Investigation of drag reduction technologies for light-duty vehicles using surface, wake and underbody pressure measurements to complement aerodynamic load measurements 2019-01-0644

In a multi-year, multi-vehicle study to quantify the aerodynamic drag changes associated with drag reduction technologies for light-duty vehicles, technologies were evaluated through full-scale testing in a large low-blockage closed-circuit wind tunnel equipped with a Ground Effect Simulation System (GESS) and a Road Turbulence System (RTS). This study was commissioned by Transport Canada and Environment and Climate Change Canada to support potential updates to light-duty vehicle greenhouse gas emission regulations. The technologies investigated include active grille shutters, production and custom underbody treatments, air dams, ride height control, side mirror removal and combinations of these. This paper focuses on mean surface, wake, and underbody pressure measurements recently introduced to complement aerodynamic force measurements. Surface pressures were measured by installing up to 40 surface pressure disks at strategic locations on four sedans and two small SUVs. Using a 2 m-high rake of 41 equally-spaced Pitot probes, wake total pressures were mapped in two cross-flow planes located from 0.1 to 0.4 vehicle lengths downstream of four sedans, two small SUVs, one minivan and one pick-up truck. A smaller rake of 4 to 6 Pitot probes was used to map underbody total pressures in one cross-flow plane downstream of the rear axle for 3 of these vehicles. The rakes were traversed laterally on 3 m-wide tracks. The results link drag reduction due to various technologies with specific changes in vehicle surface, rear underbody and wake pressures, and provide a database for numerical studies.