Study On The Characteristics Of Aerodynamic Drag Reduction And Noise Reduction With Different Passive Control Devices

With the rapid development of automobile manufacturing and highway,the speed of cars is constantly increasing,the problems of aerodynamic drag and aeroacoustics be more and more prominent,it is more important that the research on aerodynamic drag and aeroacoustics reduction.Bionics has been widely studied and applied in aerodynamic drag and noise reduction as it was proposed,however,the mechanism of drag and noise reduction for bionic non-smooth surfaces remains to be explored.At present,there are few applications of porous media layer in automobile drag and noise reduction technology,under this background,based on the theory of automobile aerodynamics,combined with computational and computational aeroacoustics analysis method,the bionic non-smooth surface and porous media layer are attached to the Square Ahmed body base surface for studying the positive effect of these passive flow control devices on automobile aerodynamic and aeroacoustics,and the mechanism is explored.Firstly,the Square Ahmed simplified vehicle model was selected as the research object carrier,the existing wind tunnel test data was used to verify the reliability of the CFD numerical simulation result,at the same time,numerical simulations were carried out on the three grids with different resolutions,and the simulation results of the flow field parameters under the three grids were compared,the grid independence is verified,that is to say,the factor of grid resolution is excluded,which is a factor affects the simulation results.Secondly,three passive flow control devices,riblets,pits,and porous media layer,are applied,which are respectively arranged at base surface of the Square Ahmed body.The influence of these three flow control devices on the wake flow of the body by Computational Fluid Dynamic simulation.The flow field parameters of the model with the devices of non-smooth surface riblets,pits and porous media layers at the base are compared with the original model.By analyzing the drag coefficient,wake structure,average pressure,pressure coefficient,average velocity and Reynolds shear,the influence of three passive fluid control devices on the wake field is further analyzed,from the influence of friction resistance and pressure difference resistance,the drag reduction mechanism of different passive fluid control devices is analyzed.The results show that the devices of non-smooth riblets,pits and porous media layers at the end of the model can achieve a certain degree of drag reduction,with drag reduction rates of 2.6%,3.53% and 5.17%,respectively.Finally,the noise at the far-field monitoring point is analyzed by FW-H acoustic analogy method.Through the power spectral density analysis of the far-field noise and the directivity analysis of the total sound pressure level at the monitoring point,the influences of the riblets,pits and porous media layers on the surface of the model sound source are compared.Based on the analysis results of far-field aerodynamic sound field,the noise reduction mechanism of different passive flow control devices is analyzed from the reduction mechanism of turbulence burst intensity and bubble pulsation frequency.The results show that the devices of non-smooth grooves,pits and porous media layer at the base of the model can achieve certain noise reduction effect,and the maximum reduction values of the total sound pressure level are 2.636 d B,2.61 d B and 3.225 d B,respectivelyThis thesis analyzes the influence of different passive control methods on aerodynamic drag characteristics and aeroacoustics characteristics of simplified car models,and briefly explains the mechanism of drag reduction and noise reduction of different passive control methods,which has important engineering reference significance...