Wind-Load and Surface-Pressure Measurements of the Aerodynamic Interactions of a Passenger Vehicle with Adjacent-Lane Vehicles

The mutual aerodynamic influence of road vehicles in close proximity is known to alter significantly the drag performance of the vehicles. This paper presents an extended analysis from a study of two open-access road-vehicle shapes (a DrivAer Notchback model and an AeroSUV Estateback model) in close lateral proximity with each other, or with other vehicle shapes. Wind-tunnel measurements were conducted for a yaw-angle range of ±10°, for lateral distances representing 75%, 100%, and 125% of a typical highway lane spacing, and for longitudinal distances up to 2 vehicle lengths forward and back. The results of a previous analysis of the data, which examined aerodynamic force measurements only, showed changes in drag coefficient of ±20% or more depending on the relative locations and wind conditions. In this paper, the force-coefficient results reexamined, and surface-pressure measurements are introduced to investigate the sources of the performance changes. The results suggest that the changes in aerodynamic performance of vehicles in close lateral proximity arise from three mechanisms: 1) from a combination of locally-reduced static pressure, due to the combined blockage effect of the two vehicles on the local flow field; 2) from local flow-angularity changes altering the effective yaw angle of each vehicle; and 3) from wake-body interactions. The results also demonstrate a small increase in proximity effect when a proximate Ahmed body is introduced instead, likely as a results of its larger internal volume, but with trends that match the DrivAer/AeroSUV results. Proximity-induced loads and pressures are shown to increase with reduced distance and with increased adjacent-body size.