Commissioning and Validation of a New Jet Rig for the QinetiQ Noise Test Facility

Jet Noise Measurements: Past and Present

“…The results confirm that normal to the jet, the dependence at constant Strouhal number follows eight powers of jet velocity across the whole of the velocity and frequency range investigated. This adds further confirmation of the absence of any significant rig noise in these measurements, which is known to vary as the fourth power of the velocity [22]. At other angles, convective amplification of about two or three powers of the Doppler factor is evident, except at high frequencies close to the jet axis where refraction is present and the dependence returns to eight powers.…”

“…Originally limited to 1/25 th scale in flight simulation mode, the NTF's air systems have recently been upgraded to handle 1/10 th scale models of modern high BPR turbofan exhausts including provision of a 1.8m diameter flight stream nozzle ( [21], [22]). These timely improvements permit study of the full acoustic spectrum under representative take-off and approach conditions, while making inclusion of fine engineering details (e.g.…”

“…It is reasonable to suppose an even larger margin for the higher velocities of figure 6. The procedure adopted here of employing a larger nozzle for the measurement of rig noise, is a standard one used today for example in the NTF [22], LSAF [14] and SHJAR [23]. Hence, unless something had come adrift within the rig, it seems highly unlikely that the additional peak noise in the TANNA data is contamination by rig noise.…”

Effect of Initial Condition on Subsonic Jet Noise from Two Rectangular Nozzles

“…It was noted that data taken in cleaner "University-type" facilities [3][4][5][6] were actually noisier relative to data taken in "Industrialtype" facilities [1,7,8]. In [9] another pertinent observation was made; two round nozzles of same exit diameter but different internal geometry ("ASME" versus "Conic"), tested in the same facility, displayed a significant difference in the noise spectra.…”

Investigation of Flow Conditioners for Compact Jet Engine Simulator Rig Noise Reduction

“…This excess noise due to the high speed jet flow issuing through the flow conditioner is referred to as "self-noise" in the current work and must also be considered. There have been several valuable studies, such as Brown and Bridges 5 and Harper-Bourne 6 , that systematically document the identification and mitigation of jet rig noise during the course of facility validations. Recent work by Brown, et al 7 also discusses rig noise due to a reticulated foam metal flow conditioner as part of a larger study on acoustic data quality.…”