纵向间距对汽车三车队列气动阻力的影响

Effects of Longitudinal Spacing on 3-Vehicle Platooning Aerodynamic Drag

摘要:

以MIRA标准车型组（方背车S、快背车F和阶背车N）为研究对象，采用数值模拟研究纵向间距（0.1 L~1.0 L）统编（队列各车为同种车型）三车队列气动阻力的影响，并通过各部位压差阻力和流场分析，探究队列阻力变化的原因。结果表明：对于3种统编队列，整个队列的减阻量均是随着间距增大而不断减小，其中头车减阻量最大，其次是中车和尾车；头车减阻基本都随着间距增大而不断减小，归因于垂直尾部和后风窗背压回升的不断减弱；中车的方背车减阻量随着间距增大而逐渐减小，其他两车型均是在0.1 L~0.2 L减阻量大幅减小，随后基本保持较低减阻量不变；尾车的方背车减阻量同样随着间距增大而逐渐减小，在0.5 L后出现增阻，其他两车型减阻量基本较低并保持不变或有所增阻。以上阻力变化主要归因于不同间距下的尾迹低速流场改变导致的背压回升，以及前脸正压减弱、前缘圆角和A柱吸力减弱等的综合作用所致。

Abstract:

Based on the MIRA model group of full scale （squareback S， fastback F and notchback N）， numerical simulations are done to investigate the effect of longitudinal spacing （0.1-1L） on the uniform （vehicles in the platoon are the same） and ununiform （vehicles in the platoon are varied） three car platoon aerodynamic drag. Analyses of drag variation are conducted by pressure drag and flow field. The results indicate that the drag reduction of the three uniform platoons diminishes with increased spacing. The drag reduction of the head car dwindles basically with increased spacing， which is owing to the drop of backpressure recovery on the verticalbase and rearwindow. The drag reduction of squareback middle car declines gradually with increased spacing， that of other two configurations plunge rapidly in the spacing of 0.1-0.2L， then keep a low drag reduction. The drag reduction of squareback tail car also declines gradually with increased spacing， and experiences drag increase at the spacing 0.5L， other two configurations basically keep a low drag reduction or increase. the drag reduction of the three ununiform platoons also diminishes with increased spacing. The drag variations above are mainly resulted from the comprehensive effects of backpressure recovery， the impairing of positive pressure on the frontface and the crippling of negative pressure on the A-pillar and so on.