陀螺动力学$δf$代码stella的数值与诊断扩展
Numerical and diagnostic extensions to the gyrokinetic $δf$ code stella
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中文总结 AI 辅助
本研究在stella代码中扩展自由能诊断，应用于W7-X配置，揭示湍流级联幂律行为、数值不稳定性及实空间结构，并系统比较时间积分方案，指出SSP22和SSP33分别适用于线性和非线性模拟，为方案选择提供指导。
中文摘要 AI 辅助
理解磁化等离子体中的湍流需要能够捕捉跨尺度复杂自由能传递过程的稳健数值工具。我们展示了在stella代码的陀螺动力学模拟中，自由能作为物理湍流特性和数值稳定性诊断的效用。应用于W7-X高镜率配置时，自由能诊断揭示了湍流级联中的特征幂律行为，作为常规诊断无法检测到的数值不稳定性的敏感指标，并暴露了仅凭静电势无法显现的实空间局域结构。为支持这些分析，我们对显式时间积分方案进行了系统比较，表明最优选择关键取决于状态：SSP22在线性ITG模拟中实现最低计算成本，而SSP33在非线性饱和态中效率最高，非线性模拟所需的计算成本比线性情况高出两到三个数量级。这些结果确立了自由能诊断作为解释等离子体湍流的宝贵工具，并为stella模拟中的方案选择提供了实用指导。
英文摘要
Understanding turbulence in magnetised plasmas requires robust numerical tools capable of capturing complex free-energy transfer processes across scales. We demonstrate the utility of free energy as a diagnostic for both physical turbulence characteristics and numerical stability in gyrokinetic simulations with the stella code. Applied to the W7-X high-mirror configuration, free-energy diagnostics reveal characteristic power-law behaviour in the turbulent cascade, act as sensitive indicators of numerical instabilities undetected by conventional diagnostics, and expose localised structures in real space not apparent in the electrostatic potential alone. To support these analyses, we present a systematic comparison of explicit time-integration schemes, showing that the optimal choice depends critically on the regime: SSP22 achieves the lowest computational cost in linear ITG simulations, while SSP33 is most efficient in the nonlinear saturated state, with nonlinear simulations requiring two to three orders of magnitude more computational cost than linear cases. These results establish free-energy diagnostics as a valuable tool for interpreting plasma turbulence and provide practical guidance for scheme selection in stella simulations.
发表机构
- Institute of Physics, University of Greifswald（格赖夫斯瓦尔德大学物理研究所）
- Max Planck Institute for Plasma Physics（马克斯·普朗克等离子体物理研究所）
- Rudolf Peierls Centre, University of Oxford（牛津大学鲁道夫·派尔斯中心）
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