In order to study in detail effects unique to two-phase flow in helically coiled pipes a mechanistic two-phase flow model has been developed which is based on the RELAP5/MOD3 two-fluid mode, however with new and improved correlations for flow regime mapping, stratification and wall shear and heat transfer. The point of transition to stratified flow has been modified based on the Kelvin-Helmholtz stability criterion to better represent stratification onset in coiled pipes. Centrifugal forces acting on the flow has been accounted for by a modified body force with a subsequent nearly-implicit coupling in the momentum equations and a set of correlations representing the phasic wall friction factors and two-phase multipliers have been included in the code though in a modified form. This presentation summarizes the new correlations and the overall influence of the curvature of the flow path on the two-phase flow is estimated using a sample benchmark.

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The effective viscosity of bubbly liquid is governed not only by void fraction but also by bubble's deformation whose effect is expressed with Capillary number. In this study, two kinds of bubbly two-phase flow are analyzed with using the model of the effective viscosity to confirm the effect of bubble's deformation on the time-averaged velocity profiles in laminar flow conditions.

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Flow with three-dimensional time-dependent phenomena of silicon melt in an electromagnetic Czochralski (EMCZ) system with transverse magnetic fields was numerically investigated. This paper focused on the effect of electrode positions and direction of electric current on heat and oxygen transfer in the melt. The results showed that the case with current flow perpendicular to the magnetic fields can modify heat and oxygen transfer in the melt. The also results showed that electric current flow perpendicular to the applied transverse magnetic fields enhanced heat and oxygen transfer from crucible to a crystal in the melt.

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This paper describes application of the vector finite element method to the induction equations. It is well known that the vector finite element method is one of the powerful tools for solving electromagnetic problems. Using vector finite element method, the solenoidal condition for the magnetic flux density satisfies automatically in time increment. This is because the arrangement of variables, which are on the center of the face for the magnetic field and on the center of the edge for the electric field in an element. In this presentation, numerical scheme using vector finite element method for induction equations are developed to investigate magnetohydrodynamics.

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Drag reduction caused by surfactant solutions is considered. Surfactant contains threadlike micelles. At a critical shear rate the shear viscosity suddenly increases in this so-called shear-induced state (SIS). At high shear rates the increased shear viscosity gradually decreases. In this paper, two-dimensional numerical simulation in the surfactant solution containing threadlike micelles by the finite difference lattice Boltzmann method is reported. As a result, we formed SIS and checked the shear viscosity increasing at a critical shear rate and the increased shear viscosity decreasing at high shear rates.

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This paper reports the finite difference lattice Boltzmann method (FDLBM) built in the turbulence model. This model is built in the subgrid model, which incorporates the standard Smagorinsky model to damp the small-scale fluctuations from the flow field. First, we show the theory of the FDLBM subgrid model, and then we simulate three-dimensional fully developed turbulent channel flow at Re_τ=150 using this method, and compare it with DNS database. The result of FDLBM subgrid model shows appropriate agreement with that of DNS database if a shortage of calculation lattice is considered.

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Computation of 3-dimensional homogeneous isotropic turbulence by the Finite Difference Lattice Boltzmann Method (FDLBM) has been conducted with the grids of 64×64×64. In the case of freely decaying homogeneous turbulence, the energy spectrum obtained by the FDLBM is compared with the experimental result. In the case of forced turbulence, a comparison of turbulence by the FDLBM and FDS are conducted.

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A steam control valve causes vibration of the piping when the opening is in the middle condition. For the rationalization of maintenance and management in the plant, the cause of vibration should be clarified and the valve should be improved. To clarify this phenomenon, small-scale air experiment and CFD calculation are done. At only the middle opening condition, a circumferentially propagating spike-type pressure fluctuation caused by asymmetric flow around valve can be seen. As this fluctuation causes cyclic side load on the valve body, it is thought to be the cause of vibration.

