摘要: The acoustic near-field of a supersonic underexpanded jet at M_j=1.34 was studied experimentally. A near-field azimuthal microphone array was utilized to study the jet oscillation dynamics and infer the geometrical pattern of the ... 展开 The acoustic near-field of a supersonic underexpanded jet at M_j=1.34 was studied experimentally. A near-field azimuthal microphone array was utilized to study the jet oscillation dynamics and infer the geometrical pattern of the upstream-traveling acoustic waves involved in the jet screech mechanism. Operation of the jet in isolation resulted in a lateral oscillation (mode B) with an acoustic field containing strong screech tones. Addition of a conical reflector of 60° cone half-angle changed the oscillation dynamics, with new mode E appearing prominently and coexisting with mode B. The cross-spectral densities at the distinct tone frequencies are utilized to discern the jet oscillation dynamics and screech frequency and wavelength prediction formulas are utilized to assess if mode E is an extension of previously observed screech modes. 收起