Jet noise reduction using pulsed fluidic actuation

Abstract

© 2011 International Symposium on Turbulence and Shear Flow Phenomena, TSFP07. All rights reserved.Steady and unsteady fluidic actuators, in the form of secondary control jets injecting from the nozzle lip, aimed at jet noise reduction, are investigated. Three different geometric configurations are tested: non-converging control jets, 'open' triangle convergence and 'closed' triangle convergence. By means of a triple decomposition of hot-wire data and a scale-separation argument, the low-frequency perturbation (near-nozzle dynamics) and response (global, downstream dynamics) of the flow are studied. Comparison of the phase-averaged component of the decomposition with predictions of linear stability theory (LST) suggest that two qualitatively different responses are active: at the main forcing frequency the jet response looks to be non-linear; at two secondary, higher frequencies, LST gives reasonable predictions for the local growth rates and convection velocities.