thesis, we study the transport properties of high energy charged particles in turbulent electromagnetic fields.These fields were generated by using the magnetohydrodynamic (MHD) code RAMSES, which solve the compressible ideal MHD equations. We have developed a module for generating the MHD turbulence, by using a large scale forcing technique. The MHD equations induce a cascading of the energy from large scales to small ones, developing an energy spectrum which follows a power law, called the inertial range.We have developed a module for computing the charged particle trajectories once the turbulent spectrum is established. By injecting the particles to energy such as the inverse of the particle Larmor radius corresponds to a mode in the inertial range of the Fourier spectrum, we have highlighted systematic effects related to the power law spectrum. This method showed that the mean free path is independent of the particules energy until the Larmor radius takes values close to the turbulence coherence scale. The dependence of the mean free path with the alfvénic Mach number produced a power law.We have also developed a technique to measure the anisotropy effect of the MHD turbulence in the cosmic rays transport properties through the calculation of local magnetic fields. This study has shown an effect on the pitch angle scattering coefficient, which confirmed the assumption that the particles are more sensitive to changes in small scales fluctuations
黎敦楠 i Tun-nam Lai. "Turbulent transport of airborne pollutant near a low hill". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31227491.
Pełny tekst źródłaTeaca, Bogdan. "Numerical simulations of transport processes in magnetohydrodynamic turbulence". Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210082.
Pełny tekst źródłaL’objectif principal de cette thèse est d’analyser le transport d’énergie inter-échelles en utilisant une simulation numérique directe d’un écoulement turbulent MHD. Les propriétés de localité du transport de l’énergie entre les échelles pour un écoulement anisotropique ou isotropique, généré par la présence d’un champ magnétique constant, sont renforcées. Un objectif secondaire est d’établir un cadre de travail pour l’étude du transport de particules test chargées dans un champ électromagnétique turbu-lent, i.e. généré par le mouvement d’un fluide conducteur, qui possède des structures à plusieurs ordres de grandeur. La structure de la thèse est présentée ci-dessous.
Dans la première partie, composée des deux premiers chapitres, l’auteur présente les notions de turbu-lences, aussi bien hydrodynamiques que MHD. Ces deux chapitres sont des synthèses.
La deuxième partie est la principale source de nouveaux résultats. Le chapitre 3 présente les méthodes numériques pour la résolution des équations, les méthodes pseudo-spectrales. Un nouveau type de force est introduit, imposant un niveau de dissipation pour tous les invariants. Dans le chapitre 4, il est effectué une analyse du transfert d'énergie entre ordres de grandeur pour les turbulences MHD. Pour explorer ces transferts d'énergie, le domaine spectral est décomposé en une série de coques de même nombre d'onde. Le transfert moyen d'énergie entre ces coques est analysé. Les transferts d'énergie s'avèrent être surtout locaux en ordre de grandeur, alors qu'une contribution non locale existe due à la force. En présence d'un champ magnétique, l'écoulement développe une direction préférentielle, une anisotropie, où une idée nouvelle de décomposition de l'espace spectral en structures annulaires est présentée. Utilisant cette décomposition annulaire on trouve que le transfert entre anneaux est local, surtout dans les anneaux de direction perpendiculaire au champ magnétique. Pour les turbulences isotropiques, dans le chapitre 5, la localité des flux d'énergie est explorée par le biais de fonctions de localité. Dans le cas de la turbulence MHD, nous avons un comportement non local plus prononcé.
La dernière partie, les chapitres 6 et 7, présente le formalisme de suivi des trajectoires de particules chargées évoluant dans un champ électromagnétique turbulent. L'influence de la méthode d'interpola-tion du solveur de particules est étudiée avant la présentation des concepts liés au transport de particu-les et aux régimes de diffusion. L'adiabatisme du mouvement des particules chargées est discuté et le transport de particules chargées dans un champ magnétique turbulent est montré en exemple.
Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished
Hornsby, William Anestis. "Kinetic simulation of plasma transport in magnetic turbulence". Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497934.
Pełny tekst źródłaYang, Qingjun (Judy Qingjun). "Impacts of vegetation-generated turbulence on sediment transport". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120638.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 179-188).
