Effects of high frequency blowing perturbation on a turbulent boundary layer

An experimental study is conducted on a zero pressure gradient flat plate for investigating the effects of a periodical perturbation on the turbulent boundary layer over the flat plate. This experiment is focused on studying the effects of high frequency blowing on statistical characteristicss of near wall turbulence. By measuring and analyzing streamwise velocity signals at different streamwise locations with and without a periodical perturbation induced by a synthetic jet actuator, the conclusion of the experiment indicates skin friction reduction can be achieved downstream of the slot by applying high frequency periodical blowing perturbation. Owing to the intensity of the perturbation in the turbulent boundary layer is attenuating along the streamwise, the interaction between the perturbation and turbulent flow structures is attenuating. However, the negative spanwise vortexes induced by the high frequency perturbation are nearly of the same scale as the structures of bursting events, which directly impact the statistics of production and evolution of near wall coherent structures. As a result, the outcomes of bursting detection methods like VITA in the experiment show a contradictory phenomenon to the mechanism of skin friction reduction in low frequency blowing or steady blowing.