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Background noise measurements from jet exit vanes designed to reduced flow pulsations in an open-jet wind tunnelMany open jet wind tunnels experience pulsations of the flow which are typically characterized by periodic low frequency velocity and pressure variations. One method of reducing these fluctuations is to install vanes around the perimeter of the jet exit to protrude into the flow. Although these vanes were shown to be effective in reducing the fluctuation content, they can also increase the test section background noise level. The results of an experimental acoustic program in the Langley 4- by 7-Meter Tunnel is presented which evaluates the effect on tunnel background noise of such modifications to the jet exit nozzle. Noise levels for the baseline tunnel configuration are compared with those for three jet exit nozzle modifications, including an enhanced noise reduction configuration that minimizes the effect of the vanes on the background noise. Although the noise levels for this modified vane configuration were comparable to baseline tunnel background noise levels in this facility, installation of these modified vanes in an acoustic tunnel may be of concern because the noise levels for the vanes could be well above background noise levels in a quiet facility.
Document ID
19850019604
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Hoad, D. R.
(Army Research and Technology Labs. Hampton, Va., United States)
Martin, R. M.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 5, 2013
Publication Date
June 1, 1985
Subject Category
Research And Support Facilities (Air)
Report/Patent Number
AD-A157114
AVSCOM-TM-85-B-1
NASA-TM-86383
L-15923
NAS 1.15:86383
Accession Number
85N27916
Funding Number(s)
PROJECT: DA PROJ. 1L1-63309-AH-76
PROJECT: RTOP 505-42-23-09
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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