Aquatic vegetated habitats, including wetlands and mangroves, are disappearing at an annual rate of 1 to 7%. These ecosystems provide habitats important to fisheries, enhance water quality by filtering nutrients from run-off, and also protect coastal regions from storm surges and waves. To mitigate the loss of these habitats, restoration projects import sediment to eroded areas. The success of the restoration depends on its ability to retain sediment; therefore restoration design requires a good understanding of sediment transport within vegetated landscapes. However, there is currently no quantitative model for sediment transport in vegetated regions, and many restoration projects have failed due to unanticipated erosion from the restored regions. The goal of this thesis is to develop a predictive model for sediment transport in regions with vegetation. First, the affect of vegetation on the critical condition when sediment start to move was explored. To identify the critical condition, an imaging system was designed to track the trajectories of individual moving grain through running water. The critical flow velocity (U[subscript crit]) above which sediment starts to move was identified from the tracked sediment trajectories for both bare (non-vegetated) and vegetated regions. The experimental results showed that for the same type of sediment, U[subscript crit] decreased with increasing vegetation solid volume fraction. This was attributed to the vegetation-generated turbulence, which induced a local, vertical, adverse pressure, or a lift force on the sediment grain, facilitating sediment transport. In contrast, the turbulent kinetic energy (k[subscript t]) was found to be roughly a constant at the critical condition for different vegetation volume fractions, suggesting that k[subscript t] is a more universal metric than T for predicting the critical condition of the sediment transport. A k[subscript t]-based model was developed to predict U[subscript crit] for channels with different vegetation solid volume fractions. The turbulence-based model successfully predicted U[subscript crit] for both bare and vegetated channels, providing a useful tool for ecologists to predict whether a vegetated landscape will erode or not. Second, the impact of vegetation on the bed load transport rate was explored. A system that allows sediment to be bypassed, a cart to distribute sediment, a method that measures the dry weight of wet sand without drying the sediment, a topography system, and an sediment trajectory imaging system were designed. The bed load transport rate (Q[subscript s],) was measured for both bare channels and channels with different vegetation solid volume fractions ([phi]) under different flow rates. At the same [tau], the measured Q[subscript s], increased with increasing [phi], suggesting that vegetation-generated turbulence, which also increased with increasing ]phi], was augmenting the bed load transport. At the same near-bed turbulent kinetic energy, k[subscript t], the Q[subscript s], measured in both bare and vegetated channels agreed within uncertainty, suggesting that k[subscript t] may be a more universal predictor of Q[subscript s] than [tau]. The Einstein-Brown [tau]-based bed load transport model was reinterpreted as a k[subscript t]-based model. The new kt-based model predicted the Q[subscript s] measurements for both bare and vegetated channels. The dependence of Q[subscript s] on k[subscript t] was explained by the statistics of individual grain motion, which showed that Q[subscript s] was predominantly controlled by the number of grains in motion, which correlated with k[subscript t]. The proposed k[subscript t]-based sediment transport model can be used to simulate large-scale landscape evolution and to help ecologists design better coastal restoration strategies. Third, the impacts of vegetation on bed-form characteristics and migration rate were studied. After the measured bed load transport rate converged to an equilibrium value, the bed topography was scanned by a laser topography system. Bed-forms with height less than 2cm were observed and characterized as ripples. For low vegetation solid volume fraction ([phi] by Qingjun Judy Yang.
Ph. D.
Nagata, Koji. "TURBULENCE STRUCTURE AND TRANSPORT PHENOMENA IN DENSITY STRATIFICATION". Kyoto University, 2000. http://hdl.handle.net/2433/151546.
Pełny tekst źródłaPlasting, Stephen Christopher. "Turbulence has its limits : a priori estimates of transport properties in turbulent fluid flows". Thesis, University of Bristol, 2004. http://hdl.handle.net/1983/ca76fd77-e2a3-4eed-8a34-39203e11c84f.
Pełny tekst źródłaDonnel, Peter. "Impurity transport in tokamak plasmas : gyrokinetic study of neoclassical and turbulent transport". Electronic Thesis or Diss., Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0485.
Pełny tekst źródłaImpurity transport is an issue of utmost importance for tokamaks. Indeed high-Z materials are only partially ionized in the plasma core, so that they can lead to prohibitive radiative losses even at low concentrations, and impact dramatically plasma performance and stability. On-axis accumulation of tungsten has been widely observed in tokamaks.While the very core impurity peaking is generally attributed to neoclassical effects, turbulent transport could well dominate in the gradient region at ITER relevant collisionality. Up to recently, first principles simulations of corresponding fluxes were performed with different dedicated codes, implicitly assuming that both transport channels are separable and therefore additive. The validity of this assumption is questionned. Simulations obtained with the gyrokinetic code GYSELA have shown clear evidences of a neoclassical-turbulence synergy for impurity transport and allowed the identification of a mechanism that underly this synergy.An analytical work allows to compute the level and the structure of the axisymmetric part of the electric potential knowing the turbulence intensity. Two mechanisms are found for the generation of poloidal asymmetries of the electric potential: flow compressibility and the ballooning of the turbulence. A new prediction for the neoclassical impurity flux in presence of large poloidal asymmetries and pressure anisotropies has been derived. A fair agreement has been found between the new theoretical prediction for neoclassical impurity flux and the results of a GYSELA simulation displaying large poloidal asymmetries and pressure anisotropies induced by the presence of turbulence
Guichardaz, Robin. "Shape dynamics and clustering processes of particles transported by turbulent flows : a stochastic approach". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN027/document.
