Recent advancements in operator-type neural networks have shown promising results in approximating the solutions of spatiotemporal Partial Differential Equations (PDEs). However, these neural networks often entail considerable training expenses, and may not always achieve the desired accuracy required in many scientific and engineering disciplines. In this paper, we propose a new Spatiotemporal Fourier Neural Operator (SFNO) that learns maps between Bochner spaces, and a new learning framework to address these issues. This new paradigm leverages wisdom from traditional numerical PDE theory and techniques to refine the pipeline of commonly adopted end-to-end neural operator training and evaluations. Specifically, in the learning problems for the turbulent flow modeling by the Navier-Stokes Equations (NSE), the proposed architecture initiates the training with a few epochs for SFNO, concluding with the freezing of most model parameters. Then, the last linear spectral convolution layer is fine-tuned without the frequency truncation. The optimization uses a negative Sobolev norm for the first time as the loss in operator learning, defined through a reliable functional-type \emph{a posteriori} error estimator whose evaluation is almost exact thanks to the Parseval identity. This design allows the neural operators to effectively tackle low-frequency errors while the relief of the de-aliasing filter addresses high-frequency errors. Numerical experiments on commonly used benchmarks for the 2D NSE demonstrate significant improvements in both computational efficiency and accuracy, compared to end-to-end evaluation and traditional numerical PDE solvers.

在这篇论文中，我们提出了一种新的空时傅里叶神经算子 (Spatiotemporal Fourier Neural Operator, SFNO)，它学习了 Bochner 空间之间的映射，并引入了一个新的学习框架来解决神经网络训练方面的问题。这种设计通过使用一种可靠的基于可估计（Parseval）误差分析的负 Sobolev 范数作为运算符学习的损失函数来优化神经算子，从而在处理低频误差和高频误差时取得了显著的计算效率和精度改进。与端到端评估和传统数值偏微分方程求解器相比，在二维 Navier-Stokes 方程常用基准测试中进行的数值实验显示出了显著的改进。

频谱精化：精调用于湍流流动的准确时空神经算子