Flow Analysis Code Research Articles

2206 FEM流体解析用知的GUIの開発(OS10-1 ヒューマンインタフェース・ユーザビリティI)

A GUI system for a fluid flow analysis code, Front/Flow/Blue (FFB), has been developed. This is an integrated system of pre-post processing tools, the FFB and a user-friendly GUI. This paper describes capabilities of the GUI system, especially its intellectual aspects.

1442 微小分岐部に振動流を与えることによる揚水効果(S38-3 マイクロチャンネル,S38 マイクロ・ナノフルイズ)

The pumping effectiveness of the micro T-junction with the oscillatory flow was examined. At one end of the top bar of T, there was a closed tank; Tank 1, that was solid with water. At another end of the top bar of T, there was a tank; Tank 2, that was open to the atmosphere. At the bottom end of the vertical branch of T, there was also a tank; Tank 3, that was open to the atmosphere. In Tank 2 and Tank 3, free surface of water was formed. The 1mm×1 mm cross-section flow path of the 20mm long top bar and 10mm long vertical branch of T were filled with water. By causing boiling and condensation of a bubble cyclically in Tank 1, back-and-forth flow was created at the T-junction. Water surface level in Tank 2 was higher than that in Tank 3. Difference between surface level height in Tank 2 and in Tank 3 was mainly dominated by a back-and-forth velocity at the T-junction. The flow system tested in experiments was simulated by a commercial flow analysis code of STAR-CD. It was confirmed that mass relocation from Tank 3 to Tank 2 occurred when the back-and-forth flow was imposed at the T-junction. The vortical movement around the entry of the branch to Tank 3 that was caused by the back-and-forth flow seemed to cause mass relocation, i.e. the level height difference between Tank 2 and Tank 3.

Development of a flow analysis code using an unstructured grid with the cell-centered method

A conservative finite-volume numerical method for unstructured grids with the cell-centered method has been developed for computing flow and heat transfer by combining the attractive features of the existing pressure-based procedures with the advances made in unstructured grid techniques. This method uses an integral form of governing equations for arbitrary convex polyhedra. Care is taken in the discretization and solution procedure to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. For both convective and diffusive fluxes the forms superior to both accuracy and stability are particularly adopted and formulated through a systematic study on the existing approximation ones. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are computed by using a linear reconstruction based on the divergence theorem. Momentum interpolation is used to prevent the pressure checkerboarding and a segregated solution strategy is adopted to minimize the storage requirements with the pressure-velocity coupling by the SIMPLE algorithm. An algebraic solver using iterative preconditioned conjugate gradient method is used for the solution of linearized equations. The flow analysis code (PowerCFD) developed by the present method is evaluated for its application to several 2-D structured-mesh benchmark problems using a variety of unstructured quadrilateral and triangular meshes. The present flow analysis code by using unstructured grids with the cell-centered method clearly demonstrate the same accuracy and robustness as that for a typical structured mesh.

Numerical Simulation of the Effect of Processing Parameters on the Flow Behavior and Break-through Phenomenon in Co-Injection Molding

Abstract In this work, a three-dimensional finite element flow analysis code is used to study the flow behavior during sequential co-injection molding. Non-Newtonian, non-isothermal flow solutions are obtained by solving the momentum, continuity and energy equations. Two additional transport equations are solved for tracking polymer/air and skin/core polymers interfaces. Solutions are presented for the filling of a spiral-flow mould for which experimental measurements are available. The numerical approach is shown to predict the core advance stage during which the core flow front catches up on the skin flow front and the core expansion phase when the flow fronts of core and skin materials advance together without breakthrough. The breakthrough phenomenon is also predicted and the numerical solution is in good agreement with the experiment. Those phenomena are hard to predict numerically and to our knowledge this is the first attempt at simulating the three-dimensional melt behavior during core expansion and core breakthrough. The predicted flow front behavior is compared to the experimental observations for various skin/core melt temperature, skin/core viscosity ratio, and core injection delay. Simulation results are in good agreement with experimental data and indicate correctly the trends in solution change when processing parameters are changing.

