Affiliations: Mechanical Engineering, Graduate School, Sunchon
National University, 315 Maegok, Suncheon Jeonnam 540-742, Korea | School of Mechanical and Aerospace Engineering,
College of Engineering, Sunchon National University, 315 Maegok, Suncheon,
Jeonnam 540-742, Korea. E-mail: ksc@sunchon.ac.kr | Department of Mechanical Engineering, College of
Engineering, Seoul National University of Technology, Seoul 139-743,
Korea
Abstract: A particle image velocimetry (PIV) technique has been used to
analyze the flow characteristics behind a road vehicle with/without an air
spoiler attached on its trunk and also to estimate its effect on the wake. A
vehicle model scaled in the ratio of 1/43 is set up in the mid-section of a
closed-loop water tunnel. The Reynolds number based on the vehicle length is
10^5. To investigate the three-dimensional structure of the recirculation zone
and vortices, measurements are carried out on the planes both parallel and
perpendicular to the free stream, respectively. The results show significantly
different vorticity distributions in the recirculation region according to the
existence of the air spoiler. The focus and the saddle point, appearing in the
wake, are disposed differently along the spanwise direction. Regarding the
streamwise vortices, the air spoiler produces large wing tip vortices. They
have opposite rotational directions to C-pillar vortices which are commonly
observed in the case that an air spoiler is absent. The wing tip vortices
generate the down force and as a result, they might make the vehicle more
stable in driving.
Keywords: PIV, road vehicle, Three-dimensional wake, Air spoiler, Isovorticity surface
