吉林大学学报(工学版) ›› 2024, Vol. 54 ›› Issue (4): 874-882.doi: 10.13229/j.cnki.jdxbgxb.20220611

• 车辆工程·机械工程 • 上一篇    下一篇

基于分层卷积自编码器的钝体湍流流场降阶分析

夏超1,2(),王梦佳1,2,朱剑月3(),杨志刚1,2,4   

  1. 1.同济大学 汽车学院,上海 201804
    2.同济大学 上海地面交通工具风洞中心,上海 201804
    3.同济大学?铁道与城市轨道交通研究院,上海 201804
    4.北京民用飞机技术研究中心,北京 102211
  • 收稿日期:2022-05-19 出版日期:2024-04-01 发布日期:2024-05-17
  • 通讯作者: 朱剑月 E-mail:chao.xia@tongji.edu.cn;zhujianyue@tongji.edu.cn
  • 作者简介:夏超(1988-),男,工程师,博士. 研究方向:空气动力学. E-mail: chao.xia@tongji.edu.cn
  • 基金资助:
    国家自然科学基金项目(51905381);上海市地面交通工具空气动力与热环境模拟重点实验室(23DZ2229029)

Reduced-order modelling of a bluff body turbulent wake flow field using hierarchical convolutional neural network autoencoder

Chao XIA1,2(),Meng-jia WANG1,2,Jian-yue Zhu3(),Zhi-gang YANG1,2,4   

  1. 1.School of Automotive Studies,Tongji University,Shanghai 201804,China
    2.Shanghai Automotive Wind Tunnel Center,Tongji University,Shanghai 201804,China
    3.Institute of Rail Transit,Tongji University,Shanghai 201804,China
    4.Beijing Aeronautical Science & Technology Research Institute,Beijing 102211,China
  • Received:2022-05-19 Online:2024-04-01 Published:2024-05-17
  • Contact: Jian-yue Zhu E-mail:chao.xia@tongji.edu.cn;zhujianyue@tongji.edu.cn

摘要:

本文采用了一种非线性的分层卷积自编码器,类比于本征正交分解的方法,可以对提取到的低维特征进行能量排序,同时又能在一定范围内达到更高的降阶性能。文中以雷诺数为20 000的三维圆柱钝体湍流尾迹流动为例,分析分层卷积自编码器对该流场的降阶能力,并与本征正交分解的结果作对比。同时,在此基础上延伸出组合模态的概念,并增加每一组低维潜在向量数,观察重构流场与原始流场的均方误差变化。结果表明,在分层层数及每层潜在空间向量数较少时,非线性的分层卷积自编码器相对于本征正交分解的方法对流场有更强的还原能力,但是其优势会随着层数和潜在向量数的增加而减弱。

关键词: 分层自编码器, 卷积神经网络, 钝体湍流尾迹, 降阶模型

Abstract:

In this study, a nonlinear hierarchical convolutional autoencoder (H-CNN-AE) is employed to sort the energy content of the latent vectors of AE, which is analogous to the method of proper orthogonal decomposition (POD), and at the same time result in better performance in terms of reduced-order modelling within limits. This method is applied to a turbulent wake behind a three-dimensional circular cylinder bluff body at Re=20 000. We assess the ability of H-CNN-AE with L2 error and compares it with the results of POD. Furthermore, the concept of grouping AE-modes is extended. We observe the change of mean square error between the reconstructed and the original flow when adding the number of latent vectors of each group. It is demonstrated that when the number of subnetworks and low-dimensional vectors in latent space of each subnetwork is small, H-CNN-AE has better capability to restore the flow field than POD. However, it is also found that the strength of H-CNN-AE will weaken with the increase of the number of subnetworks and latent AE modes and will even be inferior to POD under certain conditions.

Key words: hierarchical autoencoder, convolutional neural network, bluff body turbulent wake, reduced order model

中图分类号: 

  • U462

图1

传统卷积自编码器"

图2

分层自编码器"

图3

三维圆柱绕流算例"

表1

分层卷积自编码器网络结构"

网络层No.输出图形
Input1(192,384,2)
Input21(1)
Conv(f=16)1(192,384,16)
MaxPooling(192,384,16)
Conv(f=8)3(24,48,8)
MaxPooling(12,24,8)
Conv(f=4)1(12,24,4)
MaxPooling(6,12,4)
Conv(f=2)1(6,12,2)
Reshape1(144)
Dense4(64)
(32)
(16)
(1)
Concatenate1(2)
Dense4(16)
(32)
(64)
(144)
Reshape1(6,12,2)
Conv(f=2)1(6,12,2)
Upsampling1(12,24,2)
Conv(f=4)(12,24,4)
Upsampling3(96,192,8)
Conv(f=8)(96,192,8)
Upsampling1(192,384,8)
Conv(f=16)(192,384,16)
Conv(f=2)1(192,384,2)

图4

网络的训练误差"

表2

不同激活函数时均L2误差"

激活函数L2误差
softsign1.045
tanh1.094
Relu2.209

图5

H-CNN-AE与POD的重构结果对比"

图6

H-CNN-AE与POD的流向速度u模态对比"

图7

POD分解AE模态"

图8

不同n和ne下的流场重构L2误差"

图9

带四层子网络的流场重构L2误差"

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