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When a commercial vehicle is driving with the sunroof open, it is easy for the problem of sunroof buffeting noise to occur. This paper establishes the basis for the design of a commercial vehicle model that solves the problem of sunroof buffeting noise, which is based on computational fluid dynamics (CFD) numerical simulation technology. The large eddy simulation (LES) method was used to analyze the characteristics of the buffeting noise with different speed conditions while the sunroof was open. The simulation results showed that the small vortex generated in the cab forehead merges into a large vortex during the backward movement, and the turbulent vortex causes a resonance response in the cab cavity as the turbulent vortex moves above the sunroof and falls into the cab. Improving the flow field characteristics above the cab can reduce the sunroof buffeting noise. Focusing on the buffeting noise of commercial vehicles, it is proposed that the existing accessories, including sun visors and roof domes, are optimized to deal with the problem of sunroof buffeting noise. The sound pressure level of the sunroof buffeting noise was reduced by 6.7 dB after optimization. At the same time, the local pressure drag of the commercial vehicle was reduced, and the wind resistance coefficient was reduced by 1.55% compared to the original commercial vehicle. These results can be considered as relevant, with high potential applicability, within this field of research.

The aim of this study was to reduce the aerodynamic resistance coefficient of heavy commercial vehicles and buffeting noise that occurs when a sunroof is opened. Computational fluid dynamics was used to establish a numerical simulation model of wind resistance and buffeting noise. Analysis shows that the main influences on aerodynamic resistance are the airflow impact on the roof dome and the wake vortex behind the cab. Sunroof buffeting noise is caused by a low-pressure turbulent vortex generated at the forehead of the cab and falls off at the sunroof. A strategy for reducing the wind resistance coefficient and sunroof buffeting noise is proposed, which involves optimizing the sun visor installation angle and roof dome shape. The optimal strategy is to increase the sun visor installation angle by 4° and use the Scheme 2 roof dome. After optimization, the aerodynamic resistance coefficient of the commercial vehicle was reduced by 2.07% and the sound pressure level of sunroof buffeting noise was reduced by 18.3 dB. Hence, the effect of optimization was obvious. This work provides guidance for reducing drag and buffeting noise in commercial vehicles.

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