Applicability of different geometry approaches to simulations of turbulence in highly sheared magnetic fields

Told, D.; Jenko, F.

doi:10.1063/1.3365549

Cited by 6 publications

(19 citation statements)

References 27 publications

(31 reference statements)

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“…The first approach, the 'flux tube train' (Watanabe et al 2015), has been implemented in the local gyrokinetic codes GKV (Watanabe & Sugama 2006) and stella (Barnes, Parra & Landreman 2019). The other approach, the 'shifted metric' coordinate system (Scott 2001), has not been implemented in any local gyrokinetic code and it is currently unclear if it is possible to implement in a radially periodic domain (Told & Jenko 2010).…”

Section: Resolution Studymentioning

confidence: 99%

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

2020

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In this work, we highlight an issue that may reduce the accuracy of many local nonlinear gyrokinetic simulations -turbulent self-interaction through the parallel boundary condition. Given a sufficiently long parallel correlation length, individual turbulent eddies can span the full domain and "bite their own tails," thereby altering their statistical properties. Such self-interaction is only modeled accurately when the simulation domain corresponds to a full flux surface, otherwise it is artificially strong. For Cyclone Base Case parameters and typical domain sizes, we find that this mechanism modifies the heat flux by roughly 40% and it can be even more important. The effect is largest when using kinetic electrons, low magnetic shear, and strong turbulence drive (i.e. steep background gradients). It is found that parallel selfinteraction can be eliminated by increasing the parallel length and/or the binormal width of the simulation domain until convergence is achieved.

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Section: Resolution Studymentioning

confidence: 99%

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

2020

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“…The effects of different tokamak geometries on drift wave turbulence have been studied in both fluid 42,43 and gyrokinetic descriptions. 44,45…”

Section: Simulationsmentioning

confidence: 99%

Impurity transport in temperature gradient driven turbulence

Skyman¹,

Nordman²,

Strand³

2012

Physics of Plasmas

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In the present paper the transport of impurities driven by trapped electron (TE) mode turbulence is studied. Non-linear (NL) gyrokinetic simulations using the code GENE are compared with results from quasilinear (QL) gyrokinetic simulations and a computationally efficient fluid model. The main focus is on model comparisons for electron temperature gra- dient driven turbulence regarding the sign of the convective impurity velocity (pinch) and the impurity density gradient R/LnZ (peaking factor) for zero impurity flux. In particular, the scaling of the impurity peaking factors with impurity charge Z and with driving temper- ature gradient is investigated and compared with the results for Ion Temperature Gradient (ITG) driven turbulence. In addition, the impurity peaking is compared to the main ion peaking obtained by a self-consistent fluid calculation of the density gradients corresponding to zero particle fluxes. For the scaling of the peaking factor with impurity charge Z, a weak dependence is obtained from NL GENE and fluid simulations. The QL GENE results show a stronger dependence for low Z impurities and overestimates the peaking factor by up to a factor of two in this region. As in the case of ITG dominated turbulence, the peaking factors saturate as Z increases, at a level much below neoclassical predictions. However, the scaling with Z is weak or reversed as compared to the ITG case. The scaling of impurity peaking with the background temperature gradients is found to be weak in the NL GENE and fluid simulations. The QL results are also here found to significantly overestimate the peaking factor for low Z values. For the parameters considered, the background density gradient for zero particle flux is found to be slightly larger than the corresponding impurity zero flux gradient.Comment: 23 pages, 13 figures. Submitted to AIP: Physics of Plasma

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“…The convergence of the results at the chosen resolution was compared against a number of simulations using the shifted-metric approach. 28,29 The minimum finite toroidal mode number retained in the simulations was usually 2−8, with convergence checks done to ensure the sufficiency of this choice. Radial box sizes were usually chosen to be approximately 110ρ s (in GENE coordinates, see Sec.…”

Section: Methodology a Description Of Gyrokinetic Simulation Methodsmentioning

confidence: 99%

Characterizing turbulent transport in ASDEX Upgrade L-mode plasmas via nonlinear gyrokinetic simulations

et al. 2013

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The nature and level of turbulent transport in the outer core of low-confinement (L-mode) discharges performed at the ASDEX Upgrade tokamak [A. Kallenbach et al., Nucl. Fusion 51, 094012 (2011)] are examined. Previously, it was found that for an L-mode discharge of the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] gyrokinetic simulations were unable to reproduce the experimental ion heat flux, underestimating it by almost an order of magnitude. In the present work, employing the GENE gyrokinetic turbulence code, an extensive nonlinear study is performed for L-mode discharges of ASDEX Upgrade in order to cross-check this observation. It is shown that no systematic underprediction can be found in these simulations-instead, discrepancies with respect to experimental transport levels are small enough to be resolved within the uncertainties of the experimental profiles. Moreover, it is shown that some turbulence properties resemble closely those of the underlying linear microinstabilities at least out to 90% of the minor radius, so that quasilinear transport models remain in principle applicable even for these parameters, provided that appropriate nonlinear saturation rules can be developed.

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Applicability of different geometry approaches to simulations of turbulence in highly sheared magnetic fields

Cited by 6 publications

References 27 publications

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

Impurity transport in temperature gradient driven turbulence

Characterizing turbulent transport in ASDEX Upgrade L-mode plasmas via nonlinear gyrokinetic simulations

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