Experimental and Numerical Study of a Dual-mode Scramjet Combustor

A Mach 2, hydrogen-air combustor with an unswept 10-deg ramp fuel injector was experimentally and numerically studied for a simulated flight Mach number near 5. Numerical modeling was performed using the Viscous Upwind Algorithm for Complex Flow Analysis code, and results were compared against experimental wall-pressure distributions, fuel plume images, and fuel plume velocity measurements. The model matched wall-pressure distributions well for the case of fuel-off and fuel-air mixing. For a fuel-air reacting case, pressure was matched well in the upstream third of the duct. Downstream, however, the pressure rise as a result of combustion was underpredicted. Based on the fuel plume imaging and velocity measurements, fuel plume shape was matched well for both the mixing and reacting cases. However, plume size, penetration, and centerplane axial growth were generally underpredicted by the model. The full extent of the velocity reduction caused by thermal choking was also not predicted. Despite these findings, the numerical model performed better than a previous model developed by the investigators. It was proposed that differences between the present numerical model and experiment stemmed from numerical underprediction of fuel-air turbulent mixing, and this resulted in underprediction of heat release.

20503 稠密炉心内3次元気泡流構造に関する大規模シミュレーション(大規模数値解析(1),OS11 大規模数値解析)

In order to predict the water-vapor two-phase flow structure in a fuel bundle of an advanced light water reactor, a large-scale numerical simulation was carried out using a newly developed two-phase flow analysis code and a highly parallel vector supercomputer. Conventional analysis methods with a two-fluid model need composition equations and empirical correlations based on the experimental data. Therefore, it is difficult to obtain high prediction accuracy when experimental data are nothing. Then, a new two-phase flow analysis method based on the latest computational science was proposed. This paper describes the predicted bubbly flow dynamics in three-dimensional minichannels and the predicted void fractions in the simulated tight-lattice fuel channels. Regarding the coalescence and fragmentation of bubbles the useful knowledge was obtained, and also the high prospect was acquired on the possibility of development of the thermal design procedure of the advanced nuclear reactors with large-scale simulations.

Numerical investigation of the flow front behaviour in the co-injection moulding process

This paper presents a three-dimensional (3D) solution algorithm for solving the sequential co-injection moulding process. The flow of skin and core materials inside a rectangular cavity is investigated both numerically and experimentally. A 3D finite element flow analysis code is used to solve the governing equations of the non-isothermal sequential co-injection moulding. The predicted flow front behaviour is compared to the experimental observations for various skin/core volume ratio, injection speed, injection temperature, and core injection delay. Simulation results are in good agreement with experimental data and indicate correctly the trends in solution change when processing parameters are changing. Solutions are also shown for the filling of a spiral-flow mould. The numerical approach is shown to predict the core expansion phase during which the flow front of core and skin materials advance together without breakthrough. Breakthrough phenomena is also predicted and the numerical solution is in good agreement with the experiment. Copyright © 2005 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

Flow Analysis for Single and Multi-Nozzle Jet Pump

Jet pumps, driven by a Primary-Loop Recirculation (PLR) Pump, have been widely used in Boiling Water Reactor (BWR) plants to recirculate the reactor core coolant. A jet pump consists of a driving nozzle, a bell-mouth, a throat and a diffuser. The improvement of the jet pump efficiency for BWR plants brings an economic advantage because it reduces the operating power cost of the PLR pump. In order to improve the efficiency of the BWR jet pump, a 1/5 scale jet pump test loop for BWR plant was used and intensive tests were conducted focusing on the types of driving nozzles and shapes of the throat. These test data were used for CFD flow analysis code verification. The analytical data showed good agreement with the test results. After the analytical model verification, improvement of jet pump efficiency was conducted. It was shown by the CFD analysis that the peak efficiency of the improved jet pump will be 36% with the tapered throat.

