scholarly journals Gyrokinetic simulations for turbulent transport of multi-ion-species plasmas in helical systems

2020 ◽  
Vol 27 (5) ◽  
pp. 052501
Author(s):  
M. Nunami ◽  
M. Nakata ◽  
S. Toda ◽  
H. Sugama
Keyword(s):  
Turbulent Transport ◽  
Ion Species ◽  
Gyrokinetic Simulations

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

2013 ◽  
Vol 20 (12) ◽  
pp. 122312 ◽  
Author(s):  
D. Told ◽  
F. Jenko ◽  
T. Görler ◽  
F. J. Casson ◽  
E. Fable ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Gyrokinetic Simulations

Gyrokinetic Simulations of Turbulent Transport in a Ring Dipole Plasma

2009 ◽  
Vol 103 (5) ◽  
Author(s):  
Sumire Kobayashi ◽  
Barrett N. Rogers ◽  
William Dorland
Keyword(s):  
Turbulent Transport ◽  
Gyrokinetic Simulations

scholarly journals How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Ajay C. J. ◽  
Stephan Brunner ◽  
Ben McMillan ◽  
Justin Ball ◽  
Julien Dominski ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Zonal Flow ◽  
System Size ◽  
Flow Shear ◽  
Direction Parallel ◽  
Zonal Flows ◽  
Radial Extent ◽  
Modulational Instabilities ◽  
Gyrokinetic Simulations ◽  
The Magnetic Field

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for kinetic passing electron dynamics and is known to generate stationary $E\times B$ zonal flow shear layers at radial locations near low-order mode rational surfaces (Weikl et al. Phys. Plasmas, vol. 25, 2018, 072305). We find that self-interaction, in fact, plays a very significant role in also generating fluctuating zonal flows, which is critical to regulating turbulent transport throughout the radial extent. Unlike the usual picture of zonal flow drive in which microinstability eigenmodes coherently amplify the flow via modulational instabilities, the self-interaction drive of zonal flows from these eigenmodes are uncorrelated with each other. It is shown that the associated shearing rate of the fluctuating zonal flows therefore reduces as more toroidal modes are resolved in the simulation. In simulations accounting for the full toroidal domain, such an increase in the density of toroidal modes corresponds to an increase in the toroidal system size, leading to a finite system size effect that is distinct from the well-known profile shearing effect.

Gyrokinetic simulations of turbulent transport: size scaling and chaotic behaviour

2010 ◽  
Vol 52 (12) ◽  
pp. 124038 ◽  
Author(s):  
L Villard ◽  
A Bottino ◽  
S Brunner ◽  
A Casati ◽  
J Chowdhury ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Chaotic Behaviour ◽  
Size Scaling ◽  
Gyrokinetic Simulations

Continuous-in-time approach to flow shear in a linearly implicit local gyrokinetic code

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Nicolas Christen ◽  
Michael Barnes ◽  
Felix I. Parra
Keyword(s):  
Turbulent Transport ◽  
Current Approach ◽  
Test Cases ◽  
Time Step ◽  
Flow Shear ◽  
New Approach ◽  
Step Flow ◽  
Discrete Approach ◽  
Stringent Constraint ◽  
Gyrokinetic Simulations

A new algorithm for toroidal flow shear in a linearly implicit, local $\delta f$ gyrokinetic code is described. Unlike the current approach followed by a number of codes, it treats flow shear continuously in time. In the linear gyrokinetic equation, time-dependences arising from the presence of flow shear are decomposed in such a way that they can be treated explicitly in time with no stringent constraint on the time step. Flow shear related time dependences in the nonlinear term are taken into account exactly, and time dependences in the quasineutrality equation are interpolated. Test cases validating the continuous-in-time implementation in the code GS2 are presented. Lastly, nonlinear gyrokinetic simulations of a JET discharge illustrate the differences observed in turbulent transport compared with the usual, discrete-in-time approach. The continuous-in-time approach is shown, in some cases, to produce fluxes that converge to a different value than with the discrete approach. The new approach can also lead to substantial computational savings by requiring radially narrower boxes. At fixed box size, the continuous implementation is only modestly slower than the previous, discrete approach.

scholarly journals Validation of nonlinear gyrokinetic transport models using turbulence measurements

2019 ◽  
Vol 85 (1) ◽  
Author(s):  
A. E. White
Keyword(s):  
Model Validation ◽  
Transport Model ◽  
Turbulent Transport ◽  
Fusion Plasmas ◽  
Transport Models ◽  
Turbulence Measurements ◽  
Diagnostic Models ◽  
History Of ◽  
Gyrokinetic Simulations

This tutorial covers validation of gyrokinetic turbulent-transport models via comparison of measured turbulence with realistic simulations of fusion plasmas. It presents a brief history of validation of gyrokinetic simulations, the principal challenges encountered, a limited survey of common turbulence diagnostics used on tokamaks and stellarators, an overview of the fundamentals of synthetic diagnostic models and a discussion of frontiers in turbulent-transport model validation.

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