Investigation of the Ahmed body cross-wind flow topology by robotic volumetric PIV

Abstract

Robotic volumetric PIV is employed to investigate the time-averaged three-dimensional near-wake flow topology of the Ahmed body in steady cross-wind conditions. The model selected for this study is a 1:2 replica of the reference Ahmed body with 25° slant angle. The measurements are conducted at free-stream velocity of 12 m/s, resulting in a Reynolds number of 1.15×105 based on the model’s height. Yaw angles of 0°, 4° and 8° are considered. The results show that the position and strength of the C-pillar vortices are significantly influenced by the presence of a yaw angle. The yaw angles cause an increase in the strength of the windward C-pillar vortex, with a consequent upward displacement; conversely, the strength of the leeward vortex decreases, and the position of its core moves downwards and inboard. At the larger yaw angle, the presence of a ground streamwise vortex is detected which co-rotates with the windward C-pillar vortex and is located between the latter and the ground.