Physics basis of Multi-Mode anomalous transport module

Rafiq, T.; Kritz, A.H.; Weiland, Jan; Pankin, A.Y.; Luo, Lixiang

doi:10.1063/1.4794288

Cited by 62 publications

(49 citation statements)

References 44 publications

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“…(13). We have then used the Waltz rule [37][38][39] to obtain the stabilization of the drift waves caused by the flow shear (13). The resonance of the potential u at the fluid resonance is the same as obtained in transport simulations giving the L-H transition on EAST 35 and the nonlinear Dimits upshift.…”

Section: Discussionmentioning

confidence: 99%

On the normalization of transport from ITG Modes

Weiland

Zagorodny

2016

Physics of Plasmas

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We have analyzed the interplay of ITG turbulence and zonal flows as derived by the reductive perturbation method. Not surprisingly, the overall transport level depends strongly on the physics description of ITG modes. In particular, the fluid resonance turns out to play a dominant role for the excitation of zonal flows. This is the mechanism recently found to lead to the L-H transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have here taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers, and Dimits shift. Published by AIP Publishing.

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Section: Discussionmentioning

confidence: 99%

On the normalization of transport from ITG Modes

Weiland

Zagorodny

2016

Physics of Plasmas

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“…It is then convolved with a second model for the fluctuation spectral intensity hjṽ r;k j 2 i which may come from calibration of the model against experimental data, 69 analytic theory arguments, 36,70,71 or fits to databases of nonlinear simulations. 46,72,73 The underlying physical motivation for this approach is that unlike many neutral fluid turbulence systems, in the core region of MFE-relevant core plasmas, the fluctuations saturate at small amplitude and retain many of the linear wave characteristics of the underlying instabilities.…”

Section: Basics Of Turbulence and Transport Modeling In Magneticmentioning

confidence: 99%

Validation metrics for turbulent plasma transport

Holland

2016

Physics of Plasmas

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Developing accurate models of plasma dynamics is essential for confident predictive modeling of current and future fusion devices. In modern computer science and engineering, formal verification and validation processes are used to assess model accuracy and establish confidence in the predictive capabilities of a given model. This paper provides an overview of the key guiding principles and best practices for the development of validation metrics, illustrated using examples from investigations of turbulent transport in magnetically confined plasmas. Particular emphasis is given to the importance of uncertainty quantification and its inclusion within the metrics, and the need for utilizing synthetic diagnostics to enable quantitatively meaningful comparisons between simulation and experiment. As a starting point, the structure of commonly used global transport model metrics and their limitations is reviewed. An alternate approach is then presented, which focuses upon comparisons of predicted local fluxes, fluctuations, and equilibrium gradients against observation. The utility of metrics based upon these comparisons is demonstrated by applying them to gyrokinetic predictions of turbulent transport in a variety of discharges performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], as part of a multi-year transport model validation activity.

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“…13 In order to understand how MTMs affect transport and consequently the evolution of electron temperature in tokamak discharges, a reduced transport model for microtearing modes is needed for use in integrated predictive modeling. 15 The derivation of the MTM model requires the development of a nonlinear dispersion relation for MTMs. In this paper, the derivation of the dispersion relations begins with an approach that utilizes the linear gyrokinetic equation for electrons in which there is no constraint on the magnitude of the collision frequency relative to the mode frequency.…”

Section: Introductionmentioning

confidence: 99%

Microtearing modes in tokamak discharges

et al. 2016

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Microtearing modes (MTMs) have been identified as a source of significant electron thermal transport in tokamak discharges. In order to describe the evolution of these discharges, it is necessary to improve the prediction of electron thermal transport. This can be accomplished by utilizing a model for transport driven by MTMs in whole device predictive modeling codes. The objective of this paper is to develop the dispersion relation that governs the MTM driven transport. A unified fluid/kinetic approach is used in the development of a nonlinear dispersion relation for MTMs. The derivation includes the effects of electrostatic and magnetic fluctuations, arbitrary electron-ion collisionality, electron temperature and density gradients, magnetic curvature, and the effects associated with the parallel propagation vector. An iterative nonlinear approach is used to calculate the distribution function employed in obtaining the nonlinear parallel current and the nonlinear dispersion relation. The third order nonlinear effects in magnetic fluctuations are included, and the influence of third order effects on a multi-wave system is considered. An envelope equation for the nonlinear microtearing modes in the collision dominant limit is introduced in order to obtain the saturation level. In the limit that the mode amplitude does not vary along the field line, slab geometry, and strong collisionality, the fluid dispersion relation for nonlinear microtearing modes is found to agree with the kinetic dispersion relation. Published by AIP Publishing.

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Physics basis of Multi-Mode anomalous transport module

Cited by 62 publications

References 44 publications

On the normalization of transport from ITG Modes

On the normalization of transport from ITG Modes

Validation metrics for turbulent plasma transport

Microtearing modes in tokamak discharges

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