| Project/Area Number |
10450373
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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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, 工学研究科, 教授 (80115609)
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| Co-Investigator(Kenkyū-buntansha) |
MENSHOV Igor Nagoya University, School of Engineering, Lecturer, 工学研究科, 講師 (70262871)
NAKANISHI Tameo Yamagata University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (10235799)
KAWAZOE Hiromitsu Tottori University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (40260591)
エブネディン ハミディ・ヘサメディン (エブネディン・ハミディ) 名古屋大学, 工学研究科, 助手 (30303671)
濱本 直樹 名古屋大学, 工学研究科, 日本学術振興会特別研
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥12,400,000 (Direct Cost: ¥12,400,000)
Fiscal Year 2000: ¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1999: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1998: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Keywords | jet / noise / mixing / instability / screech / shear layer / transition / supersonic flow / 空力音 / ジェットノイズ / 渦 / マッハ波 / 自由せん断層 / 音波 |
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| Research Abstract |
In this study both numerical simulation and experiments regarding high-speed jets were performed. In the experiments mini-jets were used as an actuator to enhance jet mixing, the results of which are summarized as follows : (1) The flapping mode of actuation was most effective in mixing, where the axial length of the potential core was reduced by 35%, compared with that of the baseline. (2) As the frequency of actuation becomes higher, the jet breaks down more upstream. (3) As under-expanded jets are intrinsically stable, it does not change so easily by external disturbances, compared with the case of optimum jet. (4) As for noise, only steady actuation can decrease the noise level. On the other hand, regarding numerical simulations, the following results were obtained. (1) In axisymmetric calculation of jet, periodical roll-up of the jet shear layer was observed. These vortices merge with each other, and show the motion of acceleration, which leads to sound emission. (2) In 3D simulation, some instability produced upstream cannot maintain the state of being axisymmetric in the downstream, and three-dimensional unstable modes appear. As a result, the degree of jet breakdown is weakened, which reduces Mach wave-like sound emissions. (3) The velocity distribution along the jet axis shows good agreement between 3D numerical simulation and experimental data. However, there is a slight difference between them in the downstream. (4) In under-expanded jets, vortices in the jet shear layer interact with the shock cell, which makes a kind of noise.
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