The NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel is a premier facility for model-scale testing of jet noise reduction concepts at realistic flow conditions. However, flow inside the open jet test section is less than optimum. A Construction of Facilities project, scheduled for FY 05, will replace the flow collector with a new design intended to reduce recirculation in the open jet test section. The reduction of recirculation will reduce background noise levels measured by a microphone array impinged by the recirculation flow and will improve flow characteristics in the open jet tunnel flow. In order to assess the degree to which this modification is successful, background noise levels and tunnel flow are documented, in order to establish a baseline, in this report.Booth, Earl R., Jr. and Henderson, Brenda S.Langley Research CenterAEROACOUSTICS; LOW SPEED WIND TUNNELS; WIND TUNNEL TESTS; JET AIRCRAFT NOISE; NASA PROGRAMS; BACKGROUND NOISE; TEST FACILITIES; NOISE INTENSITY; NOISE REDUCTION; FLOW CHARACTERISTICS; MICROPHONES; DATA PROCESSING; ACOUSTIC MEASUREMENT; JET FLOW

The NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel is a premier facility for model-scale testing of jet noise reduction concepts at realistic flow conditions. However, flow inside the open jet test section is less than optimum. A Construction of Facilities project, scheduled for FY 05, will replace the flow collector with a new design intended to reduce recirculation in the open jet test section. The reduction of recirculation will reduce background noise levels measured by a microphone array impinged by the recirculation flow and will improve flow characteristics in the open jet tunnel flow. In order to assess the degree to which this modification is successful, background noise levels and tunnel flow are documented, in order to establish a baseline, in this report.

Tests were performed on a 1/20th-scale model of the Low Speed Aeroacoustic Wind Tunnel to determine the performance effects of insertion of acoustic baffles in the tunnel inlet, replacement of the existing collector with a new collector design in the open jet test section, and addition of flow splitters to the acoustic baffle section downstream of the test section. As expected, the inlet baffles caused a reduction in facility performance. About half of the performance loss was recovered by addition the flow splitters to the downstream baffles. All collectors tested reduced facility performance. However, test chamber recirculation flow was reduced by the new collector designs and shielding of some of the microphones was reduced owing to the smaller size of the new collector. Overall performance loss in the facility is expected to be a 5 percent top flow speed reduction, but the facility will meet OSHA limits for external noise levels and recirculation in the test section will be reduced. Booth, Earl R., Jr. and Coston, Calvin W., Jr. Langley Research Center NASA/TM-2005-213534, L-19093

Tests were performed on a 1/20th-scale model of the Low Speed Aeroacoustic Wind Tunnel to determine the performance effects of insertion of acoustic baffles in the tunnel inlet, replacement of the existing collector with a new collector design in the open jet test section, and addition of flow splitters to the acoustic baffle section downstream of the test section. As expected, the inlet baffles caused a reduction in facility performance. About half of the performance loss was recovered by addition the flow splitters to the downstream baffles. All collectors tested reduced facility performance. However, test chamber recirculation flow was reduced by the new collector designs and shielding of some of the microphones was reduced owing to the smaller size of the new collector. Overall performance loss in the facility is expected to be a 5 percent top flow speed reduction, but the facility will meet OSHA limits for external noise levels and recirculation in the test section will be reduced.

Wind Tunnel Test Techniques: Design and Use at Low and High Speeds with Statistical Engineering Applications provides an up-to-date treatment of the topic. Beginning with a brief history of wind tunnels and its types and uses, the book goes on to cover subsonic, supersonic and hypersonic wind tunnel design and construction, calibration, boundary corrections, flow quality assessment, pressure surveys, and dynamic testing. It also focuses on wind tunnel facilities, making it useful for both the designer and operator. Engineers and graduate students in aerospace, automotive and similar programs will find this book useful in their work with experimental aerodynamics, gas dynamics, facility design and performance. Deals with a broad range of flow speeds in wind tunnels, from low speed to high speed Provides a discussion of similarity laws as well as material on statistical analysis Includes coverage on facility-to-facility and facility-to-CFD correlation Presents advanced topics such as cryogenic wind tunnels, ground simulation in automotive testing, and propulsion testing