Numerical Analysis of a Water-Vapor Two-Phase Film Flow in a Narrow Coolant Channel with a Three-Dimensional Rectangular Rib

A reduced-moderation light water reactor (RMWR), which is studied by the Japan Atomic Energy Research Institute, needs to the volume ratio between the coolant and fuel less than 0.2, in order to achieve 1.1 or more high breeding ratios. The RMWR fuel assembly consists of many fuel rods with a diameter of around 10mm with the triangular tight-lattice configuration in the radial direction. A minimum gap width between adjacent fuel rods is about 1mm. Moreover, spacers are set to keep uniformly the gap width between fuel rods horizontally. These spacers are installed at a fixed interval to the flow direction in a reactor core. As a result of this, a complicated flow is formed around each spacer because of a large flow disturbance. Then, fundamental liquid film flow behavior in a narrow channel with a three-dimensional rectangular rib was analyzed numerically using a newly developed two-phase flow analysis code. From this study the following conclusions were derived: a wake behind the spacer rib takes place easier when the initial film thickness is short and then the gas velocity is higher than the liquid velocity; and, the liquid film thickness reduces with increasing the gas velocity.

狭隘流路内の大規模気泡流挙動に関する数値シミュレーション(S19-3 混相流の多次元ビジュアリゼーション(気液・気泡), S19 混相流の多次元ビジュアリゼーション)

In order to predict the water-vapor two-phase flow structure in a fuel bundle of an advanced light water reactor, a large-scale numerical simulation was carried out using a newly developed two-phase flow analysis code and a highly parallel vector supercomputer. Conventional analysis methods such as subchannel codes need composition equations based on the experimental data. In case that there are no experimental data for the advanced light water reactor, therefore, it is difficult to obtain high prediction accuracy. Then, a new analysis method using the large-scale direct numerical simulation of water-vapor two-phase flow was proposed. This paper, describes the predicted results of a large-scale bubbly flow in a narrow square duct. Regarding the mechanism of bubble coalescence and fragmentation the useful knowledge was obtained.

Three‐dimensional simulation of multi‐material injection molding: Application to gas‐assisted and co‐injection molding

AbstractThis paper presents an overview of the results obtained at the Industrial Materials Institute (IMI) on the numerical simulation of the gas‐assisted injection molding and co‐injection molding. For this work, the IMI's three‐dimensional (3D) finite element flow analysis code was used. Non‐Newtonian, non‐isothermal flow solutions are obtained by solving the momentum, mass and energy equations. Two additional transport equations are solved to track polymer/air and skin/core materials interfaces. Solutions are shown for different thin parts and then for thick three‐dimensional geometries. Different operating conditions are considered and the influence of various processing parameters is analyzed.

액체로켓 노즐의 열화학적 성능 해석

로켓 엔진 노즐의 설계에서 동결 유동 해법과 동일한 수치적 특성을 가지는 화학 평형 해석은 노즐의 열역학적 최대 성능을 예측하는 효율적인 설계 도구로 이용될 수 있다. 본 연구에서는 탄화수소 연료 로켓 엔진 설계를 위한 화학적 평형 유동 해석 코드를 개발하였다. 로켓 노즐을 통한 팽창과정에서 일어나는 화학 성분의 재결합 효과와 이에 수반하는 에너지 회복과 같은 열화학적 특징을 이해하기 위하여, KSR-III 로켓 노즐에 대하여 동결유동 해석 및 비평형 유동의 해석과 더불어 화학적 평형 유동 해석을 수행하였다. 유동 해석 결과에 기초한 KSR-III 엔진 성능 평가로부터 노즐에서의 열화학적 특징을 이해할 수 있었으며, 이와 더불어 열화학적인 효과를 고려할 때 출구 면적비를 줄여서 수정된 새로운 노즐 형상이 지상 추력을 증대시키기 위한 적절한 설계임을 확인할 수 있었다. For a design of rocket engine nozzle, chemical equilibrium analysis which shares the same numerical characteristics with frozen flow analysis can be used as an efficient design tool for predicting maximum thermodynamic performance of the nozzle. 10 this study, a chemical equilibrium flow analysis code was developed for the design of hydrocarbon fueled rocket engines. 10 oder to understand the thermochemical characteristics occurring in a nozzle through the expansion process, such as recombination of chemical components and the accompanying energy recovery, chemical equilibrium flow analysis was carried out for the KSR-III rocket engine nozzles together with frozen flow and non-equilibrium flow analyses. The performance evaluation based on the present KSR-III nozzle flow analyses has provided an understanding of the thermochemical process in the nozzle and additionally, it has confirmed that the newly designed nozzle shape modified to have a reduced exit area ratio is an adequate design for obtaining an increased ground thrust.

