• 대한설비공학회지:설비저널
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• 제11권3호
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• pp.9-17
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• 1982

In this paper, temperature distributions in radial fin of hyperbolic profile for steady -state with no heat generation are obtained by one-dimensional analytical method, finite difference method and experiment respectively. Heat flow rate and fin efficiency from the fin model are obtained by analytical method. To compare the exact solutions obtained by theoretical analysis with the results obtained by finite difference method, cylindrical shape is selected. Particularly, equations of finite difference method for cylindrical shape with irregular boundary are rearranged and formulated. Consequently, temperature distributions in radial fin can certify that are similar to exact solutions. From theoretical analysis, the effects according to heat flow rate and fin efficiency are related to variation of parameters which are fin thickness ${\delta}_o$, fin base temperature $T_o$, thermal conductivity K with same basic dimensions and the fleets are studied and compared.

• ETRI Journal
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• 제45권4호
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• pp.704-712
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• 2023

This paper presents a flexible finite-difference technique for analyzing the nonuniform guiding structures. Because the voltage and current variations along the nonuniform structure differ for each segment, this work considers the adaptable discretization steps. This technique increases the accuracy of the final response. Moreover, by applying the singular value decomposition and discarding the nonprincipal singular values, an optimal lower rank approximation of the discretization matrix is obtained. The computational cost of the introduced method is significantly reduced using the optimal discretization matrix. Also, the proposed method can be extended to the nonuniform waveguides. The technique is verified by analyzing several practical transmission lines and waveguides with nonuniform profiles.

• Journal of applied mathematics & informatics
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• 제42권3호
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• pp.695-708
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• 2024

In this paper we present a non-standard finite difference method for solving a fractional decay model. The proposed NSFDM is constructed by incorporating a non-standard denominator function, resulting in an explicit numerical scheme as easy as the conventional Euler method, but it provides very accurate solutions and has unconditional stability. Two examples from the literature are presented to demonstrate the performance of the proposed numerical scheme, which is compared to three methods from the literature. It is found that the method's estimated errors are extremely minimal, such as within the machine precision.

• 한국해안해양공학회지
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• 제15권3호
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• pp.190-195
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• 2003

연안 및 해안에서 발생하는 파랑변형, 조석 전파, 부유사 이동 및 확산 현상 등을 예측하기 위해서는 수치모형이 주로 사용된다 대표적인 수치모형 기법으로는 유한차분법 및 유한요소법이 있다. 유한차분법을 사용하는 경우에는 관심영역의 각 격자점에서 유한차분 방정식을 풀어야하므로, 격자망 및 경계조건 등이 설정되어야 한다. 유한차분용 격자망은 유한요소법과는 달리 격자망이 간단하지만, 지형이 복잡한 경우에 편리하게 사용 할 수 있는 격자정보 생성기법이 별로 개발되어 있지 않다. 또한, 상업용으로 많이 개발되어 있는 프로그램도 대부분 유한요소법에 근거한 수치모형에서 사용하는 격자생성을 목적으로 하고 있다. 본 연구에서는 디지타이저(Summagrid IV 기종)를 사용하여 유한차분모형을 위한 동일한 간격의 직사각형 격자 수심자료를 만드는 세부과정을 자료로 소개하고자 한다. 필요한 프로그램은 Golden Software사의 Didger(dititiger 지원 S/W)와 Surfer(gridding & contouring S/W)로서, 비교적 간단하게 정확한 수심 자료를 얻을 수 있으며, 임의의 지점 떠는 영역에 제시된 정보로부터 필요한 직사각형 격자정보를 추출하는 방법에 적용이 가능하다.

