Journal of Jilin University(Engineering and Technology Edition) ›› 2023, Vol. 53 ›› Issue (5): 1289-1296.doi: 10.13229/j.cnki.jdxbgxb.20210940

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Optimization on distortion grid of vehicle external flow field based on Laplacian Algorithm

Yong ZHANG1,2(),Feng-zhao MAO1,Shui-chang LIU1(),Qing-yu WANG1,Shen-gong PAN1,Guang-sheng ZENG1   

  1. 1.School of Mechanical Engineering，Hunan University of Technology，Zhuzhou 412007，China
    2.State Key Laboratory of Advanced Design and Manufacturing of Automotive Bodies，Hunan University，Changsha 410082，China
  • Received:2021-09-17 Online:2023-05-01 Published:2023-05-25
  • Contact: Shui-chang LIU E-mail:834130255@qq.com;289714423@qq.com

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Abstract:

In order to realize the high precision simulation of the vehicle external flow field， the grid distortion position is explored on the basis of analyzing the distortion grid quality evaluation criteria，with the simplified car model in actual use as the research object. In order to prevent the negative volume phenomenon caused by the deviation of the center node during the optimization of the volume mesh， the length weighted Laplacian algorithm is proposed to carry out the simulation calculation of the local optimization of the distortion grid， and verified by the test results of HD-2. The results show that the transition areas of the body side feature line，the front windshield and hood，the rear windshield and luggage lid are prone to volumetric grid distortion.The length weighted Laplacian algorithm can reduce the number of distorted grids， increase the simulation accuracy of the drag coefficient by 3.90%， and the error from the wind tunnel test is 2.26%.The simulation of vehicle tail flow field is more accurate than before the optimization compared with the PIV test， which shows the effectiveness of the length weighted Laplacian algorithm.

Key words: vehicle engineering, grid distortion optimization, Laplacian algorithm, CFD simulation accuracy, wind tunnel experiment

CLC Number: 

  • U461.1

Fig.1

Definition of aspect ratio of quadrilateral"

Fig.2

Definition of aspect ratio of triangle"

Fig.3

Definition of aspect ratio of tetrahedron"

Fig.4

Definition of triangle skew rate"

Fig.5

Definition of quadrilateral skew rate"

Fig.6

Global coordinates of any straight-sided quadrilateral element"

Fig.7

Failure diagram of Laplacian algorithm"

Fig.8

Schematic diagram of Laplacian optimization algorithm"

Fig.9

Model size of car model（Unit：mm）"

Fig.10

Computational domain of vehicle model"

Fig.11

Grid of longitudinal symmetry plane"

Fig.12

Tetrahedral mesh"

Fig.13

Prismatic grid"

Fig.14

Optimized tetrahedral and prismatic grids"

Table 1

Boundary conditions"

计算域边界边界条件设置
入口速度/(m·s-1)30
入口湍流强度/%0.5
水力直径/m2.496
压力出口/Pa1.01×105
出口湍流强度/%5
水力直径/m2.496
地面边界滑移壁面
车身壁面固定壁面
其余壁面对称壁面

Fig.15

PIV experiment site diagram"

Fig.16

Velocity flow charts of CFD simulation and velocity flow charts of wind tunnel experiment"

Fig.17

Velocity cloud images of CFD simulation and velocity cloud images of wind tunnel experiment"

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