Experimental Efforts On the Control of a Multi-Stream Supersonic Retangular Jet

Experiments are conducted on a supersonic Multi-Aperture Rectangular Single Expansion Ramp Nozzle with both passive and active flow control techniques. The baseline flow is comprised of two physical streams, a core (M = 1.6) and bypass (M = 1.0) stream that coalesce behind as plitter plate, merge, and exit through a rectangular orifice onto an aft-deck plate meant to mimic the nozzle being integrated into an air-frame. This interaction between the streams produces ahigh-frequency tonal phenomena that propagates throughout the flow-field. Passive control via age ometric modification to the splitter plates trailing edge (SPTE) is implemented to alleviate this tone. Active control is implemented via steady blowing through a span-wise array of micro-jets in the near-splitter plate region. A hybrid control case combining the active and passive methods is also investigated and compared to the baseline flow. All tests were conducted at the jets nominal perating conditions and measured via time-resolved schlieren images with synchronized far-field pressure measurements. Spectral Proper Orthogonal Decomposition (SPOD) of the schlieren data sets breaks down the spatio-temporal scales and reveals an eradication of the high-frequency tone in the cases with the modified (passive) SPTE. Active control with the nominal SPTE amplifies the tone and reduces it’s frequency, while simultaneously affecting the mean shock structures. The far-field acoustic measurements confirm these observations. Momentum potential theory based filtering is applied to the schlieren data-sets to isolate the acoustic phenomena ejecting from the nozzle exit. The filtered data-sets are then analysed via SPOD and reveal a shift in the spectra between the different control cases with the first shock-shear layer interaction location acting as a source for noise generation in all cases.