Perturbing shear layers in a turbulent wake
Résumé
The impact of shear layer forcing on the recirculating flow past a turbulent bluff body wake is examined.
Flow disturbances generated using active and passive devices modify the evolution of the separated flow from the
rear edges of a rectangular geometry. A system of pulsed
jets with variable frequency allows us to produce unsteady
perturbations, whilst passive boundary layer forcing is obtained by spanwise cylinders with variable diameter. Statistics of velocity fields obtained from particle image velocimetry (PIV) are used to quantify the changes in the recirculating flow. Depending on the forcing frequency or
perturbation size, the wake balance is modified due to the
enhanced mixing along the forced shear flow. The experimental results show that the symmetry properties of the
near wake can be controlled by suitable excitation and provide guidelines for the control of wake-related aerodynamic
forces exerted on bluff bodies.