2006 Fiscal Year Final Research Report Summary
Double Diffusive phenomena in Environment
| Project/Area Number |
15560192
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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 |
Thermal engineering
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| Research Institution | Toyama National College of Technology |
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Principal Investigator |
KAMAKURA Katsuyoshi Toyama National College of Technology, Department of Chemical and Bio-chemical Engineering, Professor, 物質工学科, 教授 (40042832)
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| Project Period (FY) |
2003 – 2006
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| Keywords | Meteorology / Living environment / Oceanography / Chemical Engineering |
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| Research Abstract |
The double diffusive natural convection arises owing to the rate difference between thermal and solutal diffusions in a fluid containing temperature and concentration gradients. The double diffusive convections of pollutant in air are encountered in various situations of environment, such as smog, smoke, fire and heat island. Then the characteristic phenomena of double diffusive convection are observed as follows : (1) multi-layered convection, (2) interleaving phenomenon, (3) salt-finger phenomenon, (4) oscillation of flow, (5) fluctuation of flow, (6) bifurcation of flow. Numerical analyses of double diffusive convection were numerically carried out for the various environmental situations.
(1) Double diffusive phenomena in main flow
The double diffusive convection of hot block solution was studied in main flow At buoyancy ratio N<1, the hot block solution spreads beneath the top surface and develops to salt-fingers with the diffusion of heat. At N>=1, the hot block solution dropped with complicated heads and a tail, and accumulates on the bottom.
(2) Double diffusive plume phenomena
The double diffusive convection of ascending thermal plume in the air having a linear concentration gradient was numerically analyzed at N=0 to 1. The ascending plume due to thermal buoyancy stops at a lower position with the increase of buoyancy ratio. Then, the descending current is formed outside the ascending thermal plume owing to the solutal buoyancy. The surface of thick ascending plume becomes odd-shaped owing to the descending flow with time.
(3) Solar pond
The double diffusive phenomena in solar pond were studied for a two-layer system which consists of a pure water (upper layer) and an aqueous solution (lower layer) with the heating from the entire bottom. The heat from the source on the bottom accumulates owing to thermal plumes in the lower layer efficiently in the case of both large buoyancy ratio and high Rayleigh number.
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