用扩散模型生成湍流长期预测,还能自适应选传感器位置。
Adaptive Diffusion Posterior Sampling for Data and Model Fusion of Complex Nonlinear Dynamical Systems
- 用多步自回归扩散模型提升长时预测稳定性。
- 在二维湍流和后向台阶流动中实现高维混沌系统预测与数据融合。
- 可动态规划传感器位置,无需重训模型即可融合观测数据。
高保真数值模拟混沌、高维非线性动力系统计算成本高昂,亟需高效代理模型。现有代理模型多为确定性,如神经算子,但难以捕捉混沌系统的内在分布不确定性。本文提出一种基于生成式机器学习的代理建模框架,采用深度扩散模型对湍流进行概率性长期预报。引入多步自回归扩散目标,显著提升长序列滚动预测的稳定性。针对复杂非结构化几何,采用多尺度图变压器架构,结合扩散预处理与体素网格池化。更重要的是,该框架统一实现了时空重要位置的传感器选址预测,可通过不确定性估计或误差估计模块完成。最后,利用扩散后验采样融合真实状态观测,无需重训练代理模型。在二维均匀各向同性湍流及后向台阶流中验证了该方法在预测、自适应传感器布置和数据同化方面的有效性。
原文摘要 · Abstract (English)
High-fidelity numerical simulations of chaotic, high dimensional nonlinear dynamical systems are computationally expensive, necessitating the development of efficient surrogate models. Most surrogate models for such systems are deterministic, for example when neural operators are involved. However, deterministic models often fail to capture the intrinsic distributional uncertainty of chaotic systems. This work presents a surrogate modeling formulation that leverages generative machine learning, where a deep learning diffusion model is used to probabilistically forecast turbulent flows over long horizons. We introduce a multi-step autoregressive diffusion objective that significantly enhances long-rollout stability compared to standard single-step training. To handle complex, unstructured geometries, we utilize a multi-scale graph transformer architecture incorporating diffusion preconditioning and voxel-grid pooling. More importantly, our modeling framework provides a unified platform that also predicts spatiotemporally important locations for sensor placement, either via uncertainty estimates or through an error-estimation module. Finally, the observations of the ground truth state at these dynamically varying sensor locations are assimilated using diffusion posterior sampling requiring no retraining of the surrogate model. We present our methodology on two-dimensional homogeneous and isotropic turbulence and for a flow over a backwards-facing step, demonstrating its utility in forecasting, adaptive sensor placement, and data assimilation for high dimensional chaotic systems.
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