Effects of synthetic jet parameters on turbulent boundary layer

The motion of coherent structures such as hairpin vortices is the main factor leading to the complex flow state in the turbulent boundary layer, and the study of their developmental and evolutionary laws contributes to the understanding and control of turbulence. Time-resolved particle image velocimetry (TRPIV) is used to study the effects of synthetic jet parameters on the turbulent boundary layer. By comparing the mean velocity and turbulence intensity under various control parameters, it is found that the synthetic jet leads to a velocity deficit in the boundary layer. Calculating the vortex field and analyzing it using the phase averaging method, it is found that the synthetic jet periodically generates vortex structures downstream of the slot. The vortex strength and vortex structure development height are positively correlated with the input voltage and negatively correlated with the excitation frequency. The conditional averaging method is applied to calculate the burst event strength and spatial form, and it is concluded that the synthetic jet can enhance the sweeping effect of high-velocity fluid but reduce its spatial scale. The two-point correlation function is used to extract the coherent structure, and the spatial scale of coherent structures is defined by the ellipse fitting method. The results show that the synthetic jet can effectively reduce the streamwise and wall-normal scales of hairpin vortex packages, and make the vortex packages move away from the wall due to the lifting effect of the synthetic jet on the vortex structure.