• 한국전산유체공학회지
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• 제14권2호
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• pp.68-76
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• 2009

The sloshing tank causes the instability of the fluid flows and the fluctuation of the impact pressure by the liquid on the tank. These flow characteristics inside the sloshing tank can generate the uncomfortable sloshing noise. In the present study, a numerical analysis for the reduction of a fuel tank sloshing noise was performed. To simulate the flow characteristics in a sloshing tank with partially filled liquid, a VOF method was used for interfacial flows by applying a momentum source term for the sloshing motion in a non-inertial reference frame. This numerical method was verified by comparing its results with the available experimental data. For the reduction of the sloshing noise, the horizontal and vertical baffles and porous media inside a sloshing tank were considered and numerically analyzed in the present study. For various installations of these baffles and porous media, the characteristics of the liquid behavior in the sloshing tank were obtained along with the impact pressure on the wall and the height of the free surface along the wall. These basic results can be used for the design of the actual vehicular fuel tank with the reduced sloshing noise.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.241-246
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• 2000

Gas hydrates are solid solutions when water molecules are linked through hydrogen bondin create host lattice cavities that can enclose a large variety of guest gas molecules. The natural hydrate crystal may exist at low temperature above the normal freezing point of water and pressure greater than about 30 bars. A lot of quantities of natural gas hydrates exists in the ear many production schemes are being studied. In the present investigation, depressurization method considered to predict the production of gas and the simulation of the two phase flow - gas and - in porous media is being carried out. The simulation show about the fluid flow in porous have a variety of applications in industry. Results provide the appearance of gas and water prod the pressure profile, the saturation of gas/ water/ hydrates profiles and the location of the pl front.

• 연구논문집
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• 통권23호
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• pp.5-13
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• 1993

The present work deals with the theoretical prediction of static & dynamic characteristic of annular type externally pressurized thrust air bearings with metal-sintered porous media. For the evaluation of surface loading effect by machining, it is assumed that the flow at the porous surface is dominant and which is equivalent to the flow through orifice. Finite different method with over-relaxation method is used to solve the numerical problems. The influences of radius ratio, supply pressure and squeeze number on performances are investigated, as the results. The results of this study can be used to predict the optimal running condition and stable realm of porous bearings.

• 환경영향평가
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• 제18권2호
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• pp.79-87
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• 2009

This study was performed for the application of porous concrete blocks and aquatic plants for the water purification in small urban stream. This study investigated the ability of water purification according to various environments, algae and aquatic plants. When the porous concrete was used as contact media, the average removal efficiencies of SS, BOD and COD were 85~95%, 50~60% and 65~75%, respectively. Also, when the porous concrete and aquatic plants was used the average removal efficiency of SS, BOD and COD were 90~95%, 60~70% and 70~80%, respectively. As the results, average removal efficiency of total nitrogen, at the condition of the porous concrete and aquatic plants, was about 40-50%, then, that of total phosphorus was about 60-70%.

• 한국수자원학회논문집
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• 제31권4호
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• pp.459-467
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• 1998

유사매질개념에 의하여 비균질 다공성 매질을 설명할 수 있는 기존의 방법은 미시 밀러 상사(Mis), 거시 밀러 상사(MaS)와 웨릭 상사(WS)로 나눌 수 있고, 그들간의 관계는 MiS ⊂ MaS⊂ WS(⊂: subset)임을 알 수 있었다. 본 연구에서 제안한 방법은 WS에서 축적변수 $\alpha$=w 로 가정하고 함수량을 포화도 대신 유효포화도로 축적한 것이다. 이 방법은 검사해석의 관점에서 일반성이 결여되지 않고, 축적변수 $\alpha$만으로 비균질 매질을 설명할 수 있다. 즉 =1($\alpha$의 평균값)인 매질은 비균질 매질에 상응하는 등가매질을 의미하고, $\alpha$의 표준편차는 다공성 매질의 비균질 정도를 설명한다. $\alpha$>1인 매질의 특수계수는 등가매질의 투수계수보다 크며 또한 유효함수량은 $\alpha$>1인 매질에서 크게 나타난다. 이와같은 $\alpha$의 성질을 이용하여 가상적인 여직 1차원 비균질 다공성 매질을 난수 발생기법으로 생성하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권3호
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• pp.243-259
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• 2016

