Ambient and induced pressure fluctuations in supersonic jet flows

An experimental investigation of the ambient static pressure fluctuations and induced acoustic fields in supersonic jet flows has been undertaken to identify possible noise sources and the mechanisms involved in the propagation of disturbances within the flows. The axisymmetric cold air jet under investigation exhausted from a 7-in. exit diameter C-D nozzle run in two conditions: one yielding a fully expanded flow and the other an overexpanded flow. The survey of static pressure fluctuations consisted of measurements of the overall levels and spectra of the fluctuations along the centerline of the two flows and the variation in level across various transverse sections. The second aspect of the study involved the development of a procedure for tracing the propagation of externally induced periodic pressure disturbances inside the jet.