Article
Computer Science, Interdisciplinary Applications
PengFei Zhao, Lei Ye, Nong Xiang
Summary: A new method based on time diffusion technique is developed to mitigate numerical instability caused by high frequency electrostatic shear Alfven wave in gyrokinetic simulation of electrostatic turbulence. It fully preserves drift-kinetic electron effects and can be efficiently incorporated with explicit time integration scheme, successfully applied to linear and nonlinear ITG/TEM turbulence simulations, improving numerical stability and enlarging time step size in electrostatic turbulence simulation in tokamaks.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Physics, Fluids & Plasmas
Tajinder Singh, Javier H. Nicolau, Zhihong Lin, Sarveshwar Sharma, Abhijit Sen, Animesh Kuley
Summary: In this study, global gyrokinetic simulations are conducted to investigate the ion temperature gradient (ITG) and trapped electron mode (TEM) in the LHD stellarator. The simulations reveal that kinetic electron effects significantly enhance the growth rate and turbulent transport levels. Zonal flow is found to dominate the saturation mechanism in ITG turbulence, while the inverse cascade of toroidal harmonics plays a crucial role in the saturation of TEM turbulence. Furthermore, the simulations indicate that ITG turbulence is more effective in driving heat conductivity, while TEM turbulence is more efficient for particle diffusivity.
Article
Physics, Fluids & Plasmas
Javier H. Nicolau, Gyungjin Choi, Jingyuan Fu, Pengfei Liu, Xishuo Wei, Zhihong Lin
Summary: The helical components of the equilibrium magnetic field have significant impacts on zonal flow, while kinetic electrons can reduce zonal flow residue and increase the frequency of low frequency oscillation. Additionally, linear toroidal coupling of multiple toroidal n-harmonics barely affects zonal flows but can generate long wavelength toroidal harmonics with the same toroidal number as the helical magnetic field.
Article
Physics, Fluids & Plasmas
T. N. Bernard, F. D. Halpern, M. Francisquez, N. R. Mandell, J. Juno, G. W. Hammett, A. Hakim, G. J. Wilkie, J. Guterl
Summary: This study presents the novel coupling of a continuum full-F gyrokinetic turbulence model with a 6D continuum model for kinetic neutrals using the Gkeyll code. The aim is to improve the understanding of the role of neutrals in plasma fueling, detachment, and their interaction with edge plasma profiles and turbulence statistics.
PHYSICS OF PLASMAS
(2022)
Article
Computer Science, Interdisciplinary Applications
Kenji Nishioka, Tomo-Hiko Watanabe, Shinya Maeyama
Summary: This study introduces a novel time integration method for drift kinetic equations, where low order fluid moment equations are extracted to allow for implicit solver for wave propagation and explicit solver for kinetic part. Numerical tests have shown that the new scheme enables stable and accurate time integration, with the ability to take larger time step sizes when electron beta value is smaller than electron-to-ion mass ratio.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
Baoyi Xie, Lei Ye, Yang Chen, Pengfei Zhao, Yang Ye, Xin Lin, Heng Lan, Wenfeng Guo, Nong Xiang
Summary: Linear and nonlinear simulations have been conducted for the edge coherent mode (ECM) using the global gyrokinetic code GEM based on experimental parameters from the EAST tokamak. The simulations have shown that ECM is an electrostatic mode with dominant toroidal mode number n=18 and frequency around 48 kHz, propagating along the direction of electron diamagnetic drift, consistent with experimental observations. The nonlinear simulations have further revealed that ECM induces saturated particle and heat fluxes primarily through perturbed electrostatic ExB drift, with roughly equal fluxes of electrons and ions. ECM drives outward particle and heat fluxes, facilitating the maintenance of long pulse H-mode by promoting turbulence.
Article
Computer Science, Interdisciplinary Applications
R. Kleiber, M. Borchardt, R. Hatzky, A. Koenies, H. Leyh, A. Mishchenko, J. Riemann, C. Slaby, J. M. Garcia-Regana, E. Sanchez, M. Cole
Summary: This paper describes the current state of the EUTERPE code, focusing on the implemented models and their numerical implementation. The code is capable of solving the multi-species electromagnetic gyrokinetic equations in a three-dimensional domain. It utilizes noise reduction techniques and grid resolution transformation for efficient computation. Additionally, various hybrid models are implemented for comparison and the study of plasma-particle interactions. The code is parallelized for high scalability on multiple CPUs.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Wai Hong Ronald Chan, Iain D. Boyd
Summary: Direct kinetic solvers allow for accurate simulation of multiscale plasmas in various applications, but they require a detailed understanding of grid-point requirements to ensure efficient mesh design and high predictivity.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Qingjiang Pan, Darin R. Ernst, David R. Hatch
Summary: This study goes beyond previous models by using an accurate gyrokinetic Fokker-Planck collision operator to demonstrate important corrections in simulating turbulence in magnetically confined fusion plasmas, showing significant improvements in predicting particle and energy loss while reducing computational demands.
