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arXiv 2101.04879cs.CEcs.LGphysics.comp-ph
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不确定性量化偏微分方程弱解的贝叶斯神经网络

Bayesian neural networks for weak solution of PDEs with uncertainty quantification

University of Michigan(密歇根大学)

Xiaoxuan Zhang, Krishna Garikipati

摘要:

求解偏微分方程(PDE)是理解物理系统行为的经典方法。然而,使用最先进的离散化技术的偏微分方程的大规模解决方案仍然是一个昂贵的命题。在这项工作中,提出了一种新的物理约束的神经网络(NN)的方法来解决没有标签的偏微分方程,以期实现高通量的解决方案,支持设计和决策。与现有的物理通知NN方法不同,其中强形式或弱形式的PDE用于构造损失函数,我们通过一个有效的,基于卷积运算符的离散化残差的PDE和矢量化的实现编写NN的损失函数。我们探索了确定性和概率模型的编码器-解码器NN结构,后者使用贝叶斯NN(BNN),这使我们能够量化模型参数的认知不确定性和数据中噪声的任意不确定性。对于BNN,离散残差用于构造似然函数。在我们的方法中,确定性和概率卷积层都用于学习应用的边界条件(BC)并检测问题域。由于Dirichlet和Neumann BC都被指定为NN的输入,因此单个NN可以解决类似的物理问题,但具有不同的BC和许多问题域。经过训练的代理PDE求解器还可以对它们在训练期间未暴露的BC进行内插和外推(在一定程度上)预测。这种代理模型对于需要多次重复求解类似类型的偏微分方程而又略有变化的问题尤为重要。我们证明了所提出的框架的能力和性能,将其应用到稳态扩散,线性弹性和非线性弹性。

英文摘要:

Solving partial differential equations (PDEs) is the canonical approach for understanding the behavior of physical systems. However, large scale solutions of PDEs using state of the art discretization techniques remains an expensive proposition. In this work, a new physics-constrained neural network (NN) approach is proposed to solve PDEs without labels, with a view to enabling high-throughput solutions in support of design and decision-making. Distinct from existing physics-informed NN approaches, where the strong form or weak form of PDEs are used to construct the loss function, we write the loss function of NNs based on the discretized residual of PDEs through an efficient, convolutional operator-based, and vectorized implementation. We explore an encoder-decoder NN structure for both deterministic and probabilistic models, with Bayesian NNs (BNNs) for the latter, which allow us to quantify both epistemic uncertainty from model parameters and aleatoric uncertainty from noise in the data. For BNNs, the discretized residual is used to construct the likelihood function. In our approach, both deterministic and probabilistic convolutional layers are used to learn the applied boundary conditions (BCs) and to detect the problem domain. As both Dirichlet and Neumann BCs are specified as inputs to NNs, a single NN can solve for similar physics, but with different BCs and on a number of problem domains. The trained surrogate PDE solvers can also make interpolating and extrapolating (to a certain extent) predictions for BCs that they were not exposed to during training. Such surrogate models are of particular importance for problems, where similar types of PDEs need to be repeatedly solved for many times with slight variations. We demonstrate the capability and performance of the proposed framework by applying it to steady-state diffusion, linear elasticity, and nonlinear elasticity.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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