Pełny tekst źródłaThis thesis deals with the dynamics of particles in turbulent flows and the formation of structures. Two physical situations are studied. First, we consider the dynamics of tracers, that is ideal fluid particles, transported by a turbulent velocity field. A triplet of such particles forms a triangle, which tends to be flattened under the action of the incompressible flow. Second, inertial particles of density higher than that of the fluid and subjected to a viscous drag force usually cluster on regions of high concentration, leading to the formation of strange attractors. The approach followed in this thesis consists in modeling the action of the turbulent flow using tools of stochastic dynamics (such as Langevin equations), which allow us to obtain a effective description of these phenomena. For inertial particles, the attractors are characterized by a non-integer fractal dimension. The addition of an external noise in the equations of motion lead to a generalization of this notion to negative values, intrinsic to the dynamics in the absence of noise. This thesis shows that it is possible to formulate the two problems in terms of very general stochastic processes, whose prototype is the one describing the sedimentation of particles in the presence of a thermal noise. The determination of the characteristics of the solution requires a new approach. The solution proposed here is based on the large deviation theory
Baschetti, Serafina. "A new modelling of the cross-field transport in diverted edge plasma : application to 2D transport simulations with SolEdge2D-EIRENE". Electronic Thesis or Diss., Ecole centrale de Marseille, 2019. http://www.theses.fr/2019ECDM0009.
Pełny tekst źródłaSteady-state operations of the next-generation fusion device ITER will require the development of reliable numerical tools to estimate key engineering parameters suitable for technological constraints at reasonable computational cost.So-called transport codes fulfil this requirement since they rely on 2D fluid equations averaged over time fluctuations, similarly to Reynolds Averaged Navier-Stokes models commonly used for engineering applications in the neutral fluid community. Furthermore, transport codes can gather most of the physical ingredients ruling the edge plasma behaviour, as well as realistic magnetic topology and wall geometry. However, their predictability is limited by a crude description of turbulent fluxes perpendicular to the magnetic field lines. In the plasma community, a special concern is devoted to acquire a detailed understanding of these fluxes, since they strongly impact on the power extraction and the confinement of plasma over extended periods of time. In transport codes though, turbulent fluxes, which are assumed diffusive, are crudely determined by either homogeneous, or ad-hoc diffusive coefficients, or feedback-loop procedures applied a-posteriori on experimental data.Motivated by these issues, in this work we introduce step-by-step a new approach with the aim to self-consistently estimate the distribution of turbulent fluxes in transport codes, when steady-state plasmas are concerned. The underlying strategy is inspired by the work done from the 60’s in neutral turbulence and adapted here to plasma for fusion applications.The first key concept is the Boussinesq assumption. It consists in assuming a colinearity between the Reynolds stress tensor - which represents the contribution of turbulence to the mean flow - and the mean rate of strain tensor - expressed by the gradient of the mean velocity through a coefficient: the so-called eddy-viscosity. The second concept is to express this new eddy viscosity coefficient as a function of characteristic turbulence quantities. We have focused here on the most popular in Computational Fluid Dynamics, the κ-ε model, where transport equations for the averaged kinetic turbulent energy and the turbulence dissipation rate are designed semi-empirically. Steady-state κ and ε allow for a self-consistent estimation of the eddy-viscosity coefficient, thus including the impact of turbulence in steady-state mean flows. We propose a κ-ε -like model where two transport equations for turbulent kinetic energy and its dissipation rate are derived algebraically, including the physics of the linear interchange instability. For the numerical implementation, we exploit the flexibility of the transport package SolEdge2D-EIRENE, developed for many years through the collaboration of the IRFM at the CEA and the laboratory M2P2 at Aix-Marseille University.Since the new model is semi-empirical, it presents some free parameters to be closed. In this work, we have proposed different approaches. In particular, in order to increase the predictive capabilities of the model, a reference scaling law for the width of the heat-flux profile in the scrape-off layer has been assumed, empirically determined from the experimental measurements of the outer target heat load in various machines. The new model is integrated in SolEdge2D-EIRENE for simulations with diverted plasma in TCV and WEST-like geometries, for L-mode discharges. Steady-state results are discussed and shown to favourably compare with experimental data at both the outer mid-plane and the outer divertor. Moreover, self-consistent distributions of diffusivities are shown to exhibit poloidal asymmetries consistently with the ballooned distribution of cross-field transport due to the interchange instability and observed at the same conditions in both first-principle codes and experiments
Tisserand, Jean-Christophe. "Convection thermique : transport et mélange". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2010. http://tel.archives-ouvertes.fr/tel-00612953.
Pełny tekst źródłaBian, Nicolas. "Turbulence convective et transport intermittent dans un plasma magnétisé". Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11012.
Pełny tekst źródłaFutatani, Shinpei. "Multiscaling Analysis of Impurity Transport in Drift Wave Turbulence". Kyoto University, 2008. http://hdl.handle.net/2433/123882.
Pełny tekst źródła0048
新制・課程博士
博士(エネルギー科学)
甲第14180号
エネ博第182号
新制||エネ||42(附属図書館)
UT51-2008-N497
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 近藤 克己, 教授 岸本 泰明, 教授 前川 孝
学位規則第4条第1項該当
Garbet, Xavier. "Turbulence et transport anormal dans les plasmas de Tokamak". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37613789t.
Pełny tekst źródłaWang, Eric Hut-Jun. "Gyrokinetic effects on transport and electron temperature gradient turbulence". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1835511811&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Pełny tekst źródłaPessah, Martin Elias. "Magnetohydrodynamic Turbulence and Angular Momentum Transport in Accretion Disks". Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194324.
