Effects of Longitudinal Spacing on 3-Vehicle Platooning Aerodynamic Drag

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.

Key words:vehicles platooning;aerodynamic drag reduction;MIRA model group;wake