1997 Fiscal Year Final Research Report Summary
Study on the Enhancement of Gas Absorption into a Falling Liquid Film Caused by Surface Waves and Modelling of the Gas Absorption
| Project/Area Number |
08650270
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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 | University of the Ryukyus |
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Principal Investigator |
NOSOKO Takehiro University of the Ryukyus, Faculty of Engineering Associate Professor, 工学部, 助教授 (80183903)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Falling Liquid Film / Surface Wave / Gas Absorption / Mass Transfer / Vorticity |
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| Research Abstract |
To understand why the surface waves drastically enhance the gas absorption into a falling liquid film and model the absorption, we investigated the dynamics of three-dimension surface waves on the falling liquid film. The major results of this investigation may be summarized as follows.
Surface waves separated well from each other (solitary waves) were excited on a water film falling down a vertical surface by introducing controlled temporal disturbances of constant frequencies into the film entrance, and the response of the waves to spatial disturbances generated by perturbations located just below the film entrance is analyzed. The results show that the two-dimensional waves of small phase velocities are unstable to spatial disturbances of large wavelengths and transform into three-dimensional waves having sinusoidal wave fronts, while the waves of intermediate and large phase velocities are unstable to small wavelength disturbances and their wave fronts bend to form several U-shapes on each front. The U-shapes (or ' s) originate from the perturbations, U' and they align in a row with the corresponding perturbations. When a single perturbation is put on the film, a 'U' orginating from the perturbation leads to the generation of a new 'U' on either side, i.e.a self-induced lateral propagation occurs.
It is pointed out that these surface waves hold vortices occurring in a shear layr bounded by a solid surface and a free liquid-gas interface, and the U-shaped waves resemble both the LAMBDA-vortices and horseshoe-shaped vortices observed in boundary layrs on walls.
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