Microjet Influence on the Mixing of Supersonic Multi-Stream Jet Flow

Active flow control performed on a Multi-Aperture Rectangular Single Expansion Ramp Nozzle (MARS) using a series of microjets perpendicular to the flow. This campaign focused on determining how microjet configuration affects the instability at the interface of the core (M=1.6) and bypass (M=1) streams of the MARS jet. The microjets were located directly at the point of mixing between the two flows as previous simulations determined that point as the most effective at inducing mixing. Three characteristics of the microjets’ configuration were modified: the diameter of the microjets, the spacing of the microjets correlated to a known wave number based on previous passive control simulations, and the angle of the microjets relative to the flows. Actuation of the microjet flow was also be varied. Near field (affixed to the jet’s deck plate) and far field (downstream) pressure measurements taken in an anechoic chamber as well as time-resolved schlieren imaging were used to study the flow. Near field measurements studied the local unsteadiness at the nozzles exit, far field measurements were used to study the general directivity of the acoustic emissions, and time-resolved schlieren imaging was used to visually see how the active control manipulates the overall shock structure.