| Project/Area Number |
10650185
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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 |
Fluid engineering
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| Research Institution | Osaka City University |
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Principal Investigator |
AZUMA Tsuneo Osaka City University, Faculty of Engineering, Professor, 工学部, 教授 (40047329)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1998: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | Laminar-Turbulent Transition / Atomization / Liquid Film Flow / Instability / Droplet / Boundary Layer / 境界層 |
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| Research Abstract |
Water is radially dischanged from a nozzle through a small gap between the nozzle and a disk to form a liquid film in which laminar boundary layer type velocity distribution is developed even on the liquid surface, and the liquid film flows radially into the air. In the thus formed radial liquid sheet, a large number of perforations are generated immediately after the laminar-turbulent transition when the liquid film is thin and the discharge Reynolds number is large, and as a result, the liquid film is atomized. Detailed observation of the point near the occurrence of transition revealed that the transition, perforation and atomization of the liquid film occur by the following process.
(1) Appearance of the rippled concentric waves (D waves) and formation of wavy irregularities by three-dimensional conversion of the D waves.
(2) Concentrated formation (laminar-turbulent transition) of the fine-granular waves (SL waves) at the convex part and formation of the wavy liquid aggregates by concentration of the granular waves. Formation of thin membranes due to the thinning of the concave parts of the film.
(3) Perforation at the membranes and expansion of the perforations. Formation of droplets of 20-30 mm in size by separation of the microprojections at the peripheral parts of the liquid aggregates (microprojection separation-type breakup).
(4) Deformation of the liquid aggregates into monoliform liquid strands and formation of drops of 300-500 mm in size by the breaking of the liquid strands (liquid aggregate disintegration-type breakup).
In addition, we clarified that when transition occurs on a disk due to a high discharge Reynolds number or disk rotation, perforation is highly suppressed ; we also showed conditions in which atomization occurs due to microprojection separation-type breakup.
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