Abstract
Control of near-wall large-scale vortices is significant for a skin frication reduction in the turbulent boundary layers. From this viewpoint, the mechanism to control hairpin vortices in the transitional boundary layers developing on a flat plate is studied. Using a pair of wings, which is designed so that each wing generates a circulation opposite to longitudinal hairpin vorticity, hairpin vortices have been manipulated. This configuration of the wings results in as much as 35% turbulent fluctuation reduction. This technique will be applied to manipulation of many hairpin vortices generated by acoustic excitation with a loudspeaker.
