Controlling the Instability at the Interface of Supersonic Streams Within a Modern Rectangular Jet Nozzle*

Modern jet nozzle designs for next-generation aircraft often exhibit distinct features such as multiple flow streams or non-axisymmetric exits. This study expands upon extensive experimental and computational research on a Multi Aperture Rectangular Single Expansion Ramp Nozzle, characterized by core (M=1.6) and bypass (M=1.0) streams that merge behind a splitter plate and exit onto an aft deck meant to simulate air frame integration. Preliminary research has determined that the region where the two streams meet produces an unwanted tone ubiquitous within the flowfield. To mitigate this tone that results from the complex shedding instability, flow control techniques are applied experimentally. A spanwise wavenumber is introduced to the splitter plates trailing edge (SPTE) as a means to passively affect the mixing in the shear layer. Additionally an array of microjets are introduced just below the SPTE region and actuated to provide a more tuned active control approach to affecting the instability. Experiments are performed within an anechoic chamber utilizing simultaneous near and far-field pressure measurements as well as schlieren imaging to quantify the efficacy of the control methods and observe changes to the spectral characteristics as well as shock behavior of the system.