• Communications of the Korean Mathematical Society
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• v.22 no.4
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• pp.587-596
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• 2007

In this paper, we study two-phase flow models. The chunk mix model of the two-phase flow equations is analyzed by a characteristic analysis. The model discussed herein has real characteristic values for all physically acceptable states and except for a set of measure zero has a complete set of characteristic vectors in state space.

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.161-173
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• 2009

This study analyzes especially drag and lift models recently developed for fluid-solid, fluid-fluid or liquid-liquid two-phase flows to understand their applicability on the computational fluid dynamics, CFD modeling of pulsatile blood flow. Virtual mass effect and the effect of red blood cells, RBCs aggregation on CFD modeling of blood flow are also shortly reviewed to recognize future tendencies in this field. Recent studies on two-phase flows are found as very useful to develop more powerful drag-lift models that reflect the effects of blood cell's shape, deformation, concentration, and aggregation.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.25-30
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• 1994

W-Ti-C-N based multiphase hard materials have been prepared from WC/TiN powder mixture. By sintering at and above 190$0^{\circ}C$, the two phases of powder mixture has transformed into intermixed W, W2C and Ti(C, N) phases. For the temperature range between 180$0^{\circ}C$ and 210$0^{\circ}C$, the sintered or hot pressed samples show maximum density and hardness. The seems that metallic W grains enhance the fracture toughness of materials. The wear resistance of the material is found to increase with increasing hardness.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.144-149
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• 2002

This paper presents the result of numerical simulation of particles trace following melted zinc movement with nitrogen gas injection. The code of the computational fluid dynamics for numerical analysis was performed using FLUENT related to CFD. As application model, there was applied Eulerian multiphase model for simulation of melted zinc movement at first and then was used stochastic tracking technique for particles trace secondarily. Numerical simulation results are shown that particles move to the same direction as the movement of melted zinc.

• 전기의세계
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• v.27 no.6
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• pp.63-68
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• 1978

To convert into multiphase from single phase are often necessary for industry field. In oder to convert of phase, phase shifted voltages are first buileded by single phase and then must combine with these voltages adequately. This paper aims at the description of the way of phase shift by means of turning on or turning off through natural commutation and forced commutation methods with firing angle of thyristor pating a role of switching controlled adequately. Experimental result of the Phase Shift with the Thyristors Utilized has been turned out to shift the phase to 60.deg., 90.deg., 120.deg., and other angles.

• Journal of Power Electronics
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• v.19 no.2
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• pp.344-352
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• 2019

To achieve high efficiency and reliability, multiphase interleaved converters with coupled inductors have been widely applied. In this paper, a coupled inductor design method for 2-phase interleaved boost converters is presented. A new area product equation is derived to select the proper core size. The wire size, number of turns and air gap length are also determined by using the proposed coupled inductor design method. Finally, the validity of the proposed coupled inductor design method is confirmed by simulation and experimental results obtained from a design example.

• Journal of Computational Design and Engineering
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• v.1 no.3
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• pp.173-186
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• 2014

The failure of a subsea production plant could induce fatal hazards and enormous loss to human lives, environments, and properties. Thus, for securing integrated design safety, core source technologies include subsea system integration that has high safety and reliability and a technique for the subsea flow assurance of subsea production plant and subsea pipeline network fluids. The evaluation of subsea flow assurance needs to be performed considering the performance of a subsea production plant, reservoir production characteristics, and the flow characteristics of multiphase fluids. A subsea production plant is installed in the deep sea, and thus is exposed to a high-pressure/ low-temperature environment. Accordingly, hydrates could be formed inside a subsea production plant or within a subsea pipeline network. These hydrates could induce serious damages by blocking the flow of subsea fluids. In this study, a simulation technology, which can visualize the system configuration of subsea production processes and can simulate stable flow of fluids, was introduced. Most existing subsea simulations have performed the analysis of dynamic behaviors for the installation of subsea facilities or the flow analysis of multiphase flow within pipes. The above studies occupy extensive research areas of the subsea field. In this study, with the goal of simulating the configuration of an entire deep sea production system compared to existing studies, a DES-based simulation technology, which can logically simulate oil production processes in the deep sea, was analyzed, and an implementation example of a simplified case was introduced.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.156-164
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• 2014

In a delay line type of a time-to-digital converter implemented in Field Programmable Gate Array, the timing accuracy decreases for a longer carry chain. In this paper, we propose a structure that has a multi-phase clock and a state machine to check metastability; this would reduce the required length of the carry chain with the same time resolution. To reduce the errors caused by the time difference in the four delay lines associated with a four-phase clock, the proposed TDC generates a single input pulse from four phase clocks and uses a single delay line. Moreover, the state machine is designed to find the phase clock that is used to generate the single input pulse and determine the metastable state without a synchronizer. With the measurement range of 1 ms, the measured resolution was 22 ps, and the non-linearity was 25 ps.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.535-543
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• 2015

Measurements of multiphase flows containing bubbles have been limited because most existing methods target one phase flows. Especially, multiphase flows with a high void ratio have been rarely successful in measurements due to the sudden change of density and thick interfaces between air and water. This study introduces two methods that are capable of measuring flow fields regardless of bubble void ratio, named bubble image velocimetry and bundle fiber optic flow meter. The calculation of the depth of field is suggested to reduce and estimate errors by perspective image velocimetry. The bundle fiber optic flow meter is designed to increase a measurement rate using many optical fibers with a thin diameter. The two methods measured bubble plumes to test reliability and the velocity measurements show good agreement. In addition a hydraulic jump, one of the multiple flows in rivers was measured to test applicability of the methods.