Abstract
An actuator to control hairpin vortex was made and tested in a water channel, which generates a circulation opposite to those by the hairpin vortices. Velocity fluctuation measurements by hot-film in the boundary layer show the decreasing of u-disturbance. Actuation may control the hairpin vortices -reduction of the magnitude of vorticity. The decreasing of the vortices of ω_x is due to opposite tilting (ω_2∂u/∂z<0), ω_y and ω_z are weakened by vortex compressing (ω_y∂v/∂y<0,ω_2∂w/∂z<0).
