Reduced-order modeling of pressure excitation on automotive front side window

Abstract

The pressure excitation on automotive front side window acts as an indicator of the unsteady flow and wind noise in the front side window region. The complex unsteady flow in this area generates a wider range of vortex structures resulting in the nonhomogeneous and complex pressure excitation on side glass. The description of the pressure field, which can consider the nonhomogeneous in the exact space, is needed to better solve the vibration and noise problems. The turbulent pressure excitation on side window was achieved by the incompressible improved delayed detached-eddy simulation, which is validated by the wind tunnel experiment. The reduced-order modeling methods, including the proper orthogonal decomposition and the dynamic mode decomposition, were employed to describe the pressure excitation on side glass. The dynamic mode decomposition modes separate the pressure excitation into three parts just corresponding to three main flow structures in the front side window region: the vortex shedding of the side mirror (lower frequency range), pedestal vortex (middle frequency range), and A-pillar vortex (higher frequency range). The turbulent pressure excitation generated by the vortex shedding of the side mirror contributes most of the vibration of the side glass and then the wind noise in the cabin in the low-frequency range. (The characteristic frequency is around 60 Hz, which is close to both the measured coincidence frequency and the theoretical derivation value.) The dynamic mode decomposition analysis with the unique and exact frequency for each mode, considering the nonhomogeneous of the pressure excitation, has potential to understand and solve the vibration and wind noise problems.

Comparison of hydrodynamic and acoustic pressure on automotive front side window

“…The numerical strategies of solving DES and acoustic wave equations based on APE have been used in previous works. 20 The resolution of time and space is the key to unsteady calculation and the key to solving the pressure fluctuation on the front side window. Based on the requirement of convergence, the Courant number becomes the link between the temporal resolution and the spatial resolution.…”

“…The hydrodynamic and acoustic pressure on the front side window were measured in the Aero-Acoustic Wind Tunnel (AAWT) in Shanghai Automotive Wind Tunnel Center (SAWTC). For details of the wind tunnel, readers can refer to Yuan et al 20 As shown in Figure 9(a), four surface microphones (Bru¨el & Kjaer 4949) were tapped on the outside surface of the front side window to measure the pressure fluctuation on the 2. According the discussion above, the efficient frequency range of the CFAT measurement here with the distance of the sensors D = 5 cm is (857, 3429) Hz.…”

“…The numerical strategies of solving DES and acoustic wave equations based on APE have been used in previous works. 20…”

“…The hydrodynamic and acoustic pressure on the front side window were measured in the Aero-Acoustic Wind Tunnel (AAWT) in Shanghai Automotive Wind Tunnel Center (SAWTC). For details of the wind tunnel, readers can refer to Yuan et al 20 As shown in Figure 9(a), four surface microphones (Brüel & Kjær 4949) were tapped on the outside surface of the front side window to measure the pressure fluctuation on the side glass, and the results can be used to validate the calculation of hydrodynamic pressure. As shown in Figure 9(b), 13 accelerometers (Kistler 8776A50) were installed on the inside surface of the front side window with an uniform distance to perform the CFAT measurement.…”

Numerical and experimental research on flow and aerodynamic noise characteristics of coach

“…Through investigations done on passenger car, the noise caused by the rearview mirror has been investigated at a certain extent. 5–9 Because of the difference mentioned above, the conclusion drawn from passenger car cannot be extended to coach. As a result, how to understand the aerodynamic noise of rearview mirror area of coaches is the focus of this study.…”