Experimental Investigation of Automotive Vehicle Transient Aerodynamics with a Reduced-Scale Moving-Model Crosswind Facility

Automotive vehicles operate in complex, transient aerodynamic conditions that can potentially influence their operational efficiency, performance and safety. A moving-model facility combined with a wind-tunnel is an experimental methodology that can be utilized to model some of these transient aerodynamic conditions. This experimental methodology is an alternative to wind-tunnel experiments with additional crosswind generators or actively yawing models, and has the added benefit of modelling the correct relative motion between the vehicle and the ground/infrastructure. Experiments using a VW Golf 7 were performed with a 1:10 scale model at the moving-model facility at DLR, Göttingen and a full-scale, operational vehicle at the BMW Ascheim side-wind facility. Successful functionality of the newly developed automotive-vehicle configuration of the moving-model facility - including the side wind-tunnel operation, rotating wheels in contact with the ground, and data-acquisition on-board the moving model - was achieved. Direct comparison of transient pressure at 24 locations across the front and rear bumpers and over the centerline of the vehicles show relatively good agreement between the two methodologies; establishing the moving-model facility as a viable reduced-scale methodology for investigating transient aerodynamics of automotive vehicles. Analysis of the time-resolved pressure measurements provides insight into the sensitivity of the surface pressure to transient crosswind; with indications that transient characteristics can only be captured with transient modelling of the crosswind-vehicle interaction.