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[in Japanese]

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A High accurate implicit scheme based on IDO scheme for solving a wide variety of partial differential equations has been developed. By using implcit Runge-Kutta time integration, we can construct the implicit scheme with high accuracy and stability for a multi-dimensional case. It is shown that the numerical solutions for the two-dimensional advection equation and diffusion equation are equal to that of the explicit scheme for a large time interval. As examples of non-linear problems, we solved one and two-dimensional burgers equations and obtained high accurate result for a large CFL number.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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In the context of a collaboration between JNC and CEA, we focus on turbulent thermal hydraulic flows in mixing tee geometries which are widely used in nuclear technology. Both experimental and numerical simulations where performed. In this preliminary work, we compare numerical results obtained by the TRIO_U/PRICELES code with measurements obtained at JNC (see [1]). PRICELES is the module from CEA's R & D platteform for thermal hydraulic (TRIO_U) dedicated to Large Eddy Simulation for incompressible flows (see [2]). It's a parallel application dealing with either structured (MAC like) or unstructured (Finite Volume Element) grids (see [3,4]). In this first simulation we used an about one million cells structured grid and a selective structure function subgrid-scale model (see [5]). As a first stage, a mixing tee configuration with small buoyancy force and a main pipe velocity 1.46 times higher than the branch pipe one has been selected. The velocity and temperature fields obtained by the LES computation shows good agrement both for the mean and rms values with the measured ones. An unstructured mesh computation using a new finite volume element method (see [6]) is now planned.

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We present some preliminary results from validation tests for a cavitation model that was proposed by Okita, et al. This model assumes that the cavitating flow is of homogeneous mixture of the liquid phase and vapor phase and empirically correlates the generation (dissipation) of vapor phase with the difference between the ambient pressure and vapor pressure of the fluid. The model was applied to the computation of two types of unsteady cavitating flows in conjunction with the large eddy simulation based on the dynamic Smagorinsky model : unsteady wake of a rectangular cylinder (prism) at a Reynolds number of (10)^4 and turbulent boundary layer that develops on a Clark-Y 12% thickness hydrofoil at a chord-based Reynolds number of 5.0×(10)^5. In both cases we obtained reasonably good agreements with the corresponding measured data.

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A three-dimensional unstructured finite-volume method is used to investigate laminar flow characteristics of a miniature chamber with a possible application to micro gas turbine combustor design. The chamber is cylindrical in shape and a baffle plate is installed at its entrance having one fuel jet located at the center and six oxidizer jets deployed to surround the fuel jet. Attention is given to the effect of the inlet conditions on the flow structure and mixing pattern inside the chamber. Computations are carried out with the calculation domain inlet being positioned at two different locations. Numerous inlet conditions are examined including 'top-hat', fully-developed, swirling, annular backward-facing step and some asymmetrically skewed profiles. The baffle plate is shown to have a significant smoothing effect on the inlet conditions for a Reynolds number of 100. However, for larger Reynolds number, the flow stability is more sensitive to the upstream conditions. In some cases, asymmetric profiles are obtained downstream of the baffle plate.

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The lattice Boltzmann method for multicomponent immiscible fluids is applied to the simulations of wetting dynamics. The wetting is introduced by using the wetting potential proposed by Briant et al. We apply the the method to the flow in a micro channel with homogeneous and heterogeneous wetting walls, and find that the interface is advanced by a capillary force, and that the interface is disordered in the case that the wall has heterogeneous wetting.

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In the present study, molecular dynamics simulation is applied to the analysis of bubble nucleation in the Lennard-Jones liquid including gas impurities. Through the simulation, it is found that the gas whose interaction is very weak and whose diameter is larger than that of solvent fairly raises the nucleation point because the fluctuation in liquid becomes large and more frequent even if the concentration is very low. While in the case in which the interaction of impurity is fairly strong, the effect of diameter to the fluctuation in liquid and the limit of superheat is a little. In addition, the simulation of bubble nucleation in the larger computational domain is executed, and it is observed that two nuclei are formed and these interactions change the growth speed of nucleated void volume.

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Recently a cell membrane and a liposome are studied actively in the field of medical engineering such as the Drug Delivery System and the artificial oxygen carrier. Basically they have the common structure of a lipid bilayer. Although the elucidation of the molecular transportation through the lipid bilayer membranes is very important in such a biochemical process, experimental observation has much difficulty and even the mechanism of a molecular penetration is not understood clearly. Hence, in this research, the transport characteristic of the lipid bilayer was analyzed using molecular dynamics method. We calculated the excess chemical potential profiles of the small molecules across the lipid bilayer using cavity insertion Widom method. The three dimensional potential field was also calculated. We found that the vdW (van del Waals) potential field drastically changes with z coordinates. In the calculation of the electrostatic potential field, the contribution from the lipid molecules and water molecules were calculated separately, and we found that the each profile has own characteristic.

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