On Investigating the Hydrodynamic Field for Jets with and without Installation Effects

Near-field hydrodynamic and acoustic characteristics of an unheated subsonic jet with chevron nozzles were investigated experimentally with and without jet installation effects. Near-field pressure fluctuations were acquired for Mach numbers ranging from 0.3 to 0.9 for four different types of chevron nozzles in an anechoic jet facility at the University of Bristol. The measurements were carried out on an axial microphone array traversed in the radial direction and placed close to the jet. The tests were performed for several plate heights from the nozzle to investigate the effect of plate distance from the jet. The results are presented for sound pressure level and overall sound pressure level for several radial locations. Further analyses were carried out by decomposing the near-fieldpressure into hydrodynamic and acoustic components. The investigation clearly shows the effect ofjet installation on the hydrodynamic and acoustic fields. Auto-correlation and cross-correlation analysis was also carried out for the near-field pressure fluctuations. The convective velocity of the flow isreduced by the use of chevrons. The use of chevron nozzles changes the acoustic pressure in the nearfield region thereby shifting the dominant noise source towards the nozzle exit for both the installedand isolated configurations.