Numerical Analysis of Edge Over-coating in Continuous Hot-dip Galvanizing

The edge over-coating (EOC) developed near the edge of a galvanized steel strip is numerically analyzed. The 3-D flow field with alternating vortices in the region away from the strip edge is investigated and the distributions of mean impinging pressure and shear stress on the strip surface are obtained by using a commercial 3-D flow analysis code, STAR-CD. It was found that the appearance of alternating vortices causes the surface pressure to decrease gradually approaching the strip edge. The coating thickness is calculated by one integral analysis method of the boundary layer momentum equation. A sample calculation of a benchmark experiment on EOC problem shows that the present analysis method yields a reasonably accurate prediction of EOC for a given plant operating condition. And the result demonstrates theoretically that EOC can be effectively remedied by adjusting the distance of the 2-D air-knife nozzle and by installing a baffle plate parallel to the end of the steel strip.

C212 障害物を伴う平行平板流路内気液二相流の界面挙動に関する数値予測

Three-dimensional computations were carried out using a newly developed two-phase flow analysis code in order to analyze numerically free surface characteristics between water and vapor in narrow fuel channels with rectangular spacer ribs for reduced-moderation light water reactors. Calculations were conducted under isothermal condition. Major calculation parameters are water and vapor velocities at the channel inlet and initial thickness of water on the channel floor. The Liquid film flow behavior around one or two spacer ribs was predicted quantitatively.

Three-dimensional Numerical Modeling of Co-injection Molding

Abstract In this work, a three-dimensional finite element flow analysis code is used to solve sequential co-injection molding problems. Non-Newtonian, non-isothermal flow solutions are obtained by solving the momentum, mass and energy equations. Two additional transport equations are solved for tracking polymer/air and skin/core polymers interfaces. Solutions are shown for a center gated rectangular plate. The effect of varying the melt/mold temperature and the ratio between the skin and core materials is investigated. The solution obtained for the same skin and core materials is compared with those in which viscosities of core and skin materials are much different. Finally, the solution for the co-injection of a C-shaped plate is presented. The three-dimensional modeling of co-injection molding provides the complete shape of the core polymer as well as the skin polymer thickness at any location. This is a major improvement over the traditional mid-plane approach, which is unable to recover the material behavior in critical regions as near corners, obstacles, and changes in part thickness.

A study on an axial-type 2-D turbine blade shape for reducing the blade profile loss

Losses on the turbine consist of the mechanical loss, tip clearance loss, secondary flow loss and blade profile loss etc.,. More than 60 % of total losses on the turbine is generated by the two latter loss mechanisms. These losses are directly related with the reduction of turbine efficiency. In order to provide a new design methodology for reducing losses and increasing turbine efficiency, a two-dimensional axial-type turbine blade shape is modified by the optimization process with two-dimensional compressible flow analysis codes, which are validated by the experimental results on the VKI turbine blade. A turbine blade profile is selected at the mean radius of turbine rotor using on a heavy duty gas turbine, and optimized at the operating condition. Shape parameters, which are employed to change the blade shape, are applied as design variables in the optimization process. Aerodynamic, mechanical and geometric constraints are imposed to ensure that the optimized profile meets all engineering restrict conditions. The objective function is the pitchwise area averaged total pressure at the 30 % axial chord downstream from the trailing edge. 13 design variables are chosen for blade shape modification. A 10.8 % reduction of total pressure loss on the turbine rotor is achieved by this process, which is same as a more than 1 % total-to-total efficiency increase. The computed results are compared with those using 11 design variables, and show that optimized results depend heavily on the accuracy of blade design.