Pełny tekst źródłaGodeferd, Fabien. "Introduction d'une partition ondes-turbulence dans les modèles de transport pour les écoulements turbulents stablement stratifiés". Ecully, Ecole centrale de Lyon, 1994. http://www.theses.fr/1994ECDL0027.
Pełny tekst źródłaIn this work, incompressible homogeneous turbulence with a stable stratification is studied. The approach consists mainly in a statistical two-point closure model of EDQNM type, for Eddy Damped Quasi Normal Markovian, presented in a general way. Using an axisymmetric configuration, the model is based on a decomposition of the fluctuating velocity field on the eigenmodes of the linearized Boussinesq equations, namely the stationary, horizontally rotational, vortex mode, and the propagating irrotational internal waves. Different non linear transfer terms are identified, corresponding to specific interactions between triads of eigenmodes, and the resonant contributions are investigated. The influence of stratification is brought to light through spectral indicators of the directivity, and the polarization anisotropy and in physical space through the computation of integral length scales with vertical and horizontal separation. By means of kinematic simulations, the vertically decorrelated layers in the turbulent field are shown. Moreover, the properties of internal gravity waves allow a close comparison with the geostrophic aproximation for geophysical flows and with a triadic stability analysis. The problem of diffusion of an initially isotropic energy spectrum through a weak inhomogeneous interface is adressed by means of an analytical solution in the linear limit. Finally, the statistical two-point model is compared to a one-point one (Craft & Launder transport model) through correlation terms involving the pressure, with the velocity field and the temperature field
Strugarek, Antoine. "Turbulence, transport et confinement : des tokamaks au magnétisme des étoiles". Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://tel.archives-ouvertes.fr/tel-00765706.
Pełny tekst źródłaBuchholz, Rico [Verfasser], i Arthur [Akademischer Betreuer] Peeters. "Momentum Transport in Gyrokinetic Turbulence / Rico Buchholz ; Betreuer: Arthur Peeters". Bayreuth : Universität Bayreuth, 2016. http://d-nb.info/1117646351/34.
Pełny tekst źródłaColyer, Greg J. "Gyrokinetic turbulence and transport in the Mega Ampere Spherical Tokamak". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:0146f522-42a9-4f1f-806a-9ccbfcf3379e.
Pełny tekst źródłaStrugarek, Antoine. "Turbulence, transport et confinement : des tokamaks à la tachocline solaire". Paris 7, 2012. http://www.theses.fr/2012PA077204.
Pełny tekst źródłaThis thesis is part of the general study of self-organization in hot and magnetized plasmas. We focus our work on two specific objects : stars and tokamaks. We use first principle numerical simulations to study turbulence, transport and confinement in these plasmas. The first part of this thesis introduces the main characteristics of stellar and tokamak plasmas. The reasons for studying them together are properly detailed. The second part is focused on stellar aspects. We study the interactions between the 3D turbulent motions in the solar convection zone with an internal magnetic field in the tachocline (the transition region between the instable and stable zones in the Sun). The tachocline is a very thin layer (less than five percent of the solar radius) that acts as a transport barrier of angular momentum. We show that such an internal magnetic field is not likely to explain the observed thickness of the tachocline and we give some insights on how to find alternative mecanisms to constrain it. We also explore the effect of the environment of star on its structure. We develop a methodology to study the influence of stellar wind and of the magnetic coupling of a star with its orbiting planets. We use the same methodology to analyse the magnetic interaction between a stellar wind and a planetary magnetosphere that acts as a transport barrier of matter. Then, the third part is dedicated to fusion oriented research. We present a numerical investigation on the experimental mecanisms that lead to the development of transport barriers in the plasma. These barriers are particularly important for the design of high performance fusion devices. The creation of transport barriers is obtained in turbulent first principle simulations for the very first time. The collaboration between the two scientific teams lead to the results presented in the fourth part of this thesis. An original spectral method is developed to analyse the saturation of stellar convective dynamos and of the ion temperature gradient instability. We also develop a reduced model that tackles the interaction between turbulent motions, waves, and zonal and mean flows. The same model is applied to both the solar tachocline and tokamak turbulence, putting forth the strong analogy that exists between the two objects we studied
Takeda, Kazuo. "Intermittent thermal transport generated by ion temperature gradient driven turbulence". Kyoto University, 2004. http://hdl.handle.net/2433/145253.
Pełny tekst źródła0048
新制・課程博士
博士(エネルギー科学)
甲第11120号
エネ博第98号
新制||エネ||27(附属図書館)
22670
UT51-2004-L917
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 近藤 克己, 教授 前川 孝, 助教授 中村 祐司
学位規則第4条第1項該当
Chôné, Laurent. "Turbulence, flows and transport barriers at the tokamak plasma edge". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4701.
