Numberical Simulation Of Hydrodynamic Noise Generated By Driving On The Wet Road Surface

With the continuous increase of automobile quantity in China,the harm of driving noise is more and more serious,which has become the main noise source.Especially when there is water on the road,the traffic noise shows a trend of louder and higher frequency.Some parts of China are in the monsoon climate zone,the annual rainfall is abundant,the traffic noise on the pavement with water film cannot be ignored.The traffic noise on the pavement with water film mainly includes vibration noise and hydrodynamic noise.The sound principle of vibration noise is consistent with that of dry road surface.Therefore,this paper mainly studies the hydrodynamic noise generated by the pavement with water film from the theoretical and numerical simulation perspectives.The main work includes:1.The basic theory and calculation method of hydrodynamic noise generated by running on the pavement with water film.Based on the sound principle of hydrodynamic noise,it is clear that the pulsating pressure of water film and air acting on the tire surface is the dipole sound source of the noise.The theoretical formula of noise prediction is established based on the actual boundary conditions of vehicles running on the pavement with water film,and the hybrid calculation method is selected.2.Fluid-structure interaction of tire-pavement-water film based on Abaqus CEL.In this paper,the three-dimensional model of the tire is established and the force characteristics are verified.The tire model is applied to the fluid-solid coupling model of the tire-road-water film,and the deformation model of the tire rolling on the water surface is obtained.Based on this model,the computational domains of flow field and sound field are obtained respectively by using Boolean subtraction operation.3.Numerical calculation of the external flow field and dipole sound source of the tire when driving on road which covered with water film.Based on the method of large eddy current simulation,the hydroplaning speed of tires which is calculated under the conditions of partition of flow field computation domain,mesh division and boundary,is compared with the experienced hydroplaning speed to verify the rationality of the flow field model.Ffowcs Williams and Hawkings equation was used to calculate and output the pulsating pressure on the tire wall as the sound source information for the calculation of sound field.4.Finite element calculation of noise.Fast Fourier transform is used to transfer time domain sound source information into frequency domain sound source information.The acoustic calculation is carried out by the acoustic finite element method and the automatic matching layer technique.On the premise of a certain flow,the sound pressure level curve begins to stabilize after the middle frequency band of about 1000 Hz.In the middle and high frequency band,the sound pressure level value of the inlet direction is larger than that in the outlet direction.The sound field is bidirectional and has dipole character.The variation trends of sound pressure level frequency curve at different water film thicknesses are basically the same,ae well as the directivity of the external radiation sound field.When the water film thickness is large,the hydrodynamic noise occupies the dominant position of the hydrodynamic noise.At this point,the sound pressure level value of hydrodynamic noise is significantly higher than that of dry road surface,when the water film thickness is 10 mm,the sound pressure level value of hydrodynamic noise is more than twice that of dry road surface,when the water film thickness is 5mm,the sound pressure level value of hydrodynamic noise is about 1.5 times that of dry road surface.The size of sound pressure level increases with the increase of water film thickness.Because water occupies a small volume fraction in the whole model,even if the water film thickness is 10 mm,the volume fraction of water is only 1.59%,the increase of water film thickness has no significant effect on the increase of sound pressure level.When the water film thickness is 10 mm,the sound pressure level value of hydrodynamic noise is about 1.3 times of that of dry road surface.When the water film thickness is 5mm,the sound pressure level value of hydrodynamic noise is about 1.2 times that of dry road surface.The research results in this paper will provide an acoustic detection method for driving safety warning in rainy days,which is different from driving speed and mechanical response...