• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.698-703
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• 2017

Bubble flow characteristics in fluidized beds were analyzed by CPFD simulation. A fluidized bed, which had the size of $0.3m-ID{\times}2.4m-high$, was modeled by commercial CPFD $Barracuda^{(R)}$. Properties of bed material were $d_p=150{\mu}m$, ${\rho}_p=2,330kg/m^3$, and $U_{mf}=0.02m/s$. Gas was uniformly distributed and the range of superficial gas velocity was 0.07 to 0.16 m/s. Two other geometries were modeled. The first was a three-dimensional model, and the other was a two-dimensional model of $0.01m{\times}0.3m{\times}2.4m$. Bubble size and rising velocity were simulated by axial and radial position according to superficial gas velocity. In the case of three-dimensional model, simulated bubble rising velocity was different from correlations, because there was zigzag motion in bubble flow, and bubble detection was duplicated. To exclude zigzag motion of bubble flow, bubble rising velocity was simulated in the two-dimensional model and compared to the result from three-dimensional model.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.156-164
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocity and temperature fields during rheology forming process, the earth governing equation correspondent to the liquid and solid region are adapted. Therefore, each numerical models considering the solid and liquid region existing within the semi-solid material have been developed to predict the deflect of rheology forming gnarls. The Arbitrary Boundary Maker And Cell (ABMAC) method is employed to solve the two-phase flow model of the Navier-Stokes equation. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity. The liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1554-1561
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• 2005

Geotextiles form one of the two largest groups of geosynthetics and it is consisted two major types of synthetic material (Woven, Non-woven). The functions of geotextiles are separation, reinforcement, filtration, drainage and as a moisture barrier. Within these functions, however, there are a large number of applications or use areas. Although the many research scholar and engineer developed and established the design criteria and construction methodology of geosynthetics filter layer, because the lack of suitable design terminology and uncertainty of long term durability, sustainable research still needed for optimum design methodology to the complicate field conditions. Especially, more intensive research needed about under the cyclic flow condition and fine silty sand base material. In this paper, the filter model test performed under cyclic flow with various boundary conditions (period and frequency of cyclic flow, types of geosynthetic filter material, surcharge etc.).

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.25-32
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• 2002

In order to control of water quality in Jeju harbor, variation of physical oceanographic environments was estimated using material cycle model. It is composed of the three-dimensional hydrodynamic model for the simulation at water flow and material cycle model for the simulation of water quality. The three dimensional hydrodynamic model simulation of the circulation and mixing in Jeju Harbor has been conducted forced by Sanzi River Discharge, Tidal elevation, wind and Solar heat in case of August and November, 2000 and February and May, 2001, respectively. The results of numerical model and observation show that the model can produce realistic results of current in the harbor. The monthly variation of velocity pattern are not so much changed are found In Jeju Harbor. The residual current was forced by temperature, salinity, density, wind and tidal current. The residual current of August, 2000 are the strongest among four month. It can be explained that the density effect can be important role in residual current at Jeju Harbor. As the results of salinity distribution simulation, very low concentration of all levels were simulated in August, 2000. The flowrate of Sanzi river was investigated 77,760 ㎥ /d in August, 2000. Therefore, pollutant loadings from Sanzi river should be considered for water quality management in Jeiu harbor.

• Computers and Concrete
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• v.4 no.2
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• pp.101-117
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• 2007

A new model predicting the nonlinear basic creep behaviour of concrete structures subjected to high multi-axial stresses is proposed. It combines a model based on the thermodynamic framework of the elasto-plastic continuum damage theory for time-independent material behaviour and a rheological model describing phenomenologically the long-term delayed deformation. Strength increase due to ageing is regarded. The general 3D solution for the creep theory is derived from a rate-type form of the uniaxial formulation by the assumption of associated creep flow and a theorem of energy equivalence. The model is able to reproduce linear primary creep as well as secondary and tertiary creep stages under high compressive stresses. For concrete in tension a simple viscoelastic formulation is applied. The material law is then incorporated into a finite element solution procedure for analysis of reinforced concrete structures. Numerical examples of uniaxial creep tests and concrete members show excellent agreement with experimental results.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.102-110
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• 1997

A two dimensional shallow-water flow around a cavity driven by a sinusoidally oscillating external flow was studied numerically with an Ekman pumping model. A container model of "T" shape was constructed in the numerical computation for comparison with the experimental observation. The material transport in the external region is in good agreement with the experimentally recorded particle trajectories. It turns out that two large coherent vortices situated in the exterior region of the cavity are responsible for clockwise and counterclockwise drift motions, in large scale, of particles. The Ekman pumping model suggested in this study was found to be satisfactory.isfactory.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.584-589
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• 2008

It is known that slab thermal storage which uses concrete slab as thermal material is effective in the load leveling and using the nighttime electric power. The temperature distribution is not constant in plenum in thermal storage time by beams, ducts such as several factor. It is considered that this fact will effect on efficiency of thermal storage and indoor thermal environment. The purpose of this paper is to examine the thermal environment inside plenum. A macro model was made for the analysis of indoor thermal environment as the first step. The flow rate distribution and temperature distribution of object room model was examined by use of basic equations such as airflow by the pressure difference between unit cells, heat flow by air and heat transfer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.828-834
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• 1997

The knowledge of material stress-strain behavior is an essential requirement for design and analysis of deformation processes. Empirical stress-strain relationship and constitutive equations describing material behavior during deformation are being widely used, despite suffering some drawbacks in terms of ease of development, accuracy and speed. In the present study, back-propagation neural networks are used to model and predict the flow stresses of a HSLA steel under conditions of constant strain, strain rate and temperature. The performance of the network model is comparedto those of statistical models on rate equations. Well-trained network model provides fast and accurate results, making it superior to statistical models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.107-110
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• 2003

We have proposed a model to describe the current-voltage characteristics of fabricated devices using the Biot-Savart's law in order to develop superconducting flux flow transistors, The measured and calculated values, including induced voltage, transresistance and current gain were investigated in relation to the parallel flow of the vortices in a single microbridge. The predictions agreed very well with measured results.