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基于卷积神经网络的结冰翼型气动特性建模研究

何磊1,钱炜祺2,董康生3,易贤4,柴聪聪5   

  1. 1. 中国空气动力研究与发展中心计算空气动力研究所;中国空气动力研究与发展中心空气动力学国家重点实验室
    2. 中国空气动力研究所与发展中心计算所
    3. 中国空气动力研究与发展中心计算空气动力研究所;
    4. 中国空气动力研究与发展中心
    5. 中国空气动力研究与发展中心空气动力学国家重点实验室
  • 收稿日期:2021-09-24 修回日期:2021-11-09 出版日期:2021-11-10 发布日期:2021-11-10
  • 通讯作者: 易贤

Aerodynamic characteristics modeling of iced airfoil based on convolution neural networks

  • Received:2021-09-24 Revised:2021-11-09 Online:2021-11-10 Published:2021-11-10
  • Contact: YI Xian

摘要: 提出了基于卷积神经网络(Convolutional Neural Networks,CNN)的翼型结冰气动特性预测方法,设计了输入层结冰翼型图像规范,克服了复杂冰形在翼面同一位置法线方向存在多值,单值函数难以描述的问题。预测模型可同时预测多个迎角对应的升阻力系数,实现了直接从冰形图像到气动特性的快速预测,对升力系数(CL)和阻力系数(CD)预测结果的平均相对误差均可控制在8%以内。重点研究了不同卷积层数量、卷积核数量、卷积核尺寸对模型性能的影响规律:CNN的不同层次特征对应不同滤波频率,卷积层数增加会捕获更多高频特征量;增加卷积核数量可提取更多冰形特征,提升模型性能,但数量过多会增加冗余特征,降低模型泛化性能;CD预测模型对卷积核数量的最低要求大于CL,其原因在于,相较CL,CD不仅受翼面压差影响,还受摩阻特性影响,其建模所需的关键特征数量需求多于CL;增大卷积核尺寸,可扩大卷积操作“视野”,增强对冰形整体特征信息的提取,有利于提升模型泛化性能。相关结论为飞机结冰气动特性实时动态预测与监测提供了新的思路和方法支撑。

关键词: 飞机结冰, 气动特性, 机器学习, 深度学习, 卷积神经网络

Abstract: A prediction method of iced airfoil aerodynamic characteristics is proposed based on the convolutional neural networds (CNN). This new method is able to solve the multiple-value problem of the complex ice shape along the wall-normal direction at a specific location of the airfoils. The CNN prediction model can predict the lift and drag coefficient at multiple angle of attacks by a rapid process from iced airfoil image to aerodynamics characteristics directly. The relative mean errors of the resulting lift coefficient (CL) and drag coefficient (CD) is less than 8%. By comparison, the influence of number of convolutional layers, number of convolutional filters and convolutional filter size on the model performance was investigated.The features of different layers in CNN correspond to different filter frequency, increasing number of convolutional layers will capture more features of high frequency. When increasing the number of filters,more features of ice shape will be extracted and the performance of model will be promoted. However, there will be more redundant features if the number of the filters exceed a critical value, which results in degration of the generalization performance.The required number of filters for predicting CD is higher than that of CL. This is because of the effects of characteristics of friction on CD are even more pronounced, so the number of key features requied to predicting CD is higher than that of CL. Moreover, larger size of filters will widen the field of view of convolution operation. Consequently, the capability of extracting global features will be enhanced, which will promote the generalization performance of the model. The current new method can be applied to the real-time prediction and monitor of aerodynamic characteristic of aircraft icing.

Key words: aircraft icing, aerodynamic characteristics, machine learning, deep learning, convolutional neural networks

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