A number of jet noise experiments have been performed over the years in different facilities and measured lossless spectra do not always match. Some researchers suggested this discrepancy is associated with rig noise. Another school thought that could be due to differing nozzle-exit boundary layers. One criticized datasets Tanna database, which was acquired at Lockheed Georgia anechoic jetfacility, now operated by Tech Research Institute (GTRI), where current authors work. In paper,...

Often the measurements from different jet noise studies, which are thought to have been acquired at or corrected identical conditions, do not match when compared each other. This study looks nozzle-exit boundary layer as a possible factor for these differences. The state can easily be changed depending on design of jet-facility nozzle. To this end, and velocity profile were nozzles where was either by using types nozzles, ASME versus conical extensions added straight section. It is shown...

Often, lossless jet-noise data obtained by various researchers in different facilities do not match after accounting for jet operating conditions, measurement distance, and nozzle dimensions using accepted scaling laws. There have been a number of explanations these differences, but the most contentious is attributing rig-noise contamination to be cause differences. This reasoning calls all measurements that acquired facility into question. Knowing if noise contaminated rig given crucial...

Model-scale jet-noise experiments using a dual-stream, axisymmetric confluent nozzle with an area ratio of about 0.62 were conducted. Farfield acoustic measurements acquired extraction (the bypass stream's total pressure divided by the core pressure) unity and above are discussed – both in terms spectral noise characteristics OASPL directivity. A mixing-length dependence farfield is measured streams unheated operating at same revealing subtle high-frequency reduction increased mixing length...

Model-scale experiments conducted with an axisymmetric, dual-stream confluent nozzle area ratio of 0.62 reveal that the produces a self-excited flow at certain operating conditions. This work aims to characterize which arises high-subcritical pressure ratios unity extraction (the bypass flow's total core flow). In addition loud tones, there is broadband amplification jet noise measured in farfield. Ensemble-averaged PIV measurements significant shortening jet's potential and concentrated...

Most university researchers typically end up using small nozzles to study jet noise. The data acquired from many of such existing studies has been used develop noise prediction schemes. However, it is not quite clear as how the nozzle can be before becomes unreliable. There are two-fold issues here: (1) may difficult obtain similarity in upstream boundary layer characteristics well flow development plume for smaller nozzles; and (2) fixed exit velocities Reynolds numbers smallscale provide...

An experimental facility was recently developed at the Georgia Tech Research Institute to measure acoustic scattering coefficients of a test article under mean flow, high-temperature, high-amplitude, and higher-order mode propagation conditions. The acts like two-sided impedance tube, in which measurement section is circular duct with 16 drivers microphones mounted on each side article. Such can be configured for grazing bias flow measurements liners sound traveling against direction flow....

The Reynolds number and Mach are classical quantities used to determine the similarity of aerodynamic flows. Existing studies on role Number jet noise show inconsistent results, casting doubt how small a nozzle diameter can be for scaling laws hold. A systematic study was therefore undertaken resolve this issue. flows adjusted using variation between 0.4 0.8, nozzle-exit diameters 0.25, 0.5, two inches. When measurements were normalized, spectral collapse observed spectra across whole range....

Imperfectly expanded supersonic jets contain a shock-cell structure in the jet plume which plays role generating screech tones along with other noise sources. Depending on Mach number of jet, two types motion or “jet modes”—a toroidal mode and flapping may occur, resulting generation different that are not harmonics each other. At given condition, these modes (and corresponding tones) can switch between based environmental conditions seemingly non-deterministic manner. Understanding when...