Interior Prediction And Improvement Of Aerodynamic Noise Based On FEM

The level of vehicle interior noise is an important index to judge the ride comfort,and with the increase of vehicle speed,aerodynamic noise gradually becomes the main contributor to the level of vehicle interior noise.Through understanding the research results of domestic and foreign scholars,it is found that the current research methods of aerodynamic noise inside the vehicle mainly include boundary element method,finite element method and statistical energy method.The advantage of the boundary element method is mainly reflected in solving the acoustic problems in unbounded areas.The statistical energy method mainly studies the noise in the middle and high frequency band.Finite Element Method is mainly used to study the noise level of in the middle and low frequency band,which is more sensitive to human ears,while the sound energy of automobile interior noise is mainly concentrated in the middle and low frequency.Therefore,this paper uses Finite Element Method to predict the level of aerodynamic noise in the car.The CFD coupled with acoustic solver(FEM)calculation method is used in this paper to verify the simulation and experimental data of the flow field and internal and external sound field of the modern standard model(HSM),it is found that they have good consistency in the variation trend of sound pressure level with frequency,which proves the effectiveness and feasibility of using this method to study the interior noise level.Therefore,this paper adopts the above simulation method to analyze the external flow field and the internal and external sound field of a certain vehicle model code-named TMS in the 140km/h working condition.The steady-state simulation analysis mainly focuses on the flow phenomenon on the car body surface.Since the aerodynamic noise is mainly introduced into the car through the side window glass,the distribution of pressure and velocity field on the car window,including column A and the rearview mirror area,is explored.The analysis of transient flow focuses on the pressure pulsation in the surface area of the window at different times,especially the relationship between the pressure fluctuation at each monitoring point and the level of the sound pressure level there.In the analysis of the sound field,the direct calculation method is used to calculate and analyze the sound pressure of the monitoring points outside the vehicle,A-pillar,rearview mirror and the surface of the window.Then the interior noise level is calculated by using the finite element method and the interior noise level and the sound pressure distribution on the window glass are analyzed emphatically.Through the analysis of the model flow field and the internal and external sound field,different improvement schemes are proposed from the three directions of the generation,propagation and reception of wind noise,namely,thinning mirror handle,adding convex features at the side window,using ordinary sandwich glass,organic sandwich glass,and using different interior sound absorbing materials for combined calculation.According to the distribution of sound power level of the convection field and the dipole of the external sound field,as well as the comparison of the sound pressure level curve of the driver's left ear,the above schemes can reduce the interior noise level by 0-2d B to different degrees,the reduction has reached the initial purpose of noise reduction,and it has certain reference significance for the later application of this method for the study of aerodynamic noise in automobile vehicles.