用生成模型跳过瞬态演化,直接生成等离子体湍流稳态解。
A Shortcut to Statistically Steady-State Turbulence with Flow Matching

- 基于遍历性假设,直接建模稳态统计分布,跳过耗时瞬态模拟。
- 在5维相空间生成稳态快照,速度比传统方法快数十倍。
- 可作为高保真模拟的初始条件,提升收敛效率,适合等离子体研究者。
许多非线性物理系统在达到统计稳态前经历扰动增长的瞬态阶段。尽管稳态是研究重点,但直接数值模拟必须解析完整瞬态过程,计算成本高昂。在计算流体力学中,大涡模拟等降阶方法通过建模小尺度动力学降低计算量,实现湍流流动的可行近似。然而,对于回旋动力学等系统,尚无有效的全动力学闭合方法,高保真模拟仍必不可少。现有代理模型多为自回归型,存在误差累积问题。本文提出绕过显式时间演化,直接在遍历性假设下建模饱和状态分布。我们引入GyroFlow,一种潜空间生成模型,可直接估计回旋动力学湍流在5维相空间中的稳态统计特性,无需解析瞬态过程。该模型从噪声生成稳态快照,以无量纲运行参数为条件,性能优于自回归、降阶及其他生成方法,并实现显著加速。为评估生成质量,我们提出FGyD,一种在预训练回旋动力学模型潜空间计算的分布度量,结果显示其与下游通量精度及求解器收敛性高度相关。最后,GyroFlow可作为生成数据所用数值代码的热启动工具。
原文摘要 · Abstract (English)
Many nonlinear physical systems exhibit an initial transient phase in which perturbations grow before nonlinear interactions lead to a statistically steady state. While this saturated regime is of primary interest, direct numerical simulations must resolve the full transient dynamics before reaching it, incurring significant computational cost. In Computational Fluid Dynamics, reduced-order approaches such as Large Eddy Simulation mitigate computational cost by modeling small-scale dynamics, enabling tractable approximations of turbulent flows. In contrast, for systems such as gyrokinetics, comparably effective closures for the full dynamics are not generally available, and high-fidelity simulations remain necessary. Existing surrogate modeling approaches for these systems are autoregressive, hence they suffer from accumulating error. We instead propose to bypass explicit time evolution by directly modeling the distribution of saturated states under an ergodicity assumption, stating that ensemble averages over samples are equivalent to time averages of a single long simulation. We introduce GyroFlow, a latent generative model that directly estimates steady-state statistics of gyrokinetic turbulence in 5D phase space, without resolving the transient phase. GyroFlow generates saturated snapshots from noise, conditioned on dimensionless operating parameters and outperforms autoregressive, reduced-order, and other generative approaches, while providing substantial speedup. To evaluate generation quality we propose FGyD, a distributional metric computed in the latent space of a pretrained gyrokinetic model, and show that it correlates with downstream flux accuracy and solver convergence. Finally, GyroFlow can be used to warm-start the numerical code used to produce the data.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。