Numerical study of the flow-induced sunroof buffeting noise of a simplified cavity model based on the slightly compressible model

Abstract

Numerical computation was conducted to investigate the flow-induced sunroof buffeting noise at low Mach numbers. In order to avoid the stiffness problem which occurs in solving the compressible fluid equations at low Mach numbers, new governing equations were derived with the assumption that there is a slight compressibility effect. The mechanisms of the flow-induced sunroof buffeting noise were investigated by considering a three-dimensional model cavity. Extensive wind tunnel tests were conducted to verify the computational scheme developed in the present study. The results demonstrated that strong pressure fluctuations will be generated inside the cavity and that the modal resonant frequencies are in good agreement with the Rossiter formula and experimental data. Moreover, the results reveal that the sunroof buffeting noise is attributed to the periodicity of flow separation, vortex shedding, vortex impingement and pressure wave feedback, with the addition of the Helmholtz resonance locked effect. Therefore, the current computational approach was validated to have the capability to predict the flow-induced buffeting noise in low-Mach-number flows.

Control of Sunroof Buffeting Noise by Optimizing the Flow Field Characteristics of a Commercial Vehicle

“…Through the logarithmic operation to the sound pressure after the FFT operation, the sound pressure level result of the monitoring point can be obtained: SPL(dB) = 10 log 10 P( f ) P re f 2 (7) where P ref is the reference sound pressure related to the minimum sound pressure amplitude that can be heard by a human, and the value is 2 × 10 −5 Pa.…”

“…Oettle [6] used the Lattice Boltzmann method to evaluate the sunroof buffeting characteristics of a specific model of a vehicle, and the suppressing effect of the spoiler with or without the grid on the sunroof buffeting characteristics was analyzed. Wang [7] studied the mechanism of the sunroof buffeting noise at the speed of low Mach numbers based on a three-dimensional cavity model. The results showed that airflow separation, vortex shedding, vortex impact, periodic pressure wave feedback, and Helmholtz resonance are responsible for sunroof buffeting.…”

Research on wind buffeting noise characteristics of a vehicle based on ILRN and DES-ILRN methods

“…The simple model acoustic wind tunnel test was completed in the US Purdue University Herrick Low Noise Wind Tunnel. 21,22 The wind tunnel is a direct current, low speed, single test section acoustic wind tunnel, the length of the wind tunnel is 10.4 m, the total height is 2.3 m, the length of the wind buffeting noise test section is 1.23 m, the width of the test section is 0.53 m, and the height is 0.58 m. The test wind speed was set at 25 m/s. Figure 3 shows the cavity model and its installation.…”

Computational investigation and passive control of vehicle sunroof buffeting

“…During the last several years, some studies on buffeting were carried out by Gu et al, with part of the study focused on numerical investigations of automobile side window buffeting (Yang et al, 2014; Gu et al, 2015) and the other part of the study focused on numerical and experimental studies of 3D sunroof-like cavity buffeting (Wang et al, 2012, 2013). Based on a 3D sunroof-like cavity, numerical simulations were conducted at various velocities and showed good agreement with the wind tunnel measurements.…”