• 대한기계학회논문집B
• /
• 제34권1호
• /
• pp.9-18
• /
• 2010

2 상 유동 압력강하에 대한 모델은 균질유동모델과 분리유동모델 두 가지가 있다. 많은 선행 연구자들은 마이크로채널에서의 2 상 유동 압력강하에 대한 상관식을 제시하였고, 대부분은 분리유동모델에 해당하는 Lockhart- $Martinelli^{(27)}$의 수정된 상관식에 기초하고 있다. 본 연구에서는 사각 마이크로채널에서의 압력강하에 대한 연구를 위해서 액상의 물과 기상의 질소를 사용하여 사각 마이크로채널에서의 실험을 수행하였다. 2 상 마찰 압력강하는 2 상 유동양식에 큰 연관성을 가지고 있는 결과를 확인할 수 있었다. 6 가지의 2 상 점성 모델을 포함한 균질유동 모델 ($Owen^{(21)}$'s, $MacAdams^{(22)}$'s, Cicchitti et ${al.}^{(23)}$'s, ${al.,}^{(24)}$ Beattie and ${Whalley,}^{(25)}$ Lin et ${al.}^{(26)}$)과 6 가지의 분리유동 모델 (Lockhart and $Martinelli,^{(27)}$ ${Chisholm,}^{(31)}$ Zhang et ${al.,}^{(15)}$ Lee and ${Lee,}^{(5)}$ Moriyama and ${Inue,}^{(4)}$ Qu and $Mudawar^{(8)}$)에 대한 평가를 실험결과와 비교를 통해 수행하였다. 가장 우수한 2 상 점성 모델은 Beattie and Whalley 의 모델이었고, 가장 우수한 분리유동 모델은 Qu and Mudawar 의 상관식이였다. 균질유동모델과 분리유동모델 모두에 대해서 2 상 유동양식에 종속성을 나타내었다. 그러므로, 본 연구에서는 2 상 유동 양식에 기초한 새로운 상관식을 균질유동모델과 분리유동모델에 대해 각각을 제시하였다.

• Geomechanics and Engineering
• /
• 제31권2호
• /
• pp.159-166
• /
• 2022

The model of two-dimensional plane waves is analyzed in a micropolar-thermoelastic solid with microtemperatures in the context of the three-phase-lag model, dual-phase-lag model, and the Green-Naghdi theory of type III. Harmonic wave analysis is used to hold the solution to the problem. Numerical results of the physical fields are visualized to show the effects of the gravity field, magnetic field, and viscosity. The expression for the field variables is obtained generally and represented graphically for a particular medium.

• 대한기계학회논문집
• /
• 제9권6호
• /
• pp.714-724
• /
• 1985

본 논문에서는 입자가 부상된 2상유동의 해석에서 여러유동조건의 유동을 공 통적으로 해석할 수 있고 또 유동의 난류구조를 규명할 수 있도록 하기 위해서 2-방정 식 난류모델을 적용하였고 또 지배방정식들 속에 나타나는 1유체와 2유체의 2차 상관 관계들을 모형화 할 때 Taweel and Landau의 스펙트럼 이론을 확장발전시켜 적용하였 다.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
• /
• pp.537-542
• /
• 1996

In the present work the influence of various physical parameters on the two-phase flow behavior in a self-heated porous medium has been studied using a numerical model, that is, the effects of heat generation rate, of porosity, of particle size, and of system pressure on the dryout process. To analyze the effect of these parameters, the variation of both liquid volumetric fraction and liquid axial velocity is evaluated at the steady state or at the onset of a first boiled-out region. The analysis of computational results indicate that a qualitative tendency exists between the parameters such as heat generation rate, porosity, effective particle diameter and the temporal development of the liquid volumetric fraction field up to dryout. In addition to these parameters, a variation of fluid properties such as phase density, phase viscosity due to a change of system pressure can be used for gaining insight into the nature of two-phase flow behavior up to dryout.

• Nuclear Engineering and Technology
• /
• 제45권1호
• /
• pp.21-28
• /
• 2013

The flow and heat transfer characteristics of the ex-vessel core melt (corium) were investigated using a commercial CFD code along with the experimental data on the spreading of corium available in the literature (VULCANO VE-U7 test). In the numerical simulation of the unsteady two-phase flow, the volume-of-fluid model was applied for the spreading and interfacial surface formation of corium with the surrounding air. The effects of the key parameters were evaluated for the corium spreading, including the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The results showed a reasonable trend of corium progression influenced by the changes in the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The modeling of the viscosity appropriate for corium and the radiative heat transfer was critical, since the front progression and temperature profiles were strongly dependent on the models. Further development is required for the code to consider the formation of crust on the surfaces of corium and the interaction with the substrate.