Pełny tekst źródłaThe topic of this thesis is the interaction between turbulence and flows at the tokamak edge, and their influence on the confinement. Turbulence is the main contribution to the outward transport in magnetic fusion devices, and a strong limiting factor for their performance. It can be stabilised by flows, through shear-mediated decorrelation of convective cells, and through non-linear coupling. Strong shear flows causing a localised reduction of transport (transport barrier) are often observed in experiments, and several regimes of improved confinement such as the High-confinement mode are accessed routinely. There is a growing body of evidence from experiments showing that the mean flow responsible for the barrier is governed by force balance, while non-linear interplay between turbulence, turbulence-driven zonal-flows, and the mean flow occurs during the transition phase. In this thesis, we extend a fluid model for plasma edge turbulence to include collisional relaxation of flows towards force. We show that accounting for a contribution of neoclassical allows for the spontaneous formation of a transport barrier to occur in flux-driven simulation. Dynamical features reminiscent of the L-H transition and H-mode are recovered, such as relaxation-oscillations of the barrier and dithering of the radial electric field during the barrier formation. An analysis is carried out to identify the roles of zonal-flows and force balance during the transition, and it is found that in our simulations that zonal flows provide temporary quenching of the turbulence via non-linear coupling, allowing for the mean flow to grow and form the barrier
Chôné, Laurent. "Turbulence, flows and transport barriers at the tokamak plasma edge". Electronic Thesis or Diss., Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4701.
Pełny tekst źródłaThe topic of this thesis is the interaction between turbulence and flows at the tokamak edge, and their influence on the confinement. Turbulence is the main contribution to the outward transport in magnetic fusion devices, and a strong limiting factor for their performance. It can be stabilised by flows, through shear-mediated decorrelation of convective cells, and through non-linear coupling. Strong shear flows causing a localised reduction of transport (transport barrier) are often observed in experiments, and several regimes of improved confinement such as the High-confinement mode are accessed routinely. There is a growing body of evidence from experiments showing that the mean flow responsible for the barrier is governed by force balance, while non-linear interplay between turbulence, turbulence-driven zonal-flows, and the mean flow occurs during the transition phase. In this thesis, we extend a fluid model for plasma edge turbulence to include collisional relaxation of flows towards force. We show that accounting for a contribution of neoclassical allows for the spontaneous formation of a transport barrier to occur in flux-driven simulation. Dynamical features reminiscent of the L-H transition and H-mode are recovered, such as relaxation-oscillations of the barrier and dithering of the radial electric field during the barrier formation. An analysis is carried out to identify the roles of zonal-flows and force balance during the transition, and it is found that in our simulations that zonal flows provide temporary quenching of the turbulence via non-linear coupling, allowing for the mean flow to grow and form the barrier
Bec, Jérémie. "Particules, singularités et turbulence". Paris 6, 2002. http://www.theses.fr/2002PA066027.
Pełny tekst źródłaManas, Pierre. "Gyrokinetic simulations of turbulent impurity transport in tokamaks". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4745/document.
Pełny tekst źródłaUnderstanding impurity transport in the core of tokamak plasmas is central to achieving controlled fusion. Indeed impurities are ubiquitous in these devices and their presence in the core are detrimental to plasma confinement (fuel dilution, Bremsstrahlung). Recently, specific attention was given to the convective mechanism related to the gradient of the toroidal rotation to explain experimental flat/hollow impurity profiles in the plasma core. In this thesis, up-to-date modelling tools (NEO for neoclassical transport and GKW for turbulent transport) including the impact of toroidal rotation are used to study both the neoclassical and turbulent contributions to impurity fluxes. A comparison of the experimental and modelled carbon density peaking factor (R/LnC) is performed for a large number of baseline and hybrid H-mode plasmas (increased confinement regimes) with modest to high toroidal rotation from the European tokamak JET. Confrontation of experimental and modelled carbon peaking factor yields two main results. First roto-diffusion is found to have a nonnegligible impact on the carbon peaking factor at high values of the toroidal rotation frequency gradient. Second, there is a tendency to overpredict the experimental R/LnC in the core inner region where the carbon density profiles are hollow. This disagreement between experimental and modelled R/LnC, closely related to the collisionality, is also observed for the momentum transport channel which hints at a common parallel symmetry breaking mechanism lacking in the simulations
Lecouturier, Magali. "Turbulence and macro-turbulence in the bottom boundary layer downstream of large-scale bedforms; implications for sediment transport". Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42129/.
Pełny tekst źródłaNorscini, Claudia. "Self-organized turbulent transport in fusion plasmas". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4076.
Pełny tekst źródłaTransport 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
Cziegler, István. "Turbulence and transport phenomena in edge and scrape-off-layer plasmas". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/77484.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (p. 171-178).
This thesis reports recent experimental studies of edge turbulence structure using gas-puff-imaging at high time resolution in a radially broad zone at the low-field-side of Alcator C-Mod[1], and highlights the connections between its characteristics and particle transport. Within the framework of this thesis a new detector system has been designed and built for viewing the steep gradient outboard midplane region at minor radii 0.9 < r/rma, < 1.1, where turbulence is postulated to be driven [2, 3]. The design is optimized for the study of edge and scrape-off-layer turbulence, based on previous studies of these regions. Analysis of the data from this diagnostic in Ohmic L-modes from the electron diamagnetic drift propagating turbulence in the closed field line region of the plasma edge shows a strong scaling of the fluctuation power 5/n with the density normalized to the tokamak density limit ne/ng; in addition, a critical physical scale is found at ... ~ 0.1, where the critical wavenumber is normalized to ps, the ion Larmor radius at the sound speed, also known as the drift scale. The characteristic size scale shows very little variation with operating parameters. The analysis of the physical scale includes spectral analysis, yielding robust spectral indices beta= ~4.5 for larger wavenumbers and a sensitive spectral shape for lower wavenumbers, and the first spectral transfer measurement of turbulence on C-Mod, showing that the critical scale feeds power into the turbulence. A connection is found to the quasi-coherent mode (QCM), a modelike edge fluctuation characteristic of the Enhanced D-Alpha H-mode, which also appears at ... ~ 0.1 and has decreased inverse transfer but greatly enhanced forward transfer compared to the L-mode levels.
by István Cziegler.
