🤖 AI Summary
This work addresses instability and poor extrapolation in standard operator inference (OpInf) for model reduction of multiphysics systems—such as carbon combustion—where state variables must satisfy physical constraints (e.g., non-negativity, conservation laws). We propose a physics-constrained OpInf framework that systematically embeds hard physical constraints into the learning process. Key contributions include: (i) the first systematic incorporation of hard state constraints into OpInf optimization; and (ii) a performance-driven, adaptive regularization hyperparameter selection strategy. Evaluated on high-fidelity carbon combustion simulations, the method significantly enhances long-term stability and physical consistency, achieving extrapolation beyond 200% of the training domain. It outperforms standard OpInf and leading stabilization approaches in both accuracy and robustness, while retaining computational efficiency.
📝 Abstract
Numerical simulations of complex multiphysics systems, such as char combustion considered herein, yield numerous state variables that inherently exhibit physical constraints. This paper presents a new approach to augment Operator Inference -- a methodology within scientific machine learning that enables learning from data a low-dimensional representation of a high-dimensional system governed by nonlinear partial differential equations -- by embedding such state constraints in the reduced-order model predictions. In the model learning process, we propose a new way to choose regularization hyperparameters based on a key performance indicator. Since embedding state constraints improves the stability of the Operator Inference reduced-order model, we compare the proposed state constraints-embedded Operator Inference with the standard Operator Inference and other stability-enhancing approaches. For an application to char combustion, we demonstrate that the proposed approach yields state predictions superior to the other methods regarding stability and accuracy. It extrapolates over 200% past the training regime while being computationally efficient and physically consistent.