Study On Simulation And Control Method For Wind Noise Of Vehicle Rear Windows

With the rapid development of automotive technology and improvement of road condition, vehicle speed rises continuously. During a vehicle running at a high speed, for demisting or ventilating, the vehicle windows often need to be opened. This inevitably leads to some low-frequency and high-intensity wind noises(also called wind buffeting noise) in the passenger compartment. The noise makes the people inside the compartment tired and irritable easily if it lasts for a long time, thereby a bad ride comfort of the vehicle. Meanwhile, the wind noises may be radiated to surroundings, and cause noise pollution in the environment. The previous studies suggest that the wind noises from the rear windows is higher than those the front ones. Therefore, it is very important to further study and control the wind noise of vehicle rear window.Due to the continuous improvement of computer performance and aero-acoustic theories, it is now possible to study the wind noises of a vehicle using the numerical simulation method. In this thesis, based on the large eddy simulation(LES) and Lighthill analogy theories, wind noises of vehicle rear window are investigated by using a hybrid simulation method(HSM). The HSM is performed in the CFD software FLUENT and acoustic software ACTRAN. Firstly, the HSM accuracy in both the far-field and near-field simulations of wind noises are verified by the models of the flow around a circular cylinder and the flow over a cavity. The frequency bandwidth of interest is determined through spectra analysis of the measured interior wind noises from the road tests of a real vehicle. Based on the established simulation models of the vehicle, some influence factors on the wind noise, such as the vehicle speed, degree of window opening and the number of opened windows, are investigated. Furthermore, we attempts to attach sound absorbing materials inside the compartment or install column at the suitable position of window opening to control the wind noises. And column’s impacts on the surrounding environment are also analyzed.The study results suggest that, the HSM has a high precision in simulation of wind noise of vehicle rear window. The error of sound pressure level(SPL) is less than 2.7%. The SPL of wind noise is positively correlated to the vehicle speed, which reaches maximum at 42% opening of the rear window. The wind noise of opening two rear windows is lower than that of opening one. Sound-absorbing materials have a little contribution on wind-noise reduction. After installing column at the opened rear window, reduction of wind noise reaches to 21.5%, as well as a reduction of the noise pollution in the surroundings. The optimal combination of the column’s position, width and thickness obtained by the orthogonal tests shows that wind noise is reduced 1.46 d B. Conclusions can be drawn that the proposed HSM and the wind-noise control measures are correct and effective, which can be extended to other types of vehicle and is instructive for wind-noise control of vehicles in engineering.