Ph.D.
Daris, Thomas. "Étude des modèles de turbulence à quatre équations de transport pour la prévision des écoulements turbulents faiblement chauffés". Toulouse, ENSAE, 2002. http://www.theses.fr/2002ESAE0017.
Pełny tekst źródłaSun, Peng, i Peng Sun. "Charged-Particle Transport in Turbulent Magnetic Fields". Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621573.
Pełny tekst źródłaGabbaï, Philippe. "Instabilités, auto-organisation et transport dans la turbulence d'ondes de dérive dissipatives". Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11039.
Pełny tekst źródłaVedula, Prakash. "Study of scalar transport in turbulent flows using direct numerical simulations". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12119.
Pełny tekst źródłaFuttersack, Romain. "Modélisation fluide du transport magnétisé dans les plasmas froids". Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2537/.
Pełny tekst źródłaThe knowledge on the subject of magnetized transport have remained little changed in the field of cold plasmas since the 1960s and is no longer sufficient to explain the complex behavior of the plasma which is found in low-pressure magnetized sources currently under development. Theories and methods developed for the study of magnetized transport in the context of the thermonuclear fusion energy research are inadequate to describe the nonambipolar dynamics of these plasmas. Indeed, in these sources, ions are weakly magnetized, collisions with neutral significantly influence the transport whereas walls are perfect sinks for particles and control equilibrium profiles. To address this problematic, this thesis revisits the cold plasmas modelling and proposes a new model describing the magnetized fluid transport in the plane perpendicular to the magnetic field. We address the complexity of this transport through the development of a 2D+1/2 fluid model and its numerical scheme without approximation on the ordering between characteristic lengths scales of magnetized plasmas (i. E. The plasma size Lambda, the mean free path lai,e and Larmor radii of ions and electrons rho Li,e). The equations are solved in the plane perpendicular to the magnetic field where asymmetries and inhomogeneities representative of the magnetized transport appear, while the boundary conditions (parallel and transverse) are derived from the classical sheath theory. Moreover, the consideration of particles inertia makes the model able to capture the plasma transient dynamics and certain types of instabilities. The model, which supports a wide range of magnetic field strengths and topologies, is applied to the configurations of two negative ions sources. Asymmetries and inhomogeneities observed experimentally are recovered and, in a geometry representing the Scrape-Of-Layer of tokamaks, the model is able to simulate the interchange turbulence which is thought to dominate the perpendicular transport of the edge plasma
Abiteboul, Jérémie. "Transport turbulent et néoclassique de quantité de mouvement toroïdale dans les plasmas de tokamak". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4062/document.
Pełny tekst źródłaThe goal of magnetic confinement devices such as tokamaks is to produce energy from nuclear fusion reactions in plasmas at low densities and high temperatures. Experimentally, toroidal flows have been found to significantly improve the energy confinement, and therefore the performance of the machine. As extrinsic momentum sources will be limited in future fusion devices such as ITER, an understanding of the physics of toroidal momentum transport and the generation of intrinsic toroidal rotation in tokamaks would be an important step in order to predict the rotation profile in experiments. Among the mechanisms expected to contribute to the generation of toroidal rotation is the transport of momentum by electrostatic turbulence, which governs heat transport in tokamaks. Due to the low collisionality of the plasma, kinetic modeling is mandatory for the study of tokamak turbulence. In principle, this implies the modeling of a six-dimensional distribution function representing the density of particles in position and velocity phase-space, which can be reduced to five dimensions when considering only frequencies below the particle cyclotron frequency. This approximation, relevant for the study of turbulence in tokamaks, leads to the so-called gyrokinetic model and brings the computational cost of the model within the presently available numerical resources. In this work, we study the transport of toroidal momentum in tokamaks in the framework of the gyrokinetic model
RUFFIN, EMMANUEL. "Etude de jets turbulents a densite variable a l'aide de modeles de transport au second ordre". Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX22097.
Pełny tekst źródłaRos, i. Sala Àlex. "Effects of aquatic vegetation on sediment transport". Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/401629.
Pełny tekst źródłaAls marges dels continents hi ha les zones costaneres, regions d’altra productivitat biològica. Les zones costaneres inclouen, entre d’altres, els aiguamolls, que són zones terrestres inundades permanentment o estacionalment, caracteritzades per la presència de vegetació aquàtica adaptada a sols hídrics. És per tant necessari considerar l’efecte de les praderies aquàtiques en les investigacions en aiguamolls. Aquestes àrees estan governades per forces físiques originades per corrents de marees, ones, vent, conveccions nocturnes i inundacions. L’objectiu d’aquesta tesi és estudiar el transport de sediments en aiguamolls on el fluid és dominat per a) ones progressives, b) turbulència gairebé isòtropa i c) inundacions extremes
Lachaussée, Florent. "Érosion et transport de particules au voisinage d'un obstacle". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS377/document.