• 자원환경지질
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• 제29권2호
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• pp.183-192
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• 1996

Much computing time and large computer memory are needed to solve the wave equation in a large complex subsurface layer using finite difference method. The time and memory can be reduced by decreasing the number of grid per minimun wave length. However, decrease of grid may cause numerical dispersion and poor accuracy. In this study, we present 49 points weighted average method which save the computing time and memory and improve the accuracy. This method applies a new weighted average to the coordinate determined by transforming the coordinate of conventional 5 points finite difference stars to $0^{\circ}$ and $45^{\circ}$, 25 points finite differenc stars to $0^{\circ}$, $26.56^{\circ}$, $45^{\circ}$, $63.44^{\circ}$ and 49 finite difference stars to $0^{\circ}$, $18.43^{\circ}$, $33.69^{\circ}$, $45^{\circ}$, $56.30^{\circ}$, $71.56^{\circ}$. By this method, the grid points per minimum wave length can be reduced to 2.5, the computing time to $(2.5/13)^3$, and the required core memory to $(2.5/13)^4$ computing with the conventional method.

• 산업기술연구
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• 제21권B호
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• pp.175-185
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• 2001

A numerical model is represented to calculate the reflected waves, the runup of waves and the wave induced velocities on impermeable slopes for the normally incident wave trains of nonlinear monochromatic wave and solitary wave. The finite amplitude shallow water equations with the effects of bottom friction are solved numerically in time domain using an explicit dissipative Lax-Wendroff finite difference method. The numerical model is verified by comparisons with the other numerical results, the measured data and asymptotic results. It is found that the uprushing and downrushing of incident waves may be accurately predicted by the present numerical model. Therefore, the present numerical model can be applicable to swells as well as long waves.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2245-2252
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• 2002

Design sensitivity analysis scheme is proposed in an elasto -plastic finite element method with explicit time integration using a direct differentiation method. The direct differentiation is concerned with large deformation, the elasto-plastic constitutive relation, shell elements with reduced integration and the contact scheme. The design sensitivities with respect to the process parameter are calculated with the direct analytical differentiation of the governing equation. The sensitivity results obtained from the present theory are compared with that obtained by the finite difference method in a class of sheet metal forming problems such as hemi-spherical stretching and cylindrical cup deep-drawing. The result shows good agreement with the finite difference method and demonstrates that the preposed sensitivity calculation scheme is a pplicable in the complicated sheet metal forming analysis and design.

• 산업기술연구
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• 제11권
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• pp.85-98
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• 1991

A numerical study was performed to investigate characteristics of one-dimensional consolidation of soft clay. Results of consolidation tests with the remolded normally consolidation clay of having a very high initial void ratio were analyzed by using the numerical technique of finite difference method based on the finite strain consolidation theory, to evaluate consolidational characteristics of soft clay under surcharges on the top of clay. On the other hand, a numerical parametric study on soft clay consolidated due to its self-weight was also carried out to find its effect on one-dimensional consolidation. Terzaghi's conventional consolidation theory, finite strain consolidation theories with linear and non-linear interpolation of effective stress - void ratio - permeability relation were used to analyze the test results and their results were compared to each other to figure out the difference between them. Therefore, the validity of theories was assessed.

• Steel and Composite Structures
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• 제27권3호
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• pp.255-271
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• 2018

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.57-62
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• 2008

탄성파 수치 모형 계산에 있어서 널리 사용되는 엇갈린 격자 방법이 아니라 회전된 엇갈린 격자 방법을 사용하여 탄성파 수치 모사를 수행하였다. 표준 엇갈린 격자 방법에서는 자유 경계조건을 적용하여야 하는 단점이 있지만 회전된 격자 방법에서는 자유 경계조건을 적용할 필요 없이 물성을 부여함으로써 해결될 수 있다. 파동전파에 있어서 유한 경계 조건에서 발생하는 인공 반사파를 제거하기 위하여 최근에 뛰어난 성능을 보이는 PML(Perfectly Matched Layer)법이 많이 적용되고 있다. 이 연구에서는 PML보다 성능이 뛰어나기도 하지만 차분에 있어 파동식을 분리할 필요가 없는 CPML(Convolutional Perfectly Matched Layer)법을 회전된 엇갈린 격자법(RSG : Rotatged Staggered Grid)에 적용하고자 하였다. Cerjan법의 감쇠법과 비교한 결과 매우 효과적으로 인공 반사파를 제거할 수 있음을 알 수 있었다.