Characterization and control of longitudinal vortices over a dihedral bluff body : numerical approach
Résumé
A longitudinal vortex emanating from the front pillar of a simplified dihedral geometry is analysed by numerical simulations. The objective is to develop and validate flow control techniques able to act on the dynamics of such vortices in order to reduce aerodynamic drag of automotive vehicle. Numerical simulations are conducted according to a computation code based on the Lattice Boltzmann method. The findings highlight the sudden and spontaneous disintegration of the vortex referred to vortex breakdown, which is characterized by the appearance of a recirculation zone in the vortex core. Open loop control is then applied by continuous blowing or suction on the edge of the front pillars. The results reveal that suction-type control tends to delay the breakdown of the vortex while blowing-type control triggers the onset of vortex breakdown upstream compared to the uncontrolled case. Aerodynamic drag reductions of close to 40% are obtained with suction-type control.