用残差学习提升非定常气动载荷预测精度,融合物理模型与神经网络。
A Residual Learning Approach for Unsteady Aerodynamic Load Prediction
- 以沃格纳模型为基础,让神经网络学习误差残差,降低学习难度。
- 残差模型在多种运动类型下误差更低,且训练稳定性更好。
- 适合需要高鲁棒性的气动弹性仿真,尤其对复杂运动泛化性强。
本文研究了残差学习在气动弹性应用中提升非定常气动载荷预测的可行性。采用长短期记忆(LSTM)神经网络处理具有气动记忆效应的序列数据,以NLR 7301机翼为基准,在跨音速流动下针对指定俯仰和上下运动的高保真CFD升力数据进行测试。以基于沃格纳函数的解析模型作为物理基线,神经网络学习的是CFD升力系数与沃格纳预测值之间的残差。将该残差模型与直接预测CFD升力的神经网络模型进行对比,涵盖特征选择、归一化、外部基准案例及留一法、留族法泛化测试,覆盖正弦与非正弦运动。结果显示,当输入与沃格纳变量对齐时,残差模型整体误差更低且训练表现更一致;尽管直接模型在部分高频情形下更精确,但残差模型在留一法和留族法测试中泛化能力更强,剔除整个运动族后误差增加更小。结果表明,残差学习作为模块化方法,能有效增强经典低阶气动理论,尤其在物理基线已去除结构化响应后,使神经网络只需学习低方差修正项。
原文摘要 · Abstract (English)
This paper investigates the feasibility of using residual learning to improve unsteady aerodynamic load prediction for aeroelastic applications. The machine learning technique selected for the study is the long short-term memory (LSTM) neural network, which is used for its suitability for sequential data with aerodynamic memory effects. The approach is investigated for the NLR 7301 airfoil benchmark using high-fidelity CFD lift data for prescribed pitch and plunge motions in the transonic flow regime in the presence of shock motion. An analytical unsteady aerodynamic model based on the Wagner function is used as a physics-based baseline, and the neural network is trained to learn the difference between the CFD lift coefficient and the Wagner prediction. The residual model is compared with a direct neural-network model trained to predict the CFD lift coefficient. The comparison includes feature and normalization studies, external benchmark cases, and leave-one-out and leave-family-out generalization tests across a range of sinusoidal and non-sinusoidal motions. The residual model performs best when its inputs align with the Wagner formulation variables, generally giving lower error and more consistent performance across training runs, though the direct model remains more accurate for some high-frequency cases. The residual model also generalizes better in the leave-one-out and leave-family-out tests, with a smaller increase in error than the direct model when entire motion families are withheld from training. Overall, the results indicate that residual learning shows promise as a modular approach for augmenting classical low-order aerodynamic theories, especially when the physics baseline removes a structured part of the aerodynamic response and leaves a lower-variance correction for the neural network to learn.
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