Article
Computer Science, Interdisciplinary Applications
Emily Bourne, Yann Munschy, Virginie Grandgirard, Michel Mehrenberger, Philippe Ghendrih
Summary: Numerical methods based on non-uniform splines of varying degrees are used to simulate the plasma sheath in this study. A new well-conditioned method and the construction of a simulation grid from non-uniform knots are proposed to improve precision and reduce memory requirements. The non-uniform simulations using GPU parallelization achieve a 5.5 times speedup compared to uniform simulations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Tajinder Singh, Deepti Sharma, Tanmay Macwan, Sarveshwar Sharma, Joydeep Ghosh, Abhijit Sen, Zhihong Lin, Animesh Kuley
Summary: Global gyrokinetic simulations are conducted to study the electrostatic microturbulence driven by pressure gradients of thermal ions and electrons in the ADITYA-U tokamak geometry. Collisional effects are taken into account. The dominant instability is identified as trapped electron mode (TEM) based on its linear eigenmode structure and propagation in the electron diamagnetic direction. Turbulence and transport are suppressed to some extent by collisional effects. Zonal flow does not play a critical role in TEM saturation, with the inverse cascade dominating. The frequency spectrum of electrostatic fluctuations is in broad agreement with experimentally recorded spectrum in ADITYA-U, ranging from approximately 0 to 50 kHz.
Article
Computer Science, Interdisciplinary Applications
Usman Riaz, E. Seegyoung Seol, Robert Hager, Mark S. Shephard
Summary: The accurate representation and effective discretization of a problem domain into a mesh are crucial for achieving high-quality simulation results and computational efficiency. This work presents recent developments in extending an automated tokamak modeling and meshing infrastructure to better support the near flux field following meshing requirements of the XGC Gyro-kinetic Code.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Physics, Multidisciplinary
Aristeides D. Papadopoulos, Johan Anderson, Eun-jin Kim, Michail Mavridis, Heinz Isliker
Summary: A geometrical method for assessing stochastic processes in plasma turbulence is investigated, using a Riemannian metric on the phase space to compute distances between thermodynamic states. This method provides a geometric approach to understand stochastic processes, such as order-disorder transitions. The study focuses on gyrokinetic simulations of ion-temperature-gradient (ITG)-mode-driven turbulence in the W7-X stellarator.
Article
Physics, Multidisciplinary
Juliane U. Klamser, Olivier Dauchot, Julien Tailleur
Summary: The study reveals that for kinetic Monte Carlo descriptions of active particles, a continuous-time limit is ill-defined when relying solely on persistent, active steps. However, mixing passive steps with active ones can lead to a well-defined continuous-time limit. New KMC algorithms are proposed to obtain dynamics of active Ornstein-Uhlenbeck, active Brownian, and run-and-tumble particles.
