• 한국가스학회지
• /
• 제22권3호
• /
• pp.65-73
• /
• 2018

석탄층 메탄가스는 압력에 따라 비선형적인 탈착곡선을 보이므로 이를 고려하여 적절한 생산시스템이 구성되어야 한다. 석탄층 메탄가스 생산설비의 용량 및 규격은 시스템의 경계조건인 탄층 내 가스 유량과 압력조건에 의해 결정되며 이러한 특성을 분석하는 것은 가스 생산 증진을 위해 필수적이다. 본 연구를 위해 대표적인 미국 CBM 상용가스전인 San Juan 지역의 저류전산 모델을 구성하여 가스 유입방정식을 산출하였고, 이를 전체 생산시설의 경계조건으로 활용하였다. 또한 생산시설 내 가스 유량에 따른 압력감소의 영향을 분석하기 위해 생산설비 유동 분석시뮬레이터를 이용하여 노달분석을 수행하여 생산시설의 적정 규격 및 운영조건을 결정하였다. 이를 통해 석탄층 메탄가스 가스전의 최적 수송, 생산 및 포집시스템 설계 기준을 제시하였다.

• 대한조선학회논문집
• /
• 제53권5호
• /
• pp.388-399
• /
• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• 한국전산구조공학회논문집
• /
• 제25권4호
• /
• pp.293-300
• /
• 2012

본 논문에서는 직교이방성 적층평판에서의 균열생성 및 전파로 이루어진 층간분리해석을 다룬다. 기존의 p-유한요소가 가지고 있는 요소의 강건성을 균열진전해석에 적용하여, 균열진전시 모델링을 재구성하지 않고, 균열 선단부에 해당되는 꼭지점 모드의 위치만을 이동하도록 하여, 요소망을 단순화시켰다. 이와 같은 층간분리해석에 대해서 이 논문에서의 주요 목적은 다음 두 가지이다. 첫째, 적층복합 재료의 층간분리해석 시, 일반적인 유한요소 모델과 비교하여 매우 간단한 요소망을 가지는 모델을 제안하는 것이다. 모델의 타당성을 평가하기 위해 적층 복합재료로 구성된 이중 외팔보 해석을 통하여, 기존 참고문헌 값과의 비교를 수행하였다. 둘째, 제안된 모델을 내부균열을 갖는 적층평판의 층간분리해석에 적용하여 여러 가지 거동 양상에 대한 평가이다. 이와 같은 목적을 수행하기 위하여 로바토 형상함수를 이용한 완전층별요소가 고려되었으며, 선형탄성파괴역학에 기초한 3차원 가상균열닫힘법을 이용하여 에너지 방출률을 산정하였다.

• 한국수자원학회논문집
• /
• 제43권9호
• /
• pp.769-780
• /
• 2010

'위상적 평가'와 '수리학적 평가'를 통해 수요절점에서 필요한 수량을 필요한 압력으로 충분히 공급할 수 있는지의 여부를 정량화하고 이를 신뢰성의 산정을 위한 기준으로 사용하는 것은 대표적인 상수관망시스템의 신뢰성산정 방법이다. 하지만 '수리학적 평가'를 이용한 수요절점에서의 압력확보 여부를 신뢰성 산정에 사용한 기존의 연구들은 'Demand-Driven Analysis의 사용'과 '사용성의 미고려'라는 두 가지 측면에 있어서 문제가 있다. 또한 비정상상태인 상수관망시스템의 수리모의 적합한 Pressure-Driven Analysis를 이용한 연구들도 신뢰성 산정에 있어 가능공급량만을 고려하고 사용성을 고려하지 않아, Pressure-Driven Analysis의 장점이 효율적으로 사용되지 않은 단점이 있다. 본 연구에서는 기 개발 된 Pressure-Driven Analysis 모형인 HSPDA모형과, 거리척도 방법을 이용하여 수량과 수압을 동시에 고려하는 신뢰성 분석기법을 제안하였다. 제안된 기법을 상수관망에 적용하여 기존의 연구결과와 비교하였고 이를 바탕으로 수립 가능한 신뢰성 확보방안을 제시하였다.

