Active Control of Coherent Structures in a Supersonic Rectangular Jet

The effects of excitation on the coherent structures in a supersonic rectangular jet with a design Mach number of [Formula: see text] are investigated. Planar laser-sheet imaging and time-resolved schlieren imaging, combined with spectral proper orthogonal decomposition (SPOD), are used to investigate the jet over three flow regimes. Coherent structures within the jet shear layers are clearly visualized and are shown to dominate the first SPOD mode at both the natural screech frequency and the excitation frequency. The robust response of the jet is over a large range of frequencies consistent with the overlap between the jet column mode and the shear layer mode. Excitation at frequencies higher than the weak screech frequency of the design condition disrupts the naturally occurring coherent structures. Furthermore, excitation of different azimuthal modes alters both the organization and energy content of these structures within the jet. In the presence of screech staging, excitation can also change the dominant tonal peak within the jet. Excitation also changes the overall entrainment and mixing characteristics of the jet.