Transforming the Shock Pattern of Supersonic Jets Using Fluidic Injection

Double shock diamonds establish in the exhaust of modular convergent–divergent nozzles. These consist of two shock structures: one originating from the nozzle throat, and another from its exit. Analyzing the shock pattern developing for different fluidic injection operating conditions, it is shown that fluidic injection allows the rearrangement of the shock structures relative to each other. Overlapping the two structures causes large pressure oscillations in the exhaust and high amplitudes of shock associated noise, whereas staggering the shock structures mitigates these effects. The screech tone frequency does not change for all injection operating configurations, although the shock diamonds are shifted drastically with respect to each other. Hence, the screech phenomenon is dominated by the primary shock spacing originating from the nozzle throat.