On the Effect of Stably Stratified Layer to the Development of Free Convection
| Project/Area Number |
16540402
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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 |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
KARASUDANI Takashi KYUSHU UNIVERSITY, Institute for Applied Mechanics, Associate Professor, 応用力学研究所, 助教授 (30150527)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | stably stratified / mixed layer / inversion layer / air-sea exchange / stripe structures / turbulent transport / buoyancy driven turbulence / free convection / 対流 / 混合層 / 乱流 / 交換過程 / 熱輸送 / 筋状構造 / 大気-海洋境界面 |
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| Research Abstract |
Turbulence structure and transport process beneath the gas-liquid interface is important in air-sea interaction and in many industrial operations. As, in stably stratified circumstances (with inversion layer), turbulence parallel to vertical direction is suppressed, turbulence structure is expected to be affected greatly. To clarify the effect, we experimentally and numerically studied the development and statistical properties of a free convective layer under a water surface. Velocity and temperature fluctuations were simultaneously measured by a laser-Doppler velocimeter and a fine thermocouple. Variances and correlations for the fluctuations were normalized by the kinematic heat flux and the thickness of the convective layer, and vertical profiles of those quantities were obtained.
Their profiles were compared with those for neutral circumstances (without inversion layer). The variance of the horizontal velocity decrease more slowly near the inversion layer, compared to neutral circumstances. The value of the correlation between temperature and vertical velocity became positive near the inversion layer, whereas the value was always non-positive in neutral circumstances.
The situation was numerically simulated by DNS method. The calculated profiles of the variances were consistent with the experimental ones. By the simulation with various boundary conditions at the surface, it was found that stripe structure, which appeared in near the surface, was supposed to be generated by shear stress at the surface. There was no significant difference for the variances by the difference of the boundary conditions.
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Report
(3 results)
Research Products
(3 results)
