scholarly journals Constitutive Equations for Two-Fluid Model Used in Thermal-Hydraulic Analyses

1992 ◽  
Vol 6 (1) ◽  
pp. 35-53
Author(s):  
Kaichiro MISHIMA
Keyword(s):  
Constitutive Equations ◽  
Fluid Model ◽  
Two Fluid Model ◽  
Two Fluid

Analyses of Hydrodynamic Structure of Water Jet and Its Application to Jet Grouting

2003 ◽  
Author(s):  
Kenji Yoshida ◽  
Isao Kataoka ◽  
Hiroshi Yoshida ◽  
Mitsuru Yokoo ◽  
Kiyoshi Horii
Keyword(s):  
Constitutive Equations ◽  
Fluid Model ◽  
Momentum Conservation ◽  
Water Jet ◽  
Two Phase ◽  
Dispersed Flow ◽  
Two Fluid Model ◽  
Basic Equations ◽  
Physical Phenomena ◽  
Two Fluid

Analyses of water jet based on two-fluid model of two-phase dispersed flow have been carried out for single water jet and cross water jet in relation to the water jet technology in civil engineering. Mass and momentum conservation equations for liquid phase (droplet) gas phase (air) were formulated separately (two-fluid model formulation). Physical modeling of diffusion of droplets, drag coefficient of droplet in dispersed flow, shear stress at jet interface, etc has been carried out in detail and constitutive equations for these physical phenomena have been developed. Based on the two-fluid model basic equations and constitutive equations, one-dimensional analysis has been carried out considering simplified model. In the practical application of present analyses, some preliminary analyses on cross jet where two water jets collide with certain collision angles have been carried out and the predicted results reasonably explain the experimental results.

Development of Advanced Two-Fluid Model for Boiling Two-Phase Flow in Rod Bundles

2010 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Hideaki Hosoi ◽  
Takayuki Suzuki ◽  
Kazuyuki Takase
Keyword(s):  
Constitutive Equations ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Interface Tracking ◽  
Phase Flow ◽  
Rod Bundles ◽  
Two Phase ◽  
Tracking Method ◽  
Two Fluid Model ◽  
Two Fluid

Two-fluid model can simulate two-phase flow by computational cost less than detailed two-phase flow simulation method such as interface tracking method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as rod bundles in nuclear reactors. However, two-fluid model include a lot of constitutive equations. Then, applicability of these constitutive equations must be verified by use of experimental results, and the two-fluid model has problems that the results of analyses depend on accuracy of constitutive equations. To solve these problems, we have been developing an advanced two-fluid model. In this model, an interface tracking method is combined with the two-fluid model to predict large interface structure behavior accurately. Interfacial structures larger than a computational cells, such as large droplets and bubbles, are calculated using the interface tracking method. And droplets and bubbles that are smaller than cells are simulated by the two-fluid model. Constitutive equations to evaluate the effects of small bubbles or droplets on two-phase flow are required in the advanced two-fluid model as same as a conventional two-fluid model. However, dependency of small bubbles and droplets on two-phase flow characteristic is relatively small, and the experimental results to verify the equations are not required much. In this study, we modified the advanced two-fluid model to improve the stability of the numerical simulation and reduce the computational time. Moreover, the modified model was incorporated to the 3-dimensional two-fluid model code ACE-3D. In this paper, we describe the outline of this model and the modification performed in this study. Moreover, the numerical results of two-phase flow in various flow conditions.

Model Development of Turbulent Dispersion Force for Advanced Two-Fluid Model in Consideration of Bubble-Liquid Phase Interactions

2010 ◽  
Author(s):  
Hideaki Hosoi ◽  
Hiroyuki Yoshida
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Constitutive Equations ◽  
Fluid Model ◽  
Turbulent Dispersion ◽  
Dispersion Force ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

Two-fluid model can simulate two-phase flow by computational cost less than detailed two-phase simulation method such as interface tracking method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as rod bundles. However, since two-fluid model include a lot of constitutive equations, applicability of these constitutive equations must be verified by use of experimental results, and the two-fluid model has problems the result of analyses depends on accuracy of constitutive equations. To solve these problems, an advanced two-fluid model has been developed in Japan Atomic Energy Agency. In the model, an interface tracking method is combined with the two-fluid model to predict large interface structure behavior accurately. Liquid clusters and bubbles larger than a computational cell are calculated using the interface tracking method, and those smaller than a cell are simulated by the two-fluid model. Constitutive equations to evaluate the effect of small bubbles or droplets on two-phase flow required in the advanced two-fluid model as same as a conventional two-fluid model. However, dependency of small bubbles and droplets on two-phase flow characteristic is relatively small, and the experimental results to verify the equations are not required much. The turbulent dispersion force term is one of the most important constitutive equations for the advanced two-fluid model. The turbulent dispersion force term has been modeled by many researchers for the conventional two-fluid model. However, the existing models include effects of large bubbles and deformation of bubbles implicitly, these models are not applicable to the advanced two-fluid model. In this study, we develop the new model for turbulent dispersion force term. In this model, effect of large bubbles and deformation of bubbles are neglected. The liquid phase turbulent kinetic energy and bubble-induced turbulent kinetic energy are considered to evaluate driving force in the turbulent diffusion of small bubbles. The bubble-induced turbulent kinetic energy is given by the function of bubble diameter and local relative velocity, and the liquid phase turbulent kinetic energy is similar to the single phase flow case. Furthermore, we considered energy transfer from the bubble-induced kinetic energy to the liquid phase turbulent kinetic energy. To verify the developed model, the advanced two-fluid model and the model for turbulent dispersion term were incorporated to the 3-dimensional two-fluid model code ACE-3D, and comparisons between the results of analyses and air-water two-phase flow experiments in 200 mm diameter vertical pipe were performed.

Analyses Hydrodynamic Structure of Cross Water Jet and Its Performance of Soil Improvement

2005 ◽  
Author(s):  
Mitsuhiro Shibazaki ◽  
Hiroshi Yoshida ◽  
Kenji Yoshida ◽  
Kiyoshi Horii ◽  
Isao Kataoka
Keyword(s):  
Constitutive Equations ◽  
Fluid Model ◽  
Soil Improvement ◽  
Momentum Conservation ◽  
Water Jet ◽  
Two Phase ◽  
Dispersed Flow ◽  
Hydrodynamic Structure ◽  
Two Fluid Model ◽  
Two Fluid

Analyses of water jet based on two-fluid model of two-phase dispersed flow have been carried out for single water jet and cross water jet in relation to the water jet technology in civil engineering. Mass and momentum conservation equations for liquid phase (droplet) gas phase (air) were formulated separately (two-fluid model formulation). Physical modeling of diffusion of droplets, drag coefficient of droplet in dispersed flow, shear stress at jet interface, etc has been carried out in detail and constitutive equations for these physical phenomena have been developed. Based on the two-fluid model basic equations and constitutive equations, one-dimensional analysis has been carried out considering simplified mode and hydrodynamic structure of water jet was well predicted. In the practical application of present analyses, some preliminary analyses on cross jet where two water jets collide with certain collision angles have been carried out and the predicted results reasonably explain the experimental results.

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