Passenger Car Aerodynamic Noise Optimization Based On Sensitivity Identification

The increase of aerodynamic noise intensity with vehicle speed was much higher than that of other sound sources.When the vehicle speed reached100 km/h,aerodynamic noise becomes the main noise source of the vehicle.Compared with the traditional vehicles,the new energy vehicles lacked the masking effect of engine noise which intensify the aerodynamic noise.In order to reduce the aerodynamic noise in the vehicle,the aerodynamic noise of an SUV was taken as the research object.The fluid simulation software and acoustic simulation software were used to simulate the noise response by driver’s ear,and the simulation results were verified by wind tunnel test and road test.Firstly,the theory of analogue simulation and the establishment of analogue simulation model were expounded,and the boundary conditions,solving parameters,meshing and pre-processing of the flow field outside the vehicle were introduced in detail.Secondly,the flow field outside the vehicle was connected with the sound field inside the vehicle through the fluctuating pressure of the window,in order to simulate the process of aerodynamic noise spreading from the outside of the vehicle to the driver’s ear,and obtained the flow field outside the vehicle and the noise response by the driver’s ear.Then,the simulation results of the flow field outside the vehicle show that the aerodynamic noise depends on the intensity of the pressure fluctuation rather than the pressure amplitude,and the pressure fluctuation is more prominent in the area with large flow separation on the body surface.Finally,the simulation calculation of the driver’s ear noise was carried out,and the sound pressure level of the driver’s left ear is 67.27 dB(A),and the right ear is 66.29 dB(A).The simulation results were verified by the real vehicle road test,it is found that there is a certain difference between the test results and the simulation results,but it is mainly concentrated in the low frequency band,and the trend of the test results and the simulation results is the same,indicating that the simulation method can effectively reflect the driver’s ear noise.A sensitivity identification method of vehicle surface noise sources was proposed for the problem that the selection of design variables depends on engineering experience in current engineering optimization.With the Curle noise source as the objective,the discrete adjoint method was used to analyze the sensitivity of vehicle surface,and then the parts with higher sensitivity such as the rearview mirror,A pillar,hood and other parts were selected as the optimization area,which make the optimization of aerodynamic noise more effective and intuitive.The grid deformation technology was used to parameterize the optimized components,and 30 sample points were extracted by the Hamersley method to construct the proxy model,and the multi-island genetic algorithm was used for global optimization.The optimization results show that the maximum sound power level of the window surface decreases by 2 dB,and the sound pressure level response by the driver’s ear decreases by 0.7 dB(A).