用神经网络建模电子压力,提升磁鞘湍流模拟精度。
Electron neural closure for turbulent magnetosheath simulations: energy channels
- 用全卷积神经网络学习非局部电子压力闭合关系。
- 在少粒子模拟中训练,成功推广到多粒子场景且保持统计特性。
- 显著优于传统局部闭合方法,适合高精度等离子体模拟研究者。
本文提出一种基于全卷积神经网络(FCNN)的非局部五矩电子压力张量闭合模型,用于改进磁鞘湍流的全动能守恒半隐式粒子-网格模拟。该模型通过少量粒子/单元的代表性模拟数据进行训练,验证了其在大量粒子/单元情形下的泛化能力。重点评估了所学状态方程的压力-应变相互作用统计特性,这对理解湍流能量通道至关重要。结果表明,神经网络学习的方程在整体压力-应变空间分布及其条件平均上重建良好;尽管小尺度特征(尤其是压力张量非对角分量)仍存在缺失,但增加训练数据可显著改善性能,显示出良好扩展性与优化潜力,后续工作将重点解决此问题。
原文摘要 · Abstract (English)
In this work, we introduce a non-local five-moment electron pressure tensor closure parametrized by a Fully Convolutional Neural Network (FCNN). Electron pressure plays an important role in generalized Ohm's law, competing with electron inertia. This model is used in the development of a surrogate model for a fully kinetic energy-conserving semi-implicit Particle-in-Cell simulation of decaying magnetosheath turbulence. We achieve this by training FCNN on a representative set of simulations with a smaller number of particles per cell and showing that our results generalise to a simulation with a large number of particles per cell. We evaluate the statistical properties of the learned equation of state, with a focus on pressure-strain interaction, which is crucial for understanding energy channels in turbulent plasmas. The resulting equation of state learned via FCNN significantly outperforms local closures, such as those learned by Multi-Layer Perceptron (MLP) or double adiabatic expressions. We report that the overall spatial distribution of pressure-strain and its conditional averages are reconstructed well. However, some small-scale features are missed, especially for the off-diagonal components of the pressure tensor. Nevertheless, the results are substantially improved with more training data, indicating favorable scaling and potential for improvement, which will be addressed in future work.
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