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基于神经算子的湍流模拟方法

NEURAL OPERATOR-BASED SIMULATION METHODS FOR TURBULENT FLOWS

  • 摘要: 湍流普遍存在于航空航天、海洋、气象和工业过程等领域. 近年来, 随着机器学习方法的快速发展, 各种基于神经网络的湍流建模方法被逐步提出并得到了验证. 通过神经网络对流场的非稳态时间演化过程进行直接建模, 以替代计算成本较大的计算流体力学(CFD)模拟, 正成为一个热门方向, 而神经算子方法是该方向中的一个重要工具. 本文对机器学习方法在流体力学领域的应用方向进行了简要概括, 并重点介绍了利用神经网络对流场演化进行直接预测这一研究方向. 接下来, 结合课题组近期的研究成果, 重点介绍了神经算子方法在湍流预测领域的研究进展: 依次介绍了傅里叶神经算子(FNO)、Transformer神经算子和物理信息神经算子(PINO)在均匀各向同性湍流、自由剪切湍流、瑞利泰勒湍流和槽道湍流的快速预测方面的研究进展. 结果表明, 训练好的神经算子模型, 具有比传统大涡模拟(LES)方法更高的计算精度和计算效率. 这些结果展现了神经算子方法在湍流预测领域的潜力. 最后展望了未来值得关注的研究方向, 包括复杂流场的快速预测、模型的泛化能力、物理信息机器学习以及神经算子的理论分析等.

     

    Abstract: Turbulent flows are ubiquitous in aerospace, oceanography, meteorology, industrial processes and many other fields. In recent years, with the rapid development of modern machine-learning (ML) methods, various neural network (NN)-based turbulence modeling approaches have been proposed and validated. Among these approaches, directly modeling the unsteady temporal evolution of turbulent flow fields through NNs to replace the computationally expensive computational fluid dynamics (CFD) simulations has become a hot research direction recently, and the neural operator (NO) method is becoming an important tool in this field. The current paper focuses on ML-driven flow field prediction methods and, based on the recent works of our research group, provides an overview of the recent advancements in neural operator methods for rapid predictions of turbulent flows. First, we briefly summarize the application directions of ML techniques in fluid mechanics, with a focus on introducing several commonly used ML frameworks for the direct prediction of flow field evolution using neural networks. Next, integrating our group’s research efforts in recent years, we highlight the progress of neural operator methods in the field of turbulence prediction. Specifically, we discuss the research advancements in the application of Fourier neural operators (FNO), Transformer neural operators and physics informed neural operators (PINO) to the flow field prediction in homogeneous isotropic turbulence, turbulent mixing layer, Rayleigh-Taylor turbulence, and turbulent channel flows. In the numerical experiments for various types of turbulence, we found that well-trained neural operator models exhibit higher computational accuracy and efficiency compared to traditional large-eddy simulation (LES)-based CFD methods. These results demonstrate the enormous potential of neural operator-based ML methods in the field of turbulence prediction. Finally, the paper discusses future research directions worthy of attention, including the fast prediction of more complex turbulent flows, the model generalization capability, the embedding of fluid physics, and the theoretical analysis of neural operators.

     

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