| With the continuous breakthrough of automobile production and the shortage of petroleum resources and environmental problems in the world,the fuel consumption caused by the aerodynamic drag of automobile vehicles has been paid more and more attention,so it is essential for the aerodynamic drag reduction of automobile vehicles.At present,the drag reduction optimization of the whole vehicle is mainly concentrated on the upper surface of the vehicle body,but it has become difficult to carry out better optimization.Studies have shown that the wheel accounts for about 25% of the aerodynamic drag of the vehicle,but there is no detailed study of the wheel in engineering,especially in the domestic and international literature,considering that the wheel has the same rotation conditions as the real road condition.In the previous research,due to experimental conditions,most of the vehicle aerodynamic experiments didn’t consider the wheel rotation,which led to a huge difference from the actual road conditions;in CFD simulation,considering the wheel rotation is only using the MRF method,and did not make The wheel grids all really rotate.In the earlier time,this paper realizes the same wheel rotation simulation as the real working condition.The STAR-CCM+ software overlap grid zero gap technology is used to realize the zero-gap tangential rotation of the wheel and the calculation domain ground,which truly rotates the wheel to the ground and analyzes the simplified wheel rotation.The aerodynamic characteristics and flow field characteristics under the conditions and the difference between the flow field and the presence or absence of the boundary layer.It is found that there is a pair of vortexes similar to the Karman vortex motion near the ground of the rotating wheel wake,which has a good correlation with the wheel rotation period of only 37.5%.After joining the ground,the Magnus effect of the wheel is significantly weakened,and the lift of the wheel is increased.After the ground layer does not consider the influence of the boundary layer,the airflow near the ground accelerates significantly,resulting in an increase in the near-ground vortex flow rate.This also indicates the necessity of wheel rotation and the importance of ground effect,whether it is the wind tunnel test or CFD simulation,and whether the ground boundary layer is added.In this paper,the comparative analysis of the simplified wheel model in static and rotating conditions,as well as the comparison of wheel suspension and presence or absence of ground boundary layer conditions,respectively,summarizes the aerodynamic characteristics and filed characteristics of the wheel rotation and considering the ground effect conditions.Then,several key geometric feature sizes of real wheels are designed and their aerodynamic characteristics are analyzed.The key geometric features selected in this paper are mainly three types:(1)The different opening areas of the wheel rim.(2)The wheel rim has a positive and reverse rotation condition of the blade type wheel for suction.(3)Three types of tire treads in which the tire is longitudinally,laterally and transversely.The results show that the first time the rim opening is reduced,the aerodynamic force and the flow field change obviously;the positive and negative rotational aerodynamic forces and the flow field of the fan-blade rim are significantly different,and the reverse rotation is more favorable for the hot gas discharge in the wheel.The three-pattern aerodynamics and isosurface map of the tire can be seen that the horizontal stripes play a leading role in the wheel flow field.This provides an effective reference for the subsequent vehicle and the aerodynamic drag reduction of the wheel. |
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