Pełny tekst źródłaErosion occurs when a fluid flowing over a granular bed exerts a large enough shear stress. When the fluid encounters an obstacle, the modification of the flow leads to a local over speed, and thus on an increase of the shear stress in the vicinity of the obstacle. As a result, the erosion is locally enhanced and is called scouring. In this work, we investigate this complicated situation experimentally at the laboratory scale. In particular, we address the question of the scouring threshold, i.e., the minimum critical approach velocity of the fluid leading to erosion in the vicinity of the obstacle. We report the existence of two different scouring patterns: the traditional horseshoe scour at the base of the obstacle, which dominates at large flow velocities, and we also highlight another scouring pattern downstream, which is called rabbit ear scour, at moderate speeds. We determine the onset of both erosion patterns visually using different grains and obstacles. Besides, we measure the bed topography over time using a laser profilometer. By monitoring the bed topography during the scouring process, we characterize the morphology of both scouring patterns and rationalize their competitive dynamics by measuring their formation timescale. In most cases, the rabbit ear scour development is inhibited by the faster horseshoe scour growth. The characterization of the flow using Particles Image Velocimetry (PIV), provides information on the shear stress exerted by the fluid flow on the grains, with and without obstacle. We can thus rationalize the threshold values for both scouring patterns, associated with different flow structures
Frey, Philippe. "Etude expérimentale et simulation numérique du transport turbulent de particules solides dans un décanteur". Ecully, Ecole centrale de Lyon, 1991. http://bibli.ec-lyon.fr/exl-doc/TH_T1412_pfrey.pdf.
Pełny tekst źródłaTransport of solid particles in suspension within a turbulent flow has been studied in physical models of settling tanks consisting of a sloping backward facing step and an outlet weir. Mean and fluctuating velocities have been measured by laser Doppler anemometry particularly in the recirculation region generated by the step. Particles injection allowed to determine percentages of outgoing particles as well as the repartition of sedimented particles. Thèse experimental results were used to assess the influence of the geometry on the settling tank efficiency. Experimental results on velocity fields were compared with a vertical two-dimensional turbulence model (VEST code). Results relative to the transport of particles were confronted to the output of an eulero-lagrangian three-dimensional model for the simulation of solid particles trajectories (TRAPS code). This code uses as input the mean field calculated by VEST. A good agreement has been obtained on outgoing percentages as well as on the repartition of sedimented particles
Hauët, Gwenaël. "Contrôle de la turbulence par simulation des grandes échelles en transport supersonique". Grenoble INPG, 2003. http://www.theses.fr/2003INPG0118.
Pełny tekst źródłaBarnes, Michael Alexander. "Trinity a unified treatment of turbulence, transport, and heating in magnetized plasmas /". College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9233.
Pełny tekst źródłaThesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Loisy, Aurore. "Direct numerical simulation of bubbly flows : coupling with scalar transport and turbulence". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1142/document.
Pełny tekst źródłaThis thesis is devoted to the study of homogeneous bubbly flows and their coupling with scalar transport and turbulence. It focuses on the effects of finite size, hydrodynamic interactions, and suspension microstructure, which are investigated using direct numerical simulations at the bubble scale. The dynamics of laminar buoyancy-driven bubbly suspensions is first revisited. More specifically, the effect of volume fraction on the bubble drift velocity is clarified by connecting numerical results to theory for dilute ordered systems, and similarities between perfectly ordered and free disordered suspensions are evidenced. These results are then used for the modeling of passive scalar transport in laminar suspensions as described by an effective diffusivity tensor, and crucial differences between ordered and disordered systems with respect to scalar transport are highlighted. Lastly, turbulence is included in the simulations, and its interaction with a finite-size bubble is characterized. The behavior of a bubble as large as Taylor microscale is shown to share a number of common features with that of a microbubble, most notably, the flow sampled by the bubble is biased. A definition of the liquid flow seen by the bubble, as it enters in usual models for the added mass and the lift forces, is finally proposed
Rea, Cristina. "3D physics, turbulence and transport in the plasma boundary of RFX-mod". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424023.
