• 대한조선학회논문집
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• 제39권4호
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• pp.1-10
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• 2002

초기쇄파의 수치모사에는 지금까지 경계적분법이 주로 쓰여왔고, 이 방법은 과도한 계산시간의 문제를 제외하고는 어느 정도 성공적이라고 할 수 있다. 본 논문에서는 쇄파실험을 수치모사하기 위한 새로운 수치기법을 보였다. 이 수치기법은 고차 스펙트럴/경계요소법과 경계적분법을 순차적으로 사용하며, 계산시간을 현저히 줄여준다. 조파 및 파 에너지 집중과정은 고차 스펙트럴/경계요소법에 의해 효율적으로 수치모사되고, 파의 전복과정만이 경계적분법에 의해 계산된다. 계산예에서 높은 입자속도와 가속도 등 쇄파의 두드러진 특성이 보여졌다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.619-624
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• 2007

Spectral element method (SEM) is introduced for the fully coupled structural dynamic problems, In this paper, the beam with passive constrained layered damping (PCLD) treatments is considered as a representative problems. The beam consists of a viscoelastic layer that is sandwiched between the base beam structure and an elastic layer, The fully coupled equations of motion for a PCLD beam are derived, The equations of motion are derived first by using Hamilton's principle, From this equations of motion, the spectral element is formulated for the vibration analysis by use of the SEM, As an illustrative example, a cantilevered beam is considered. It is shown that, as the thickness of VEM layer vanishes, the results become a simple layer beam's that.

• 한국해양공학회지
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• 제20권6호
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• pp.67-74
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• 2006

A high-order spectral/boundary-element method is newly adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time-domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. By the combination of these two methods, the wave-making problems by a submerged sphere oscillating with large amplitude under the free~surface are solved in time-domain. Through the example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown and discussed.

• 동력기계공학회지
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• 제14권6호
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• pp.75-82
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• 2010

In this study, the topics for free-surface wave simulation, nonlinear hydrodynamic force, and the critical resonance frequency of so-called ${\tau}=U{\omega}/g$=1/4 are discussed. A high-order spectral/boundary element method is newly adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. By the combination of these two methods, the wave-making problems by a submerged sphere oscillating with forward speed under the free-surface are solved in time domain.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.749-754
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• 2007

In this paper, the vibration of a rotating shaft with a thin rigid disk is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. The spectral element method is used for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 춘계학술대회논문집; 부산수산대학교, 10 May 1996
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• pp.328-334
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• 1996

Finite Element Method(FEM) is the most popularly used method in analyzing the dynamic behaviors of structures. But unless the number of finite elements is large enough, the results from FEM are somewhat different from exact analytical solutions, especially at high frequency range. On the other hand, as the Spectral Element Method(SEM) deals directly with the governing equations of structures, the results from this method cannot but be exact regardless of any frequency range. However, despite two dimensional structures are more general, the SEM has been applied only to the analysis of one dimensional structures so far. In this paper, therefore, new methodologies are introduced to analyze the two dimensional plate using SEM. The results from this new method are compared with the exact analytical solutions by letting the two dimensional plate be one dimensional one and showed the dynamic responses of two dimensional plate by including various waves propagated into x-direction.

• 한국대기환경학회지
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• 제7권3호
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• pp.189-196
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• 1991

In recent years spectral methods have been found to be a powerful tool for the numerical solution of hynamic differential equations. The main attraction of spectral method is accuracy even though it is generally difficult to implement and solve the complex problems using spectral method. We introduced diffusion equations describing the state of air pollution and solved by pseutospectral method in dimensionless form. The results were compared with both those of other numerical methods and analytical solutions. Comparing with finite difference method and finite element method, spectral method shows the highest accuracy for one dimension problem in this study. Also, the results of two dimensional diffusion problems show good agreement with analytical solutions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.923-926
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• 2007

In this paper, the vibration of a rotating shaft with a thin rigid disk is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. A spectral element model is developed by using the variation method for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element. The result of vibration analysis by finite element method is compared to the result of this research.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.181-186
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• 2006

본 논문에서는 Freak Wave의 생성원인에 대하여 간략히 논의하였으며, 이 중 파랑-조류 비선형 상호작용에 대한 이론 및 수치적 해석기법의 역사와 장단점 등을 기술한다. 본 연구에서는 파랑-조류 상호작용에 대한 수치모델링 및 해석 기법을 개발하고 있다. 개발 중인 수치해석 기법은 공간적으로 불균일한 조류와 파랑의 비선형 상호작용을 해석하기 위하여 Navier-Stokes 방정식을 이용하여 유동현상을 모델링하였으며, 이산화를 위하여 스펙트랄요소법(Spectral Element Method; SEM)을 이용하였다. 또한 자유표면의 운동을 효과적으로 기술하기 위하여 ALE(Arbitrary Lagrangian-Eulerian)기법을 사용하였다. 본 연구의 유동 모델과 수치해석기법의 과정과 특성, 그리고 장점 등에 대하여 논의하였으며, 초기적인 수치해석 결과를 제시하였다. 이를 바탕으로 개발된 수치해석기법의 정확성 및 수렴성을 확인할 수 있다.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.199-209
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• 2001

Modal analysis method (MAM) is introduced for the fully coupled structural dynamic problems. In this paper, the beam with active constrained layered damping (ACLD) treatment is considered as a representative problem. The ACLD beam consists of a viscoelastic layer that is sandwiched between the base beam structure and an active piezoelectric layer. The exact damped natural modes are spectrally formulated from a set of fully coupled dynamic equations of motion. The orthogonality property of the exact damped natural modes is then derived in a closed form to complete the modal analysis method. The accuracy of the present MAM is evaluated through some illustrative examples: the dynamic characteristics obtained by the present MAM are compared with the results by spectral element method (SEM) and finite element method (FEM). It is numerically proved that MAM solutions become identical to the accurate SEM solutions as the number of exact natural used in MAM is increased.