| Project/Area Number |
17540349
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Mathematical physics/Fundamental condensed matter physics
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| Research Institution | University of Tokyo |
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Principal Investigator |
YOKOI Nobumitsu University of Tokyo, Institute of Industrial Science, Research Associate, 生産技術研究所, 助手 (50272513)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | turbulence / swirling flow / helicity / variational analysis / transport suppression / turbulence model / data analysis / numerical simulation |
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| Research Abstract |
A variational analysis based on the notion of the helicity (correlation between the velocity and the vorticity) was performed. It was shown that the mean-velocity profiles that minimize the enstrophy of the mean flow under the constraint of the constant helicity is realized, whose profiles are in good agreement with the counterpart observed in a turbulent swirling flow. In addition to the helicity constraint, we took the angular-momentum conservation into consideration. This treatment made it possible to reproduce the mean-velocity profiles in an axially rotating turbulent pipe flow in a manner similar to the case in a turbulent swirling flow, whose behaviors appeared to be totally different from each other.
The turbulent helicity has been expected to be one of the important turbulent quantities in describing the large-scale structures in tubulent flows. It is, however, true that information on turbulent helicity has been lacking in the study of turbulence. This made it difficult to appropriately simulate turbulent flows with a turbulence model adopting the helicity as a basic statistical quantity. In this research, data of the representative experiment of turbulent swirling flows were re-examined from the viewpoint of the turbulent helicity. The analysis revealed what mechanism is dominant in producing the turbulent helicity.
Another improvement is attained in relation to the eccentricity of the turbulent swirling flow in the center region. The highly asymmetric mean-velocity profiles in the center region observed in the experiments were calibrated with the aid of physical arguments such as the symmetry and conservation properties of the swirling flow. It is expected that this calibrated profiles provide a firm basis for the numerical simulation of the turbulent swirling flow.
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