Verification for Flow Analysis Capability in the Model of Three-Dimensional Natural Convection with Simultaneous Spreading, Melting and Solidification for the Debris Coolability Analysis Module in the Severe Accident Analysis Code ‘SAMPSON’, (I)

The debris coolability analysis module in the severe accident analysis code ‘SAMPSON’ has been enhanced to predict more mechanistically the safety margin of present reactor pressure vessels in a severe accident. The module calculates debris three-dimensional natural convection with simultaneous spreading, melting and solidification using the ‘debris spreading-cooling model’ in combination with the temperature distribution of the vessel wall and it evaluates the wall failure. Debris spreading is solved by the free surface calculation method in which the height function is applied. The model makes possible a multiplex heat and mass transfer analysis with flow spearhead and melt front transportation for a single-phase flow analysis code through the resetting of two types of mesh attributions and re-arrangement of the pressure matrix at each time step. The results calculated with the present model are compared with the results from a water spreading experiment. The comparisons verify the model capability for predictions of debris flow in the spreading process. The module provides a good tool for prediction of the reactor safety margin in a severe accident through the three-dimensional natural convection analysis of debris with simultaneous spreading, melting and solidification.

Verification for Flow Analysis Capability in the Model of Three-Dimensional Natural Convection with Simultaneous Spreading, Melting and Solidification for the Debris Coolability Analysis Module in the Severe Accident Analysis Code 'SAMPSON', (I).

The debris coolability analysis module in the severe accident analysis code ‘SAMPSON’ has been enhanced to predict more mechanistically the safety margin of present reactor pressure vessels in a severe accident. The module calculates debris three-dimensional natural convection with simultaneous spreading, melting and solidification using the ‘debris spreading-cooling model’ in combination with the temperature distribution of the vessel wall and it evaluates the wall failure. Debris spreading is solved by the free surface calculation method in which the height function is applied. The model makes possible a multiplex heat and mass transfer analysis with flow spearhead and melt front transportation for a single-phase flow analysis code through the resetting of two types of mesh attributions and re-arrangement of the pressure matrix at each time step. The results calculated with the present model are compared with the results from a water spreading experiment. The comparisons verify the model capability for predictions of debris flow in the spreading process. The module provides a good tool for prediction of the reactor safety margin in a severe accident through the three-dimensional natural convection analysis of debris with simultaneous spreading, melting and solidification.

Tritium behavior in the Caisson, a simulated fusion reactor room

In order to confirm tritium confinement ability in the deuterium–tritium (DT) fusion reactor, intentional tritium release experiments have been started in a specially fabricated test stand called ‘Caisson’, at Tritium Process Laboratory in Japan Atomic Energy Research Institute. The Caisson is a stainless steel leak–tight vessel of 12 m 3, simulating a reactor room or a tritium handling room. In the first stage experiments, about 260 MBq of pure tritium was put into the Caisson under simulated constant ventilation of four times air exchanges per h. The tritium mixing and migration in the Caisson was investigated with tritium contamination measurement and detritiation behavior measurement. The experimental tritium migration and removal behavior was almost perfectly reproduced and could almost be simulated by a three-dimensional flow analysis code.

Predicted thermohydraulic performance of the ITER Central Solenoid Model Coil conductors

The Central Solenoid Model Coil (CSMC) of the International Thermonuclear Experimental Reactor (ITER) will be installed and tested in 1999-2000 in a test facility at the Japan Atomic Energy Research Institute (JAERI) in Japan. The expected cable performance is predicted based on the strand data on RRR, n-value, critical current density, hysteresis loss measured for each production batch, as well as AC loss characterization on full size conductor samples. Simulation of the high field layer conductor performance has been performed for operation at 4.5 K by a 1-D thermohydraulic flow analysis code which also includes elements of the cryoplant facility. The simulation results show that the temperature of the conductor after the operation rises up to 6.0 K from the initial temperature of 4.5 K due to ac losses of the conductor, and the pressure rises up to 0.64 MPa from the initial pressure of 0.3 MPa. Thus, the simulation can correlate the strand and conductor data base with the thermohydraulic behavior of the Model Coil, and the experiments in turn can validate the simulation.