Title: Analysis and evaluation of CFD simulation uncertainty based on aerodynamic drag of the Ahmed car

Authors: Peng Li; Xiaoyu Yang; Sha Huang; Zhan Huang; Jiqiang Niu

Addresses: School of Rail Transport, Wuyi University, Guangdong, Jiangmen, 529020, China ' School of Mechanical Engineering, Southwest Jiaotong University, Sichuan, Chengdu, 610031, China ' School of Rail Transport, Wuyi University, Guangdong, Jiangmen, 529020, China ' School of Mechanical Engineering, Southwest Jiaotong University, Sichuan, Chengdu, 610031, China ' Key Laboratory of Conveyance and Equipment of Ministry of Education, East China Jiaotong University, Jiangxi, Nanchang, 330044, China; School of Mechanical Engineering, Southwest Jiaotong University, Sichuan, Chengdu, 610031, China

Abstract: To identify the key factors affecting aerodynamic drag prediction in the aerodynamic shape optimisation design of ground transportation, a quantitative and sensitivity analysis of aerodynamic drag uncertainty was conducted with the Ahmed car as the object. Grid size, turbulence model, pressure velocity coupling and spatial discretisation scheme are selected as variables, and their values are assumed. Then, an orthogonal experimental design scheme was used to calculate aerodynamic drag using the computational fluid dynamics (CFD) method. Multi-factor CFD uncertainty quantification and sensitivity analysis were conducted, and verified with wind tunnel experimental data. The results show that the degree of effect on the aerodynamic drag of the Ahmed car is in the order of spatial discretisation scheme, grid size, pressure velocity coupling, and turbulence model. The best simulation strategies for aerodynamic drag are: QUICK scheme, fine grid, SIMPLEC algorithm, and SST k-ω turbulence model.

Keywords: uncertainty analysis; Ahmed car; aerodynamic drag; CFD; computational fluid dynamics; grid independence.

DOI: 10.1504/IJHVS.2025.144163

International Journal of Heavy Vehicle Systems, 2025 Vol.32 No.1, pp.122 - 135

Received: 17 Jul 2023
Accepted: 24 Jul 2023
Published online: 30 Jan 2025 *

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