• Nuclear Engineering and Technology
• /
• 제28권5호
• /
• pp.488-499
• /
• 1996

We have extended the source projection analytic nodal discrete ordinates method (SPANDOM) for more flexible applicability in analysis of hexagonal assembly cores. The method (SPANDOM-FH) does not invoke transverse integration but instead solves the discrete ordinates equation analytically after the source term is projected and represented in hybrid form of high-order polynomials and exponential functions. SPANDOM-FH which treats a hexagonal node as one node is applied to two fast reactor benchmark problems and compared with TWOHEX. The results of comparison indicate that the present method SPANDOM-FH predicts accurately $k_eff$ and flux distributions in hexagonal assembly cores. In addition, SPANDOM-FH gives the continuous two dimensional intranodal scalar flux distributions in a hexagonal node. The reentering models between TWOHEX and SPANDOM were also compared and it was confirmed that SPANDOM's model is more realistic. Through the results of benchmark problems, we conclude that SPANDOM-FH has the sufficient accuracy for the nuclear design of fast breeder reactor (FBR) cores with hexagonal assemblies.

• 대한전기학회논문지
• /
• 제35권11호
• /
• pp.479-486
• /
• 1986

It is necessary to consider a rotor movement in dynamic analysis on the flux distribution of electric machinery by FEM. Therefore, if air-gap domain was subdivided into triangular elements, computation results contain errors due to variation of element shape in air-gap because the nodal points corresponding to the rotor are displaced in analyzing domain for the time difference. In order to reduce this errors, the paper presents a application of a Macro Air-gap Element that interpolation function is obtained analytically and a means to join it with linear triangular elements in the rotating machine or in the linear machine. At the end of paper, setting up analytic domain model, it compares analytic solution with the computation results of Macro Air-gap Element appliction and that of linear triangular element subdivision only to each cases of nodal displacement. And it carries out that errors due to variation of element shape are reduced effectively by application of a Macro air-gap element.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 A
• /
• pp.425-427
• /
• 2002

In a deregulated power market, a load model considered the characteristics of electric consumers is required and the congestion management of transmission lines should be resolved in a point of economic benefits. It is essential that the optimal power flow algorithm is applied to manage transmission line congestion. Therefore, in this paper, we implement the optimal power flow with object function of social welfare maximization based linear programming and analysis the nodal prices for generations and loads through a numerical study.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.213-219
• /
• 2001

This paper deals with the free vibration of two identical circular plates coupled with a bounded fluid. An analytical method based on the [mite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. In the theory, it is assumed that the ideal fluid is filled in a rigid cylindrical container and the two plates are clamped along the plate edges. The proposed method is verified by the finite element analysis using commercial software with a good accuracy. Two transverse vibration modes, namely in-phase and out-of-phase, are observed alternately in the fluid-coupled system when the number of nodal circles increases for the fixed nodal diameter. The effect of gap between the plates on the fluid-coupled natural frequency is also investigated.

• 한국소음진동공학회논문집
• /
• 제11권9호
• /
• pp.439-453
• /
• 2001

This study deals with the free vibration of two identical circular plates coupled with a bounded fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. In the theory, it is assumed that the ideal fluid in a rigid cylindrical container and the two plates are clamped along the plate edges. The proposed method is verified by the finite element analysis using commercial program with a good accuracy. Two transverse vibration modes, namely in-phase and out-of-phase, are observed alternately in the fluid-coupled system when the number of nodal circles increases for the fixed nodal diameter. The effect of gap between the plates on the fluid-coupled natural frequencies sis also investigated.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
• /
• pp.607-614
• /
• 2002

For the accurate analysis of crack problems, considerable nodal refinement near the crack tip to capture singular stress field with sufficient accuracy to provide a useful computation of stress intensity factor is required. So, in this paper, adaptive nodal refinement scheme is proposed where nodes in restricted cell regions centered at crack tip are arranged in array for enhanced spatial resolution and adaptivity. With only cell-wise adaptive refinement scheme around crack tip fields, singularity of crack tip is sufficiently described to expect a successive crack propagate direction. Through numerical tests, accuracy of the proposed adaptive scheme is investigated and compared with the finite element and experimental results. By this implementation, it is shown that high accuracy is achieved by using iterative cell-wise solution method fur analyzing crack propagation problems.