2001 Fiscal Year Final Research Report Summary
Study of the Structure of Wall-Turbulence and Turbulence Noise
| Project/Area Number |
11305018
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Osaka University |
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Principal Investigator |
MIYAKE Yutaka Dept. Mech. Eng.,Osaka University, Professor, 大学院・工学研究科, 教授 (50029005)
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| Co-Investigator(Kenkyū-buntansha) |
OHTA Takashi Dept. Mech. Eng.,Osaka University, Research Associate, 大学院・工学研究科, 助手 (10273583)
TSUJIMOTO Koichi Dept. Mech. Eng.,Osaka University, Research Associate, 大学院・工学研究科, 助手 (10243180)
KAJISHIMA Takeo Dept. Mech. Eng.,Osaka University, Associate Professor, 大学院・工学研究科, 助教授 (30185772)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Wall Turbulence / Vortical System / Streaks / Turbulence Noise / Rough Wall / Noise Propagation / Aeroacoustics / CAA |
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| Research Abstract |
Several subjects are in concern in this research program. Namely, interaction between near-wall layer up to several tens in wall unit and outer layer, modulation of outer layer which may contribute to drag reduction and turbulence noise emitted from wall turbulence.
As for the interaction problem, model simulations under certain artificial conditions revealed that near-wall layer over smooth wall has remarkable self-sustenance ability and universality, independent on the property of outer layer. Roughness on the wall has been found to destruct this property and makes almost whole layer occupied by the property of outer layer. Channel flow having wavy wall has confirmed the conclusion.
Outer layer property modulated by solid particles has been investigated as well. New technique invented to trace particles in motion works satisfactorily and revealed important aspects of turbulence dynamics that may be applicable for turbulence control.
Noise emitted from turbulence over a wall has been simulated without using any models. Source field and accompanying acoustic field have been consecutively calculated in time-marching manner. It turned out that not all the vortices generate sound but certain particular events of vortex only contribute for noise generation. As the basis of enhancing reliability of noise calculation, free round jet has been simulated with high resolution. Near field of a jet which is most responsible for noise generation has been also investigated with respect to the mechanism of birth of vortical structure, by global stability analysis.
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