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

C. Jermann (1, 2) , G. Pujals (1) , Philippe Meliga (2) , E. Serre (2) , F. Gallaire (3)

1 PSA - PSA Peugeot - Citroën
2 M2P2 - Laboratoire de Mécanique, Modélisation et Procédés Propres
3 Laboratory of Fluid Mechanics and Instabilities

The 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.

Mots clés: Vortex Breakdown; Stereo-PIV; Ahmed body; Longitudinal vortices

Domaines: Mécanique des fluides [physics.class-ph]

C. Jermann, G. Pujals, Philippe Meliga, E. Serre, F. Gallaire. Vortex breakdown in the near-wake of 25° Ahmed body. 10th EUROMECH European Fluid Mechanics Conference, Sep 2014, Copenhague, Denmark. ⟨hal-01309904⟩