SHEAR LAYER REFRACTION CORRECTIONS FOR OFF-AXIS SOURCES IN A JET FLOW
✍ Scribed by C.L. MORFEY; P.F. JOSEPH
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 343 KB
- Volume
- 239
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
A set of equations is derived for converting acoustic measurements taken in a free-jet #ight simulation facility, such as the U.K. Noise Test Facility at Pyestock or the French CEPRA-19 wind tunnel at Saclay, to equivalent far"eld #ight conditions. The equations are based on the high-frequency geometrical acoustics approximation, whose application in the present context was justi"ed in early studies by Morfey and Tester in 1977 and by Amiet in 1978. However, the present work di!ers by allowing the source to be positioned o! the jet centreline, anywhere within the #ight stream. The #ight stream jet is modelled as an axisymmetric parallel shear #ow, with a shear layer thickness which is small compared with the jet diameter. The model also permits the microphone to be located anywhere outside the #ow, arbitrarily close to the open jet. The consequences of o!-axis source location are illustrated by numerical calculations.