PHYSICAL REVIEW LETTERS
(2021)
Article
Computer Science, Interdisciplinary Applications
Gahyung Jo, Jae-Min Kwon, Janghoon Seo, Eisung Yoon
Summary: A hyperbolic solver is developed for the gyrokinetic equation in tokamak geometry. The effects of basis functions on the numerical solutions and the conservation of physical quantities are investigated. The weighted basis functions show better performance in resolving small scale structures in velocity space.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Nuclear Science & Technology
G. M. Wallace, C. E. Kessel, J. Hosea, R. Majeski, J. R. Wilson, T. Rognlien, L. M. Waganer
FUSION SCIENCE AND TECHNOLOGY
(2020)
Article
Physics, Fluids & Plasmas
A. E. Jaervinen, S. L. Allen, A. W. Leonard, A. G. McLean, A. L. Moser, T. D. Rognlien, C. M. Samuell
CONTRIBUTIONS TO PLASMA PHYSICS
(2020)
Article
Physics, Fluids & Plasmas
A. Holm, D. Rognlien, W. H. Meyer
CONTRIBUTIONS TO PLASMA PHYSICS
(2020)
Article
Physics, Fluids & Plasmas
A. E. Jaervinen, S. L. Allen, D. Eldon, M. E. Fenstermacher, M. Groth, D. N. Hill, C. J. Lasnier, A. W. Leonard, A. G. McLean, A. L. Moser, G. D. Porter, T. D. Rognlien, C. M. Samuell, H. Q. Wang, J. G. Watkins
Article
Nuclear Science & Technology
Sungjin Kwon, Kihak Im, Suk-Ho Hong, Hyungho Lee, Thomas D. Rognlien, William Meyer, Keeman Kim
FUSION ENGINEERING AND DESIGN
(2020)
Article
Nuclear Science & Technology
David Humphreys, A. Kupresanin, M. D. Boyer, J. Canik, C. S. Chang, E. C. Cyr, R. Granetz, J. Hittinger, E. Kolemen, E. Lawrence, V. Pascucci, A. Patra, D. Schissel
JOURNAL OF FUSION ENERGY
(2020)
Article
Physics, Fluids & Plasmas
L. Ricketson, A. Hakim, J. Hittinger
Summary: Two coupling schemes for gyrokinetic simulations of microturbulence in tokamaks are proposed: one based on additive Schwarz domain decomposition and the other relying on the addition of source terms. Testing shows that these schemes have demonstrated good performance in accelerating computation and ensuring consistency and stability.
PHYSICS OF PLASMAS
(2021)
Article
Nuclear Science & Technology
A. Khrabry, V. A. Soukhanovskii, T. D. Rognlien, M. Umansky, D. Moulton, J. R. Harrison
Summary: The study used UEDGE modeling to investigate the complex relationship between SF and SN divertors, showing that SF divertors approach detachment conditions at lower upstream density compared to SN divertors, and have broader heat flux profiles with reduced peak values.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Nuclear Science & Technology
M. Zhao, A. E. Jaervinen, I Joseph, T. D. Rognlien
Summary: A model of ion temperature anisotropy for 2D plasma transport in the scrape-off layer of tokamaks is described and implemented in the UEDGE fluid transport code. Simulations demonstrate that ion parallel flows near the magnetic X-point can be overestimated by the standard isotropic Braginskii model in low collisionality regime. The 2D ion temperature anisotropy varies substantially near the X-point and near the divertor target plates, affecting the transport of ions across the scrape-off layer.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Nuclear Science & Technology
A. Holm, P. Boerner, T. D. Rognlien, W. H. Meyer, M. Groth
Summary: Comparing a fluid collisional-radiative model for H-2 implemented in UEDGE with the kinetic neutral code EIRENE, it was found that the agreement between the two models is within 20% under certain conditions. Additionally, when wall recycling was taken into account, EIRENE predicted molecular densities up to 2.2 times higher than UEDGE, possibly due to differences in physical processes between the two models.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Physics, Fluids & Plasmas
A. Khrabry, V. A. Soukhanovskii, T. D. Rognlien, M. Umansky, D. Moulton, J. R. Harrison
Summary: This study simulated the effects of magnetic configurations of snowflake (SF) divertor and standard divertor on plasma transport and heat flux using the two-dimensional multi-fluid code UEDGE. The results showed that the SF divertor has wider heat flux profiles and achieves outer and inner strike point detachment at lower upstream density compared to the standard divertor.
Article
Physics, Fluids & Plasmas
Menglong Zhao, Tom Rognlien, Aaro Jarvinen, Ilon Joseph
Summary: Understanding tokamak exhaust-power heat loads on divertor plates depends critically on having a realistic model of the scrape-off layer (SOL) plasma. Implementing ion temperature anisotropy effects allows for a detailed study of its impact on plasma transport, showing significant effects on plasma parallel transport near the magnetic X-point. The extra mirror force introduced by ion temperature anisotropy may be one of the main forces contributing to plasma flow in the SOL.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Mathematics, Applied
Alyson Fox, James Diffenderfer, Jeffrey Hittinger, Geoffrey Sanders, Peter Lindstrom
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2020)
Article
Mathematics, Applied
James Diffenderfer, Alyson L. Fox, Jeffrey A. Hittinger, Geoffrey Sanders, Peter G. Lindstrom
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2019)
Article
Nuclear Science & Technology
E. D. Emdee, R. J. Goldston, J. A. Schwartz, M. E. Rensink, T. D. Rognlien
NUCLEAR MATERIALS AND ENERGY
(2019)
