Turbulent Round Jet Control Using Two Steady Minijets

The mixing performance of a turbulent jet is controlled using two steady side radial minijets, improving our understanding of the underlying physics behind the enhanced mixing performance. The jet apparatus consisted of a diffuser, a cylindrical settling chamber of 114 mm in diameter, and a smooth contraction nozzle with a diameter of 20 mm. The spectra presented in this work are an average of at least 34 sets of data, implying a resolution considerably better than 0.9 Hz or an experimental uncertainty of less than 1% in the estimate of St. In the (x, y) plane, the minijet injection upstream of the jet exit may destroy the well-defined shear layer, thus preventing the generation of azimuthal ring vortices. The minijet injection produces a predominant quasiperiodic coherent structure in the flow before its issue from the nozzle exit.