He Yinzhi*; Wan Rongxin; Liu Yongming; et al. Transmission Characteristics and Mechanism Study of Hydrodynamic and Acoustic Pressure through a Side Window of DrivAer Model Based on Modal Analytical Approach, Journal of Sound and Vibration, 2021, 501: 116058. SCI.

Transmission characteristics and mechanism of the exterior wall pressure fluctuations (WPFs) on the side window of a DrivAer model to the interior wind noise were studied. After separation of hydrodynamic and acoustic pressure components with compressible CFD simulation and wavenumber decomposition (WND), an improved modal analytical approach was employed to calculate cabin interior noise with a simplified plate-cavity equivalent model. The simulation result was then validated through comparison with wind tunnel test. With the help of the analytical model, transmission loss (TL) of the exterior WPF to the interior noise was calculated with two sub-processes to study transmission efficiency and corresponding mechanism of the two pressure components. The result shows that hydrodynamic pressure loses much more energy than that of the acoustic pressure. The difference of transmission efficiency of the two pressure components is influenced by three main factors: “modal preference effect”, resonance effect and the coupling characteristic between modes of the side window and the cabin, especially the first two factors make the side window acting as a “low-wavenumber filter” for exterior WPF and form the primary causes for the transmission difference. Additionally, the generation of the coincidence effect was discussed from the perspective of modal analysis, indicating that it is essentially a particular resonance phenomenon, with the coincident wavenumber of excitation and structure.

 Based on an improved modal analytical approach, transmission characteristics and mechanism of the exterior hydrodynamic and acoustic pressure on the side window of a DrivAer model to the interior wind noise were clearly interpreted.

Fig. 8. The simplified plate-cavity equivalent model

Fig. 8. 简化后的平板-声腔等效模型

Fig. 13. TL of the exterior hydrodynamic and acoustic pressure to the interior noise (dB, Ref =Pa)

The different transmission efficiency of hydrodynamic and acoustic pressure is influenced by three main factors: “modal preference effect”, resonance effect and the coupling characteristic between modes of the window and the cabin, especially the first two factors make the side window acting as a “low-wavenumber filter”. From the perspective of modal analysis, the generation of the coincidence effect was discussed. It is indicated that it is essentially a particular resonance phenomenon, with the coincident wavenumber of excitation and structure.

Fig. 16. Vibration energy distribution on the side window modes (a) Excited by the hydrodynamic and acoustic pressure, (b) Excited by the acoustic pressure (dB, Ref = 1mm)

Fig.18. (a) Transmission efficiency of the WPF in wavenumber-frequency spectrum (dB, Ref = 1), (b) The hydrodynamic and acoustic pressure energy distribution in wavenumber-frequency spectrum (dB, Ref = Pa)