scispace - formally typeset
Search or ask a question
Author

Isao Kataoka

Bio: Isao Kataoka is an academic researcher from Osaka University. The author has contributed to research in topics: Two-phase flow & Turbulence. The author has an hindex of 16, co-authored 75 publications receiving 1272 citations.
Topics: Two-phase flow, Turbulence, Bubble, Boiling, Heat flux


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a simple but reliable correlation for a drag coefficient, CD, of single bubbles under a wide range of fluid properties, bubble diameter and acceleration of gravity were developed based on a balance of forces acting on a bubble in a stagnant liquid and available empirical correlations of terminal rising velocities of single bubble.
Abstract: Simple but reliable correlations for a drag coefficient, CD, of single bubbles under a wide range of fluid properties, bubble diameter and acceleration of gravity were developed based on a balance of forces acting on a bubble in a stagnant liquid and available empirical correlations of terminal rising velocities of single bubbles. The proposed CD consists of three equations, each of which corresponds to pure, slightly contaminated and contaminated systems. The effect of a frictional pressure gradient due to a liquid flow is also taken into account by introducing a concept of an effective body acceleration. Terminal rising velocities of single bubbles were calculated using the proposed CD, and compared with measured data under the condition of 10-2

517 citations

Journal ArticleDOI
TL;DR: In this article, a simple model for entrainment rate in annular two-phase flow has been developed from a simple 3D model in collaboration with data, and a simple approximate correlation has been obtained for the equilibrium state where entraining rate and deposition rate become equal.

123 citations

Journal ArticleDOI
TL;DR: In this paper, the rise characteristics of spherical and ellipsoidal bubbles in normal and high-temperature distilled water were visually observed and the existence of rise path oscillation roughly agreed with the correlations for the bubbles in contaminated liquid.

95 citations

Journal ArticleDOI
TL;DR: In this article, the rate of droplet entrainment is characterized by the ratio of the interfacial shear force to the surface tension force acting on the phase interface in annular-dispersed two-phase flow.

84 citations

Journal ArticleDOI
TL;DR: In this paper, a new set of correlations for the film flow analysis was developed to predict the critical heat flux in annular flow regime accurately, which required no parameters that should be adjusted from the measured data of critical flux.
Abstract: A new set of correlations for the film flow analysis was developed to predict the critical heat flux in annular flow regime accurately. All the correlations adopted here were based on experimental data or considerations of the processes in annular flow; the resulting model required no parameters that should be adjusted from the measured data of critical heat flux. The 4,375 data of critical heat flux in forced flow of water in vertical uniformly heated round tubes were used to test the basic performance of the model. The comparisons between the calculated and measured critical heat fluxes showed that the predicted results by the present model agree with the experimental data fairly well if the flow pattern at the onset of critical heat flux condition is considered annular flow. The predictive capability was not deteriorated even in the cases of small diameter tube, short length tube as well as low vapor quality. Good agreements were also achieved in the preliminary tests against the critical heat flux dat...

81 citations


Cited by
More filters
Dissertation
01 Jan 2003
TL;DR: In this paper, the authors describe the development and validation of Computational Fluid Dynamics (CFD) methodology for the simulation of dispersed two-phase flows, which employs averaged mass and momentum conservation equations to describe the time-dependent motion of both phases.
Abstract: This study describes the development and validation of Computational Fluid Dynamics (CFD) methodology for the simulation of dispersed two-phase flows. A two-fluid (Euler-Euler) methodology previously developed at Imperial College is adapted to high phase fractions. It employs averaged mass and momentum conservation equations to describe the time-dependent motion of both phases and, due to the averaging process, requires additional models for the inter-phase momentum transfer and turbulence for closure. The continuous phase turbulence is represented using a two-equation k − ε−turbulence model which contains additional terms to account for the effects of the dispersed on the continuous phase turbulence. The Reynolds stresses of the dispersed phase are calculated by relating them to those of the continuous phase through a turbulence response function. The inter-phase momentum transfer is determined from the instantaneous forces acting on the dispersed phase, comprising drag, lift and virtual mass. These forces are phase fraction dependent and in this work revised modelling is put forward in order to capture the phase fraction dependency of drag and lift. Furthermore, a correlation for the effect of the phase fraction on the turbulence response function is proposed. The revised modelling is based on an extensive survey of the existing literature. The conservation equations are discretised using the finite-volume method and solved in a solution procedure, which is loosely based on the PISO algorithm, adapted to the solution of the two-fluid model. Special techniques are employed to ensure the stability of the procedure when the phase fraction is high or changing rapidely. Finally, assessment of the methodology is made with reference to experimental data for gas-liquid bubbly flow in a sudden enlargement of a circular pipe and in a plane mixing layer. Additionally, Direct Numerical Simulations (DNS) are performed using an interface-capturing methodology in order to gain insight into the dynamics of free rising bubbles, with a view towards use in the longer term as an aid in the development of inter-phase momentum transfer models for the two-fluid methodology. The direct numerical simulation employs the mass and momentum conservation equations in their unaveraged form and the topology of the interface between the two phases is determined as part of the solution. A novel solution procedure, similar to that used for the two-fluid model, is used for the interface-capturing methodology, which allows calculation of air bubbles in water. Two situations are investigated: bubbles rising in a stagnant liquid and in a shear flow. Again, experimental data are used to verify the computational results.

968 citations

Journal ArticleDOI
TL;DR: In this article, trajectories of single air bubbles in simple shear flows of glycerol-water solution were measured to evaluate transverse lift force acting on single bubbles, and the authors concluded that the critical bubble diameter causing the radial void profile transition from wall peaking to core peaking in an air-water bubbly flow evaluated by the proposed CT correlation coincided with available experimental data.

855 citations

Journal ArticleDOI
TL;DR: In this article, the kinematic constitutive equation for the drift velocity has been studied for various two-phase flow regimes, and a comparison of the model with various experimental data over various flow regimes and a wide range of flow parameters shows a satisfactory agreement.

799 citations

Journal ArticleDOI
Abstract: The formation of gas bubbles and their subsequent rise due to buoyancy are very important fundamental phenomena that contribute significantly to the hydrodynamics in gas−liquid reactors. The rise o...

657 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the primal cause of widely scattered VT in this regime is not surfactant concentration but initial shape deformation, and the primal role of surfactants is to cause damping of shape oscillation, by which a contaminated bubble behaves as if it were a clean bubble with low initial shape deformations.

407 citations