1998 Fiscal Year Final Research Report Summary
Study on a quantitative measurement using laser induced fluorescence and a model of bubble motion in linear shear flows
| Project/Area Number |
08650205
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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 | KOBE UNIVERSITY |
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Principal Investigator |
TOMIYAMA Akio Kobe University, Graduate School of Science and Technology, Associate Professor, 自然科学研究科, 助教授 (30211402)
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| Co-Investigator(Kenkyū-buntansha) |
HOSOKAWA Shigeo Kobe University, Graduate School of Science and Technology, Associate Professor, 自然科学研究科, 助教授 (10252793)
SAKAGUCHI Tadashi Kobe University, Faculty of Engineering, Professor, 工学部, 教授 (50031076)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Bubble / Model of bubble motion / Laser induced fluorescence / Lift force |
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| Research Abstract |
Trajectories of single air bubbles in linear shear flows of glycerol-water solution were measured to evaluate transverse lift force acting on a bubble. Experiments were conducted under the conditions of -5.5 <less than or equal> log M <less than or equal> -2.8, 1.39 <less than or equal> Eo <less than or equal> 5.74 and 0 <less than or equal> "*"dV_L/dy"*" <less than or equal> 8.3s^<-1>, where M is the Morton number, Eo the Eotvos number and dV_L/dy the velocity gradient of the linear shear flow of liquid. Making use of all the measured trajectories and an equation of bubble motion, a net transverse lift coefficient C_T was evaluated. The C_T for small bubbles was found to be well correlated with the bubble Reynolds number, whereas C_T for large bubbles was well correlated with a modified Eotvos number, which was defined by using the maximum horizontal dimension of a deformed bubble as a characteristics length. The resulting C_T correlation is given by the following equations.
The critic
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al bubble diameter causing the radial void profile transition from wall peaking to core peaking in an air-water bubbly upflow was evaluated with the C_T correlation as 5 to 6 mm, which is in good agreement with available experimental data on radial void profiles. It is possible to predict the most probable radial position of a bubble in a bubbly upflow in a vertical pipe using a simple force balance between the net transverse lift force and wall force.
To measure detailed wake structure behind single bubble, a non-intrusive measurement technique using laser induced fluorescence was developed and evaluated. It was confirmed that the present method can measure the phase distribution function and the liquid velocity simultaneously with high spatial and time resolutions. The measured results indicates that the wake structure was dominated by the maximum horizontal dimension of a deformed bubble rather than the equivalent diameter of the bubble, and the liquid velocity gradient induced the deformation of the bubble wake. Less
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