Influence of a synthetic jet excitation on the development of a turbulent mixing layer

This paper concerns the experimental study of the control of a turbulent plane mixing layer by a single array of synthetic (loudspeakers) jets deployed through circular orifices. The displacement of the mixing layer towards the wall partially mimics the flow control scenario of the reattachment of a massively separated flow with the jets positioned after the separation location. The experimental setup is the mixing layer downstream of a splitter plate positioned at a small distance away from a flat plate. PIV observations show that the synthetic jet abruptly destroys the large scale coherent structures. There is a large modification to the turbulence field due to the distortion in the mean velocity field. An overall increase in the mixing of the flow between the flat plate and the mixing layer which cause the deviation of the flow towards the wall surface. Lastly, a parametric study of the synthetic jet trajectory is realized by varying the velocity of the air stream that generates the mixing layer. The ratio of the peak jet velocity to the lower velocity of the mixing layer should not be overly excessive such that the jet penetrates the mixing layer completely.