Active Control of an Axisymmetric Jet Using Moving Delta-tabs

1st Report, Measurements of a Jet with Delta-tabs Moving in Phase

Abstract

In an attempt to control an axisymmetric jet using multiple “moving delta-tabs” having triangular shapes, an experimental investigation was performed. Computer-controlled five delta-tabs, which can be driven independently, were installed at the skimmer. Two modes were tested : in the first case, all delta-tabs were stationary (i.e. conventional way) and in the second case, delta-tabs were oscillated in phase at the frequency of 4 Hz. A rake of 21 I-type hot wires was used to measure instantaneous velocities. The results were compared with a canonical axisymmetric jet without tabs. The results show that turbulence quantities such as mean and rms velocities, skewness, kurtosis, probability density function, power spectra are significantly altered by the stationary and moving delta-tabs. The effects of the oscillation of the delta-tabs were found to modify the large-scale structures in the near field of the jet. The results suggest the active control of an axisymmetric jet using moving delta-tabs.