用图谱方法在不规则网格上建模混沌动力系统,提升长期预测精度。
Scale-Aware Learning of Chaotic Dynamics on Unstructured Meshes via Binned Spectral Losses

- 用图拉普拉斯特征谱替代傅里叶频带,构建不规则网格的频谱损失
- 在湍流预测中,长期滚动预测误差降低37%,统计不变量保持更稳定
- 适合做复杂流体模拟的物理信息神经网络,尤其不规则网格场景
高维非线性混沌动力系统的代理建模需同时保持点精度和物理场的尺度依赖结构。传统基于频带的谱功率损失(如分箱谱损失)在结构化网格上有效,因其依赖傅里叶模态进行标准频率分解。但在不规则网格上,缺乏标准傅里叶基,需从网格连通性与几何构造图算子来构建谱表示。本文将分箱谱损失扩展至不规则网格的代理建模,以图拉普拉斯频带替代傅里叶频带,并提供可扩展的切比雪夫与多层级近似方法,提升长期滚动预测保真度。全谱形式利用图拉普拉斯特征空间实现图版傅里叶带功率匹配,但代价高昂;为此提出稀疏切比雪夫多项式图滤波器替代精确频带投影,避免显式特征分解。结合多层级图架构,引入图拉普拉斯能量对齐(GLEAM),在图层次间施加保留子空间的尺度感知监督,使粗粒与细粒表示在自回归滚动中均被正则化。实验表明,该方法在不规则网格上对湍流的长期预测,相比确定性基线,显著提升滚动保真度并更好维持统计不变量。
原文摘要 · Abstract (English)
Surrogate modeling for high-dimensional nonlinear dynamical systems that exhibit chaos requires mechanisms that preserve not only pointwise accuracy but also the scale-dependent structure of physical fields. Bandwise spectral power losses, such as the binned spectral loss function, provide such supervision on structured grids, where Fourier modes define a standard frequency decomposition. On irregular meshes, however, no canonical Fourier basis exists, and spectral representations must be constructed from graph operators induced by mesh connectivity and geometry. In this study, we extend the binned spectral power loss for application to unstructured-mesh surrogate modeling of nonlinear dynamical systems. This is obtained by replacing Fourier bands with graph-Laplacian frequency bands, and we provide scalable Chebyshev and multilevel approximations for improving long-horizon rollout fidelity. In its full-spectrum form, our approach uses graph Laplacian eigenspaces to provide a graph analogue of Fourier band-power matching, but incurs the high cost of spectral decomposition. As a scalable approximation, we replace exact band projectors with sparse Chebyshev polynomial graph filters, avoiding explicit eigendecomposition. When utilizing multilevel graph architectures, we introduce Graph Laplacian Energy Alignment for Meshes (GLEAM), which applies retained-subspace scale-aware supervision across graph hierarchies so that coarse and fine representations are regularized during autoregressive rollout. Our results show that the proposed spectral losses improve long-horizon rollout fidelity and preserve statistical invariants for the forecasting of turbulent flows on unstructured meshes, compared to deterministic baselines.
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