Active Control of Acoustics in a Supersonic Circular Jet

The acoustics of a supersonic circular jet were studied using active flow control over a limited frequency band. The nozzle was designed using the Method of Characteristics with a design Mach number of 1.52 and an exit diameter of 1 inch. The results presented in this paper were obtained at the Gas and Dynamics Laboratory at the Ohio State University. The baseline acoustics were analyzed for two flow regimes, overexpanded and ideally expanded, and a variety of excitation parameters, varying frequency and azimuthal mode, were applied to investigate the jet’s response. For the ideally expanded case it was found that when exciting at a frequency within the jet column mode (JCM), the jet responded for all azimuthal modes investigated (m = 0 , 1 , 3. 1), but with the strongest response occurring at the jet’s natural azimuthal mode (m = 1). For the weakly screeching overexpanded case, when exciting at screech frequency, the screech is reinforced when exciting at the jet’s natural mode and is disrupted when other modes were used. For both cases, when exciting at a frequency higher than the JCM, a weak response was produced for the ideally expanded case, with minimal variations between excitation modes. However, for the overexpanded case, the control was able to further disrupt the screech, with a larger impact when exciting at the jet’s nondominant azimuthal modes.