Vortex breakdown in the near-wake of 25° Ahmed body

International audienceThe Ahmed body is an academic test-case meant to reproduce a wide range of the flow features encountered in automotive aerodynamics. The present work relies on high resolution Automated Stereo-PIV to clarify the structure and dynamics of the longitudinal vortices at high Reynolds number. The vortex core undergoes a sharp decay of streamwise velocity in the near wake which suggests possible occurrence of vortex breakdown. Confirmation comes from the sign switch of the azimuthal vorticity in the longitudinal plane intersecting the vortex core. The location of the sign switch seems strongly correlated to the modification of streamwise velocity