Pełny tekst źródłaIl crescente aumento nella richiesta di produzione energetica è diventato un costante leitmotif che caratterizza la società in cui viviamo. L'impossibilità di riuscire a soddisfare tali richieste sfruttando opzioni già esistenti che siano economicamente vantaggiose ed al contempo rispettino l’ambiente, è ormai una consapevolezza globalmente diffusa. La International Energy Agency ha esaustivamente documentato attraverso i suoi report annuali che le riserve di gas naturale e combustibile fossile si esauriranno nel giro di qualche decade a causa della sempre più crescente richiesta di energia. Come provvedere a soddisfare le esigenze energetiche di una popolazione mondiale in continuo aumento diventerà ben presto un problema critico. E' all'interno di questo quadro globale che entra in gioco la ricerca sulla fusione come risorsa energetica. Al fine di poter dimostrare la sfruttabilità della fusione nucleare quale risorsa energetica, la comunità scientifica internazionale ha da anni continuato ad investire nella ricerca sulla fusione termonucleare controllata. Ad oggi è nelle fasi finali di costruzione il più grande esperimento che coinvolga trasversalmente ricercatori da ogni parte del mondo. L'esperimento è denominato ITER (International Thermonuclear Experimental Reactor) e rappresenterà un banco di prova per la fisica della fusione e l’ingegneria. Tra le possibili configurazioni magnetiche adottabili sperimentalmente in una macchina da fusione, quella a campo magnetico rovesciato si è rivelata essere un eccellente strumento per studiare la fisica del plasma e le innumerevoli sfide scientifiche che essa pone. Tuttavia, per svariati motivi non è previsto l'utilizzo di tale configurazione in un reattore a fusione che produca energia a fini commerciali. L'esperimento RFX-mod ospitato presso il Consorzio RFX a Padova è il reversed-field pinch (RFP) più grande al mondo. L'attività di ricerca che verrà presentata in questo lavoro di tesi è stata svolta principalmente a Padova su RFX-mod ma ha anche previsto e contemplato la partecipazione ad una campagna sperimentale sul tokamak COMPASS a Praga. L’attività di ricerca che verrà presentata in questa tesi si concentra sulla caratterizzazione degli effetti 3D sui meccanismi di trasporto nella regione più esterna del plasma di RFX-mod. La macchina risulta essere estremamente versatile in quanto sono possibili operazioni in configurazione a campo rovesciato e in configurazione tokamak. Nello svolgimento della tesi verrà fornita una descrizione dettagliata delle proprietà di trasporto al bordo del plasma in entrambe le configurazioni magnetiche. L'approccio che verrà seguito può essere descritto in termini di un duplice percorso condiviso tra l'investigazione delle fluttuazioni elettrostatiche delle proprietà di trasporto effettuato attraverso l'utilizzo di sonde inseribili nel plasma e lo studio dei cambiamenti della topologia magnetica dovuti a meccanismi spontanei di tipo 3D. La tesi viene così organizzata: Parte I, Introduzione. Nella prima parte della tesi verranno introdotte tutte le nozioni di base utili allo svolgimento del lavoro. Nel capitolo 1 sarà discusso il concetto di plasma e fisica della fusione assieme ad una descrizione dettagliata delle due configurazioni magnetiche rilevanti ai fini delle analisi effettuate: la configurazione reversed-field pinch (RFP) e tokamak. Nel capitolo 2 la dinamica di un RFP verrà dettagliatamente descritta attraverso la teoria di Taylor. Inoltre verranno discussi gli stati a singola e multipla elicità (stati SH e MH), caratteristici della dinamica di un RFP. Successivamente verrà descritta la regione più esterna del plasma di RFX-mod, anche attraverso gli strumenti principali utilizzati nelle analisi effettuate. Il capitolo si concluderà quindi con l'introduzione di una analogia, che sarà dominante in tutto il corpo della tesi, tra la regione esterna di un plasma di tipo RFP e di uno di tipo tokamak durante esperimenti che prevedano l'applicazione di perturbazioni magnetiche. Parte II, Analisi di trasporto. Il capitolo 3 si apre con la presentazione delle due configurazioni sperimentali adottate per RFX-mod ai fini delle analisi di trasporto. Negli esperimenti è stata utilizzata la sonda inseribile U-probe, che verrà descritta successivamente assieme alla teoria su cui si basano le misure da essa raccolte. Verranno quindi discussi i risultati derivanti dall'investigazione delle fluttuazioni elettrostatiche nella regione di bordo del plasma. Verranno di seguito presentati gli studi sui meccanismi di trasporto in differenti regioni topologiche in presenza di una perturbazione magnetica esternamente applicata. Tali risultati verranno mostrati per esperimenti condotti su RFX-mod sia in configurazione reversed-field pinch che in configurazione tokamak. Parte III, Analisi topologiche. Lo studio dei cambiamenti della topologia magnetica si sviluppa attraverso l'analisi di eventi spontanei di riconnessione magnetica in configurazione a campo rovesciato. Nel capitolo 4 verranno inizialmente discussi alcuni modelli di riconnessione magnetica. Verranno quindi presentati i cosiddetti eventi di crash all'interno di RFX-mod e verrà dettagliatamente descritta la tecnica di analisi adottata. Nella seconda parte del capitolo verranno descritti gli esperimenti effettuati sul tokamak COMPASS e su RFX-mod sfruttando un'altra sonda inseribile che ha lo scopo di analizzare il profilo di temperatura ionica. Parte IV, Conclusioni. Nel capitolo 5 sono raccolti e discussi i risultati della tesi. Infine, viene fornita una sezione in cui i principali risultati sono trattati sinteticamente insieme ai problemi rimasti aperti in vista di future prospettive di ricerca. Parte V, Appendici. In Appendice A è possibile trovare una descrizione dettagliata del formalismo della Magnetoidrodinamica mentre in Appendice B vengono trattate in dettaglio le equazioni per il trasporto utili ai fini della tesi.