Empirical scaling analysis of jet control using unsteady minijet

Abstract

This work presents the active control of a turbulent axisymmetric jet using single unsteady minijet. The forcing parameters include the ratio fe/fo of the minijet excitation frequency fe to the main jet preferred-mode frequency fo, duty cycle (α) the fraction of time the minijet is “on” during each pulsation cycle, the mass flow rate ratio Cm of the minijet to the main jet, and the exit diameter ratio d/D of the minijet to main jet. The jet centerline velocity decay rate K is used to evaluate jet entrainment rate, given by an equation of K = (Ūe – Ū5D)/Ūe, where Ue and U5D denote the jet centerline mean velocities at x* = x/D = 0 and 5, respectively. Extensive hotwire measurements were performed in the injection, orthogonal non-injection planes of the perturbed jets. © 2018 Australasian Fluid Mechanics Society. All rights reserved.