Research On Car External Flow Field And Aerodynamic Noise Based On Vortex Control

As a convenient travel tool,cars bring great benefits to people's lives.With the continuous development of the automotive industry,the evaluation standards of automobiles have attracted more and more attention.The ride comfort of a car is an important indicator.When the car is driving at a high speed,there will be strong aerodynamic noise outside the car,which will seriously affect the occupant comfort.It is an important way to improve the comfort of the driver and passengers for controlling and reducing the aerodynamic noise level.In this paper,vortex control principle was applied to establish vortex control structure-vortex generator on the A-pillar,B-pillar,C-pillar and roof.Numerical simulation method was used to study its influence on car external flow field and aerodynamic noise.The in-depth reading and summarization of domestic and foreign automotive exterior flow fields,external aerodynamic noise and vortex control related literature were conducted,relevant knowledge was learned,and relevant theories and research methods were mastered.In the simulation analysis of this paper,the standardk-wturbulence model was used in steady state and the large eddy simulation(LES)method was used in transient calculation state.Firstly,referring to the related literature,the vortex generators were built on a cylinder,and a streamline diagram of the airflow around the cylinder was obtained,and the control mechanism of the vortex generator on the flow field was analyzed.Based on the relevant wind tunnel test data of DrivAer model,the simulation was conducted.The pressure coefficient of the DrivAer body surface agreed well with the test,which verified the accuracy and reliability of the simulation method.Secondly,vertical,reverse symmetrical and horizontal vortex generators were built on the A-pillar of DrivAer model,and the simulation was carried out and compared with the original model.By comparing the total sound pressure curves of the front side window monitoring points of the 3 models with the original model,it is found that the Model 3 had a good noise reduction effect.Comparing the sound pressure level curves of the center frequency of 1/3 octave at the monitoring points of Model 3 and the original model,it was found that Model 3 had the effect of reducing the sound pressure level of the front side windows at most of the monitoring points.The analysis of the flow field in the front window region showed that the use of vortex generators which made the negative pressure generated in the A-pillar and front side windows increase and laminar flow transition to turbulent flow in advance.This slowed the dispersion of vortex,lengthen the process of vortex,and reduced the back pressure gradient of vortices.The horizontally arranged vortex generators were established on the B-pillar.The sound pressure level analysis of the rear window showed that Model 4 had good noise-reducing effects in addition to monitoring point 2.Flow field analysis showed that the use of vortex generators made the angle between the streamline and the incoming stream smaller,and the airflow was easier to pass through the body surface.The horizontally arranged vortex generators were established on the C-pillar.The simulation analysis showed that the sound pressure level curves were basically the same and the noise reduction effect on Model 5 was not obvious.Finally,vortex generators parallel to the flow direction were established on the roof of the DrivAer model.Simulation results showed that Model 6 using the vortex generator had a good noise reduction effect at most monitoring points.The analysis of the flow field in the rear windshield showed that the use of vortex generators increased the thickness of the boundary layer,making the air flow through the body surface have a sufficient buffer area on the surface of the rear windshield of the car,making the velocity gradient change smaller,so that pressure pulsation became smaller and aerodynamic noise was reduced.Conclusively,the vortex control structure vortex generator on the outer surface of a car body can reduce the aerodynamic noise to a certain extent,and the flow field outside the car body is improved.The research of this subject has certain reference and guidance significance for car shape design and aerodynamic noise reduction.