Abstract:
Experimental investigation is conducted in a wind tunnel to study the influence of spanwise-inclined wall jets on the coherent structures in a turbulent boundary layer. The instantaneous velocity signals are captured by hot-wire anemometry. Comparison of velocity statistics in the turbulent boundary layers (TBLs) with and without control reveals that the wall jets significantly reduce the mean streamwise velocity. Furthermore, the velocity fluctuation in the near-wall region is suppressed while enhanced farther away from the wall. Wavelet analysis results show that the most energetic scale in both the uncontrolled and controlled flows appears at the 9th scale, which corresponds to a spatial length of approximately 950 viscous units based on Taylor’s frozen hypothesis. Conditionally averaged profiles, based on the reconstructed signals from the most energetic scale, demonstrate that the inclined wall jets effectively modulate the sweep and ejection events, lifting the turbulent structures away from the wall and thereby weakening the turbulent activities in the near-wall region while intensifying them in the outer region.