Subsonic Jet Mixing via Active Control Using Steady and Pulsed Control Jets

Abstract

A comparison of the performance of steady and pulsed control jets in enhancing the mixing rate of a high Reynolds number (10 6 ) high subsonic Mach number (0.9) jet is reported. The key parameters affecting control jet performance are identified as control jet pressure ratio, Strouhal number (St), and mode number (m), and an existing nozzle test facility is modified to allow detailed investigation of these parameters. Optimization of the control jet design lead to increased mixing, such that a primary jet potential core length reduction of 50% was achieved. The increase in jet/ ambient entrainment interfacial area was seen as an important factor. Pulsation at St = 0.22 in an antisymmetric mode (m = 1) gave the best results. The data provided, based on extensive laser Doppler anemometry mean velocity and turbulence measurements, allowed an improved understanding of the physical processes that are crucial for enhanced mixing and contribute a useful new data set for computational fluid dynamics validation of rapid mixing jet flows.