Fluidic injectors for supersonic jet control

An experimental investigation on the mixing capability of a Mach 2.0 jet manipulated based on a convergent injector (CI) and convergent-divergent injector (CDI) is reported in this paper. The injector parameters that influence the core length of the manipulated jet (Lc), such as the mass flow rate ratio C_m of the minijets to the main jet and the expansion ratio p_e/p_a (where p_e and p_a are the nozzle exit and atmospheric pressures, respectively), are examined in detail. The experimental diagnostics include the detailed Pitot pressure measurement along the jet centerline and the shadowgraph visualizations captured in the orthogonal planes of the manipulated jet. Various flow structures have been identified based on the shadowgraph visualization, such as categories I and II corresponding to the off-design and design conditions of the primary jet, respectively. The core length of the manipulated jet exhibits a strong dependence on C_m, p_e/p_a, and the type of injection (CI or CDI). The jet mixing quantified based on ΔLc∗ (where ΔLc∗ is the percentage reduction in core length of the manipulated jet with respect to the natural jet) is maximum at the design condition than the off-design condition implying that the jet manipulation is highly efficient at the design condition.