1995 Fiscal Year Final Research Report Summary
Study on Generation Mechanism of Aerodynamic Sound
| Project/Area Number |
05452304
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Aerospace engineering
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| Research Institution | Nagoya University |
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Principal Investigator |
NAKAMURA Yoshiaki Nagoya University, School of Engineering, Professor, 工学部, 教授 (80115609)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAZOE Hiromitsu Nagoya University, Center for Integrated Research in Science and Engineering, As, 理工科学総合研究センター, 助教授 (40260591)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Aerodynamic sound / Shear flow / Vortex / Axisymmetric jet / 渦 |
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| Research Abstract |
The objective of the present study is to elucidate the mechanism of aerodynamic sound generation by experimentally examining the relation betwneen the flow field and the sound field. The sound was made to generate by inserting a flat plate into the shear layr of axisymmetric jet. The results obtained are itemized as follows ; 1.The magnitude of generated sound is not related with the magnitude of flow fluctuation, but with the averaged value of spatial velocity gradient, that is, the strength of vorticity. When this value becomcs about 0.4, a large sound is generated from inside the shear layr. 2.The spatial distribution of velocity fluctuation inside the shear layr, specifically the normal component of velocity flnctuation has some relation with generated sound. The fluctuation is distributed in order around the plate edge when a large sound is generated. 3.The low speed jet has a distinguished sound with a frequency peak, while the high speed jet has flatly distributed frequenct spectrum. In addition to these results, we had developed a new method to predict the present sound by using the boundary element method. As a result, we found that the sound source is made when a vortex ring of the shear layr passes over the plate edge.
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