基于A柱-后视镜车内气动噪声数值模拟与预测

针对后视镜引起的前侧窗与车内气动噪声问题,采用计算流体力学(CFD)方法对某商用车进行车外后视镜区域数值模拟和车内噪声预测的研究。稳态分析采用RANS模型中SST(Menter)k-ω模型,瞬态分析采用基于SST(Menter)k-ω的分离涡模拟(DES);通过分析后视镜侧窗区域的稳态静压力与瞬态动压力、速度和涡量云图,揭示了因A柱后视镜而产生车窗表面的湍流压力脉动的机理;同时求解瞬态流场获得两侧车窗表面湍流压力脉动载荷。采用声学FEM方法将车窗表面湍流压力脉动作为边界条件来计算气动噪声的传播,基于车内声学空间不同频率的声压级云图分布规律,说明了车内气动噪声主要集中在中低频段和声压级最大的分布区域;驾驶员左耳旁声压级曲线展示了20-2500 Hz频段内声压级变化规律。最后进行实车道路滑行测试,证实了气动噪声在车速80-110 km/h时较为明显的结论;采用CFD结合声学有限元的方法可较为准确地预测车内100-2500 Hz气动噪声的声压级,为优化后视镜、降低驾驶室内气动噪声提供仿真和试验的技术方案。

Numerical Simulation and Prediction of A-Pillar and Rear-view Mirror Induced Vehicle Interior Aerodynamic Noise

Aiming at the issue of front window and interior aerodynamic noise caused by rear-view mirror,the numerical simulation of exterior rear-view mirror region and prediction of interior noise in a commercial vehicle are studied by using computational fluid dynamics(CFD)method.The SST(Menter)k-ωmodel in RANS model is used for steady-state analysis,and the detached eddy simulation based on the SST(Menter)k-ωmodel is used for transient analysis.By analyzing the nephograms of steady static pressure and transient dynamic pressure,velocity and vorticity,the mechanism of turbulent pressure fluctuation of side window caused by A-pillar and rear-view mirror is revealed,meanwhile the transient flow field is solved to obtain the surface turbulent pressure fluctuation load on two side windows.Acoustic FEM method is adopted to calculate the propagation of aerodynamic noise with the turbulent pressure fluctuation on window surface as boundary condition.Based on the distribution law of sound pressure level nephogram of interior acoustic space at different frequencies,it is indicated that the interior aerodynamic noise is mainly concentrated in the middle and low frequency ranges and the maximum distribution region of sound pressure level,and the sound pressure level curve at driver's left ear exhibits the variation law of the sound pressure level in the frequency range of 20-2500 Hz.Finally,a real vehicle coasting road test is conducted,verifying the conclusion that the aerodynamic noise is more apparent at the speed range of 80-110 km/h.The adoption of CFD technique combined with acoustic FEM can relatively accurately predict the sound pressure level of interior aerodynamic noise at the frequency range of 100-2500 Hz,providing technical schemes of simulation and test for optimizing rear-view mirror and reducing cabin aerodynamic noise.