Simulation models for unsteady dispersed multiphase flows
Project/Area Number  08650208 
Research Category 
GrantinAid for Scientific Research (C)

Section  一般 
Research Field 
Fluid engineering

Research Institution  Ehime University 
Principal Investigator 
AYUKAWA Kyozo Ehime University, President, 学長 (30036230)

CoInvestigator(Kenkyūbuntansha) 
KAWAHARA Genta Ehime University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (50214672)
OCHI Junji Ehime University, Faculty of Engineering, Professor, 工学部, 教授 (00036245)

Project Fiscal Year 
1996 – 1997

Project Status 
Completed(Fiscal Year 1997)

Budget Amount *help 
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1996 : ¥1,500,000 (Direct Cost : ¥1,500,000)

Keywords  Multiphase Flow / Bubbly Flow / Numerical Simulation / Gravitational Field / Bubbly Plume / 混相流 / 気泡流 / 数値シミュレーション / 重力場 / 気泡プリューム / 非定常 / 分散性 
Research Abstract 
The earlytime evolution of twodimensional flows induced by rising small bubbles, which are released at short intervals on the bottom of an open vessel, has been examined by using a new numerical method. In the present method, the variation of the relative liquid velocity along bubble trajectories is approximately represented to be piecewise linear, and the shorttime motion of discrete bubbles is described in terms of the exact solution to the full BassetBoussinesqOseen (BBO) equation for constant fluid acceleration. Bubbly fluid is then assumed to be a continuum, the mass desity and the viscosity of which fluctuate in space and time via intermittent existence of moving bubbles, and the velocity and pressure of the bubbly fluid is obtained from numerical integration of the NavierStokes and continuity equations. The numerical method to be proposed in this study has the following significant advantages : The use of the exact solution to the BBO equation reduces both computer mem
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ory and CPU time necessary to numerically analyze the motion of a large number of bubbles. The use of the full BBO equation makes it possible to take into account the historical effects on bubble behavior, which are represented by the socalled Basset term and often neglected without any consensus for the difficulty in its numerical treatment. We applied this method to numerical simulations of the transient bubbly flow in a twodimensional vessel of a square crosssection under the effect of the gravity. The validity of this method has been confirmed by comparing the numerical results with the experimental ones. In this application, we have shown that the whole flow becomes highly asymmertric and plume exhibits unstable meandering, when relatively small bubbles are released with their arrangement being symmetric with respect to the vessel centerline. In addition, it is observed that the flow recovers its symmetry and the plume is stabilized if we introduce relatively large bubbles into the unstable above flow by adding the large ones to the symmetric arrangement of the small ones. Less

Report
(4results)
Research Output
(8results)