Mold filling simulation for the die casting process is a very important aspect of CAE analysis to predict the molten metal flow pattern and to optimize the die design for the process. One of the effective means to imp...
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Mold filling simulation for the die casting process is a very important aspect of CAE analysis to predict the molten metal flow pattern and to optimize the die design for the process. One of the effective means to improve the computational efficiency and scale is the implementation of parallel computation technique. Based on analysis of the mathematical model and the computational algorithm for the mold filling simulation, some computational parameters that influence the efficiency in the SOLA-VOF algorithm were summarized by numerical experiments. A parallel search algorithm was developed and implemented on a cluster computation platform to optimize the efficiency parameters by searching the most efficient parameters dynamically. The verifications on the mold filling simulation of practical die casting components show that the optimization of efficiency parameters can greatly improve the computational efficiency to some extent while maintaining the computational accuracy.
Solving simulated moving bed (SMB) chromatography models requires fast and accurate numerical techniques, since their system size computed is large due to multi-columns and multi-components, in addition the axial solu...
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Solving simulated moving bed (SMB) chromatography models requires fast and accurate numerical techniques, since their system size computed is large due to multi-columns and multi-components, in addition the axial solution profiles contain steep moving fronts. The space-time conservation element/solution element (CE/SE) method addressed in this study enforces both local and global flux conservation in space and time, and uses a simple stencil structure (two points at the previous time level and one point at the present time level) on staggered space-time grids. Thus, accurate and computationally efficient numerical solutions are obtained. Stable solutions are guaranteed if the Courant-Friedrichs-Lewy (CFL) condition is satisfied. The boundary condition and recycle flow treatments are much simpler than for the time integrator in the framework of the method of lines. Applying the CE/SE method for SMB chromatographic problems, non-dissipative and accurate solutions are obtained and fast calculation is achieved in this study. The effects of two-computational parameters (CFL number and mesh stepsize) on the numerical solution are examined, illustrating two SMB processes whose Peclet and Stanton numbers are different. It is shown that the CFL number affects little the numerical solution under the relatively high Peclet number and low Stanton number but a small mesh stepsize is required to enhance accuracy. As the Peclet number decreases and the Stanton number increases, a lower CFL number is preferable and larger mesh stepsize is permitted. In the case study of the SMB adsorption problems, a large CFL number and sufficient number of mesh points (or small mesh stepsize) are desirable to reduce the calculation time and increase accuracy. (C) 2004 Elsevier Ltd. All rights reserved.
The damping-solvent extraction method for the analysis of unbounded visco-elastic media is evaluated numerically in the frequency domain in order to investigate the influence of the computational parameters-domain siz...
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The damping-solvent extraction method for the analysis of unbounded visco-elastic media is evaluated numerically in the frequency domain in order to investigate the influence of the computational parameters-domain size, amount of artificial damping, and mesh density-on the accuracy of results. An analytical estimate of this influence is presented, and specific questions regarding the influence of the parameters on the results are answered using the analytical estimate and numerical results for two classical problems: the rigid strip and rigid disc footings on a visco-elastic half-space with constant hysteretic material damping. As the domain size in increased, the results become more accurate only at lower frequencies, but are essentially unaffected at higher frequencies. Choosing the domain size to ensure that the static stiffness is computed accurately leads to an unnecessarily large domain for analysis at higher frequencies. The results improve by increasing artificial damping but at a slower rate as the total (material plus artificial) damping ratio zeta(t) gets closer to 0.866. However, the results do not deteriorate significantly for the larger amounts of artificial damping, suggesting that zeta(t) approximate to 0.6 is appropriate;a larger value is not likely to influence the accuracy of results. Presented results do not support the earlier suggestion that similar accuracy can be achieved by a large bounded domain with small damping or by a small domain with larger damping. Copyright (C) 2002 John Wiley Sons, Ltd.
As a part of the study to expand the computational region of SPEEDI (System for Prediction of Environmental Emergency Dose Information), a mass-consistent wind field model developed for the local or mesoscale wind fie...
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As a part of the study to expand the computational region of SPEEDI (System for Prediction of Environmental Emergency Dose Information), a mass-consistent wind field model developed for the local or mesoscale wind field was improved for the calculation of synoptic wind field. The major modification is the consideration of earth's curvature. The values of computational parameter were reexamined. This model was applied to the calculation of three-dimensional wind fields over Europe in the case of Chernobyl accident. The calculated horizontal wind fields agreed well with patterns of surface pressure and 850 mb geopotential height. The cyclonic winds around low pressure regions and the anticyclonic winds around high pressure regions were successfully computed by the model. The distribution pattern of calculated vertical wind roughly correlated with the surface weather chart.
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