• 대한기계학회논문집B
• /
• 제26권6호
• /
• pp.772-778
• /
• 2002

A numerical analysis of turbulent gas-particle two-phase flow is performed in conjunction with the experiments of Fackrell ＆ Robins and Raupach & Legg that considered ground-level source and/or elevated source flat plate flow. K-$\omega$ turbulence model is used in order to analyze fully turbulent flow field and the concentration equation with settling velocity is adopted for the concentration field. The model of Einstein and Chien is applied that couples the velocity field and the concentration field. Turbulent eddy viscosity is re-evaluated in this model. The present numerical results have good agreement between the simulation and the experimental data for the mean flow velocities and particle concentrations. While the previous study shows about 27% error in the vicinity of the source of particle concentration, the .present study allows about 14% error. A new turbulent gas-particle flow model developed by this study is able to cut down error by 13% at a near source.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.2005-2011
• /
• 2003

Introducing the interfacial pressure jump terms based on the surface tension into the momentum equations of two-phase two-fluid model, the system of governing equations is turned mathematically into the hyperbolic system. The eigenvalues of the equation system become always real representing the void wave and the pressure wave propagation speeds as shown in the previous manuscript. To solve the interfacial pressure jump terms with void fraction gradients implicitly, the conventional semi-implicit method should be modified as an intermediate iteration method for void fraction at fractional time step. This advanced semi-implicit method (ASIM) then becomes stable without conventional additive terms. As a consequence, including the interfacial pressure jump terms with the advanced semi-implicit method, the numerical solutions of typical two-phase problems can be more stable and sound than those calculated exclusively by using any other terms like virtual mass, or artificial viscosity.

• Korea-Australia Rheology Journal
• /
• 제13권4호
• /
• pp.189-196
• /
• 2001

The phase morphology is an important factor in the rheology of immiscible polymer blends. Through its size and shape, the interface between the two phases determines how the components and the interface itself will contribute to the global stresses. Rheological measurements have been used successfully in the past to probe the morphological changes in model blends, particularly for dilute systems. For more concentrated blends only a limited amount of systematic rheological data is available. Here, viscosities and first normal stress differences are presented for a system with nearly Newtonian components, the whole concentration range is covered. The constituent polymers are PDMS and PIB, their viscosity ratio can be changed by varying the temperature. The data reported here have been obtained at 287 K where the viscosities of the two components are identical. By means of relaxation experiments the measured stresses are decomposed into component and interfacial contributions. The concentration dependence is quite different for the two types of contribution. Except for the component contributions to the shear stresses there is no clear indication of the phase inversion. Plotting either the interfacial shear or normal stresses as a function of composition produces in some cases two maxima. The relaxation times of these stresses display a similar concentration dependence. Although the components have the same viscosity, the stress-component curves are not symmetrical with respect to the 50/50 blend. A slight elasticity of one of the components seems to be the cause of this effect. The data for the more concentrated blends at higher shear rates are associated with a fibrillar morphology.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1997년도 추계 학술대회논문집
• /
• pp.120-125
• /
• 1997

In the present work the influence of various physical parameters on the two-phase flow behavior in a self-heated porous medium has been studied using a numerical model, that is, the effects of heat generation rate, of porosity, of particle size, and of system pressure on the dryout process. To analyze the effect of these parameters, the variation of both liquid volumetric fraction (i.e., liquid saturation) and liquid axial velocity is evaluated at the steady state or at the onset of a first boiled-out region. The analysis of computational results indicate that a qualitative tendency exists between the parameters such as heat generation rate, porosity, effective particle diameter and the temporal development of the liquid volumetric fraction field up to dryout. In addition to these parameters, a variation of fluid properties such as phase density, phase viscosity due to a change of system pressure can be used for gaining insight into the nature of two-phase flow behavior up to dryout.

• 한국결정성장학회지
• /
• 제1권1호
• /
• pp.74-81
• /
• 1991

Czochralski 단결정 성장계에서 유체동의 표면 복사열전달을 고려하여 온도분포를 모사하였다. 복사열전달 고려시 표면요소들의 view factor를 고려하였다. 고-액의 2상은 고상에 가상적으로 매우 큰 점성을 부여하여 연속의 단상으로 처리하였으며 응고시 잠열은 반복열량 방출법을 개발하여 처리하였다. 본 연구에서 개발한 응고 모델을 증명하기 위하여 Ca 금속의 용융에 적용하여 실험결과와 비교한 결과 잘 맞는다는 것을 알아낸 후 본 모사 프로그램을 Cz계에서 Al금속의 단결정 성장에 적용하였다.