The Richards equation for water movement in unsaturated soil is highly nonlinear partial differential equations which are not solvable analytically unless unrealistic and oversimplifying assumptions are made regarding the attributes, dynamics, and properties of the physical systems. Therefore, conventionally, numerical solutions are the only feasible procedures to model flow in partially saturated porous media. The standard Finite element numerical technique is usually coupled with an Euler time discretizations scheme. Except for the fully explicit forward method, any other Euler time-marching algorithm generates nonlinear algebraic equations which should be solved using iterative procedures such as Newton and Picard iterations. In this study, lumped mass and distributed mass in the frame of Picard and Newton iterative techniques were evaluated to determine the most efficient method to solve the Richards equation with finite element model. The accuracy and computational efficiency of the scheme and of the Picard and Newton models are assessed for three test problems simulating one-dimensional flow processes in unsaturated porous media. Results demonstrated that, the conventional mass distributed finite element method suffers from numerical oscillations at the wetting front, especially for very dry initial conditions. Even though small mesh sizes are applied for all the test problems, it is shown that the traditional mass-distributed scheme can still generate an incorrect response due to the highly nonlinear properties of water flow in unsaturated soil and cause numerical oscillation. On the other hand, non oscillatory solutions are obtained and non-physics solutions for these problems are evaded by using the mass-lumped finite element method.

• 설비공학논문집
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• 제6권4호
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• pp.399-405
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• 1994

Beacuse of the energy resources exhaustion, the aggravating environmental air pollution and the smoke phenomena etc., the importance of clean gas fuel compared with liquid fuel is highly considered in recent years. The combustion system which consists of porous media is actively studied as a new method for solving above problems. Therefore, excess enthalpy combustion using porous media was interested by many researchers and investigated through numerical and experimental analysis. In this study, the simplified combustor has the unique combustion characteristics of mixture gas preheated effect using radiative and convective heat energy by changing the flow passage of unburned gas with solenoid valves and has the intensive excess enthalpy phenomena As the result of according to reduce equivalence ratio, flame temperature was remarkably higher than adiabatic flame temperature. This show the ability of super-lean combustion.

• Wind and Structures
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• 제9권2호
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• pp.147-158
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• 2006

The purpose of this paper is to find a more accurate method to evaluate pedestrian wind by computational fluid dynamics approach. Previous computational fluid dynamics studies of wind environmental problems were mostly performed by simplified models, which only use simple geometric shapes, such as cubes and cylinders, to represent buildings and structures. However, to have more accurate and complete evaluation results, various shapes of blocking objects, such as trees, should also be taken into consideration. The aerodynamic effects of these various shapes of objects can decrease wind velocity and increase turbulence intensity. Previous studies simply omitted the errors generated from these various shapes of blocking objects. Adding real geometrical trees to the numerical models makes the calculating domain of CFD very complicated due to geometry generation and grid meshing problems. In this case the function of Porous Media Condition can solve the problem by adding trees into numerical models without increasing the mesh grids. The comparison results between numerical and wind tunnel model are close if the parameters of porous media condition are well adjusted.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.703-710
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• 2003

In the sub-surface environments, detection of the movement of contaminant substances and recharge of groundwater by rainfall are very important factors which contain porosity and effective porosity of porous media. In this paper, the applicability of permittivity methods and proposed dielectric mixing models (DDMs) are discussed. This study showed that the ratio of effective porosity to porosity of Toyoura and River sands were 0.856 and 0.843. From the relationships between the relative porosity and effective porosity, all measured values can be confirmed to outside the range to about 0.800 for Toyoura and River sands under all experiments by FDR and FDR-V systems. In the study, this permittivity equipment can be considered to be good enough to measure determining the physical parameters of saturated soils. Consequently, this permittivity method can be contributed to estimate a porosity and effective porosity of saturated porous media because it is easy and instantaneous than previous in-situ methods.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1668-1678
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• 1997

Numerical analyses were performed to investigate the characteristics of regenerator in oscillating flow by using moving boundary method and Darcy model. In this work, periodic adiabatic boundary condition was suggested as the boundary condition of adiabatic part so that the effects of the thermal inertia of the wall could be considered. In carrying out numerical analyses, two models were applied and compared. One called isotropic model has the same thermal conductivity in radial and axial directions within a porous media. The other called aeolotropic model has different conductivity in each directions. Isotropic model could not show the advantage of energy reduction which needs to maintain constant wall temperature difference between heater and cooler. But aeolotropic model could simulate the reduction of energy consumption.