Aerodynamic Proximity Effects Between the DrivAer and AeroSUV Standard Models, Part 1 – Same-Lane Interactions

Road-vehicle platooning is traditionally defined as close-distance longitudinal following in laterally-aligned formation. In this paper, the effects of aerodynamic interactions on the drag of a two-vehicle system are examined by considering the influence of separation distance, cross winds, vehicle size and shape. Testing was undertaken at 30% scale in a large wind tunnel with road-representative freestream turbulence. Separation distances of 0.5, 1.0, and 2.0 vehicle lengths were examined over a range of yaw angles between ±15deg. A highlight of the current study is the characterization of platoon drag-reduction benefits for different sizes and shapes of the lead and follower models, by using a DrivAer model and an AeroSUV model, each with slant-back (Notchback or Fastback) and square-back (Estateback) variants, providing four distinct model pairings. Drag reduction for the lead model appears to be affected mainly by the size of the follower vehicle, while the follower model shows a much greater sensitivity to shape of the lead model. Larger drag reductions were observed at most distances and yaw angles when the lead model had a slant-back configuration (Notchback or Fastback), with smaller drag reductions observed for lead models with square-back configurations (Estateback). This resulted from the different wake structures and their respective influences on the surface-pressure distributions of the follower model. Thrust sheltering is observed as the dominant cause for increased drag at the shortest separation distance. Most of the data show that system-drag reductions were larger when the AeroSUV model followed the Drivaer model. This was due to a combination of the greater proportional drag reduction for the leading DrivAer and to the greater relative weighting of the AeroSUV drag reduction due to its larger reference drag area. Peak system-drag reductions of up to 22% were observed at 0.5L separation, decreasing to 18% at 1.0L and 12% at 2.0L. Note: Part 1 may be amalgamated with Part 2, due to significant overlap in frontmatter material, but an amalgamated paper may be too long, reaching up to 30 pages. Hence this two-part abstract submission, since retracting a paper is easier than adding a paper.