| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
This research has been carried out by the author of this report with the assistance of graduate and undergraduate students as well as a post doctorial student..
1. Designing and construction of a vertical wind tunnel: We made a vertical wind tunnel that can generate a vertical jet. Measurement of thrust loss of noise suppressors was easily carried out by using the wind-tunnel. Special attention was paid to the avoidance of pressure drop at the flange of the exit.
2. Measurement of thrust: Comparison between thrusts of flows issued from a nozzle with and without a reflector. It was found that the attachment of a reflector reduces a thrust only a little bit. Measurements of thrust loss of perforated tubes were also carried out. The attachment of a perforated tube also reduced the thrust. The amount of the loss, however, decreased as jet pressure ratio increased. Theoretically a perforated tube can increase a thrust at a high pressure ratio.
3. Measurement of acoustic power: Change in acoustic power by the attachment of a spherical reflector has measured in a reverberant room in a pressure-ratio-range of 2.0 to 6.0. Measurements of acoustic power of various perforated tubes were also performed.
4. Evaluation of General Performance of Advanced Noise Suppressors: Slotted tubes suffered from smaller thrust loss compared to perforated tubes. The performance of noise reduction of slotted tubes was inferior to perorated tubes. From overall view point, a tube with forward slanted perforation with a porosity of 0.03 (practical value) showed best performance among all tested tubes.
5. Presentation and publishment :The results of the present research have been presented at 7th ISAIF (Tokyo, 2005), 12th ICSV (Lisbon, 2005), 13th ICSV(2006,Vienna), ASA/AS Joint meeting (Honolulu, 2006), internoise 2006 (Honolulu, 2006) and at another 4 international conference and 19 papers have been published.
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