• Coupled systems mechanics
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• v.3 no.1
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• pp.53-71
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• 2014

Accurate prognoses of the durability of concrete structures require a detailed description of the continuously running aging processes and a consideration of the complete load history. Therefore, in the framework of continuous porous media mechanics a model is developed, which allows a detailed analysis of the most important aging processes of concrete as well as a flexible coupling of different processes. An overview of the prediction model and the balance equations is given. The material dependent model equations, the consequences of coupling different processes and the solution scheme are discussed. In two case studies the aging of concrete due to hydration and chloride penetration are presented, which illustrate the capabilities and the characteristics of the developed model.

• Journal of the Korean GEO-environmental Society
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• v.18 no.2
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• pp.53-58
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• 2017

In this paper, we propose a new method to debond between mixed finite elements for porous media in ABAQUS (2014). ABAQUS just provides debonding algorithm for the u-p model using cohesive elements in standard version. However, this approach has a drawback that it is hard to simulate complex debonding problems like element separation, rigid body motion, and contact between separated elements in standard version. ABAQUS-explicit can resolve these complex problems, but cohesive elements for the u-p model cannot be applied. We introduce a new algorithm for debonding for porous media instead of using cohesive elements. In this method, subroutines VUMAT to apply constitutive models and VDISP to separate elements in ABAQUS are used to simulate debonding problems. In addition, a simple 2-D example is demonstrated in the ABAQUS-explicit solver.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.266-271
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• 2001

Buoyancy-driven natural convection is analysed by employing a linear stability theory in hori-zontal porous media with net through flow. Darcy's law is used to model the flow characteristics in porous media. Bated on the results of linear stability analysis, a heat transfer correlation was obtained by employing weakly nonlinear analysis. As the net through flow increases, the system becomes more stable and the effect of the Darcy-Rayleigh number on the Nusselt number decreases.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.213-213
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• 2011

본 논문에서 연구하고자 하는 팬은 대형 차량용 라디에이터 냉각팬으로써 수치해석을 통한 일반적인 팬의 성능 평가시 팬과 쉬라우드의 형상만을 이용하여 시뮬레이션 하지만 라디에이터를 거쳐 공기가 유입되는 실제 현상에 좀 더 가깝게 모사하고자 라디에이터의 압력 부하를 고려한 시뮬레이션을 수행하였고 기존 해석 결과와 비교하였다. 연구된 냉각팬은 쉬라우드의 전방에 라디에이터가 설치되며 라디에이터를 통하여 공기가 유입되기 때문에 라디에이터의 압력 부하에 따라 팬 성능에 영향을 준다. 라디에이터의 압력 부하 성능을 모사하기 위하여 쉬라우드 입구에 박스 형태로 라디에이터의 외부 크기를 모델링 한 후 수치해석 시 porous media model을 사용하여 풍속에 따른 압력 강하 곡선을 적용하였다. 수치해석에서 porous media model을 적용할 경우 실제적인 형상 모델링 없이도 실험으로부터 도출한 성능곡선을 조건으로 입력하여 실제 현상에 가까운 시뮬레이션을 할 수 있다. 그리고 팬 날개수 증가에 따른 해석을 수행하여, 날개수 변경에 따른 성능개선의 여지를 확인 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.164-169
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• 1986

Walsh analysis is applied to the numerical specification of the volume distribution which is the key parameter in the formulation of the constitutive equations of heterogeneous media, indicating the geometrical state of the mixture. An example of two-dimensional volume distribution, its approximation, and the Walsh correlation coefficients are presented and the change of the information distribution in the operations is investigated. The phenomena of information concentration upon the large-scale Walsh coefficients are applied to the volumetric response of porous slids, clarifying the validity of the spherical-model calculation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.422-432
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• 2001

An analytical characterization is presented on the transient heat transfer by an oscillating flow through a porous slab. Based on a two-equation model, analytic solutions are obtained for both the fluid and solid temperature variations. Two parameters are identified as the Stanton number for the internal heat exchange and the ratio of the thermal capacities between the solid and fluid phases. The heat transfer characteristics are shown to be classified into four regimes according to the two parameters and physical interpretation is presented on the particular heat transfer processes within each regime. In addition, the condition for the local thermal equilibrium between the phases is examined and the relevant criterion is suggested.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.209-210
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• 2004

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.140-150
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• 1997

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.244-251
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• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.

• Journal of the Korean Solar Energy Society
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• v.30 no.1
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• pp.34-41
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• 2010

Gas hydrates are solid solutions when water molecules are linked through hydrogen bonding and create host lattice cavities that can enclose many kinds of guest(gas) molecules. There are plenty of methane(gas) hydrate in the earth and distributed widely at offshore and permafrost. Several schemes, to produce methane hydrates, have been studied. In this study, depressurization method has been utilized for the numerical model due to it's simplicity and effectiveness. IMPES method has been used for numerical analysis to get the saturation and velocity profile of each phase and pressure profile, velocity of dissociation front progress and the quantity of produced gas. The values calculated for the sample length of 10m, show that methane hydrates has been dissolved completely in approximately 223 minutes and the velocity of dissociation front progress is 3.95㎝ per minute. The volume ratio of the produced gas in the porous media is found to be about 50%. Analysing the saturation profile and the velocity profile from the numerical results, the permeability of each phase in porous media is considered to be the most important factor in the two phase flow propagation. Consequently, permeability strongly influences the productivity of gas in porous media for methane hydrates.