• 한국수산과학회지
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• 제18권1호
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• pp.15-22
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• 1985

The study on computation time, accuracy, and convergency characteristic of the implicit finite difference method is presented with the variation of the space increment and time step in a two-dimensional transient heat conduction problem with a dirichlet boundary condition. Numerical analysis were conducted by the model having the conditions of the solution domain from 0 to 3m, thermal diffusivity of 1.26 $m^2/h$, initial condition of 272 K, and boundary condition of 255.4 K. The results obtained are summarized as follows : 1) The degree of influence with respect to the accuracy of the time step and space increment in the alternating-direction implicit method and Crank-Nicholson implicit method were relatively small, but in case of the fully implicit method showed opposite tendency. 2) To prescribe near the zero for the space increment and tine step in a two dimensional transient problem were good in a accuracy aspect but unreasonable in a computational time aspect. 3) The reasonable condition of the space increment and the time step considering accuracy and computation time could be generalized with the Fourier modulus increment, F, ana dimensionless space increment, X, irrespective of the solution domain.

• 대한수학회논문집
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• 제11권2호
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• pp.495-501
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• 1996

There is currently a regain of interest in ADI (Alternating Direction Implicit) method as a preconditioner for iterative Method for solving large sparse linear systems, because of its suitability for parallel computation. However the classical ADI is not applicable to FE(Finite Element) matrices. In this paper wer propose a Block-ADI method, which is applicable to Finite Element metrices. The new approach is a combination of classical ADI method and domain decompositi on. Also, we provide a partial proof of the convergence based on the results from the regular splittings, in case the discretization metrix is symmetric positive definite.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.131-134
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• 2004

This paper has been studied a ADI-FDTD(Alternating Direction Implicit Finite Difference Time Domain ) algorithm using an alternating Direction time-stepping scheme for GPR( Ground-Penetrating Radar ) system simulation. We did the numerical formulations for three-dimensional ADI-FDTD algorithm and PML(Perfect Matched Layer), and made an simple experiment on a arbitrary cube with programed algorithms. And then we compared its computed results with those of conventional FDTD.

• 한국항만학회지
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• 제13권1호
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• pp.123-132
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• 1999

It is very important to quantitatively assess the movement of sea water and pollutant dispersion before or after constructing shore structures such as breakwater considering marine environment and long-term utilization of those structures. This assesment is possible through the use of simulation models designed to predict water movement and pollutant dispersion in a certain area. In this study the numerical computations were carried out to predict the sea water quality in the Ilgwang Harbor located at the east coast of Pusan. The flow patters were investigated before and after the development of Ilgwang Harbor. The computational models adopting ADI Method (Alternating Direction Implicit Method) were used here and were already verified from the previous studies. As a results of this study the tidal exchange in Ilgwang Harbor after development proved to be worse due to the increased semi-enclosed at the harbor limit. In order to improve the water quality of this area after development a new method was proposed to improve water quality in the semi-enclosed bay by creation and control of tidal residual currents. For this purpose the unsymmetric structures so called bottom roughness were introduced in this study. The simulation was carried out on the basis of the study by Komatsu et. al. and Gug and we made a conclusion that it is possible to generate a new tidal residual current and to increase the tidal exchange by application of bottom roughness arrangement.

• 한국항만학회지
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• 제12권2호
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• pp.303-312
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• 1998

It is necessary to quantitatively asses the influence of tidal currents to analysis the coastal current patterns before or after constructing offshore structures like as breakwaters. This assesment can be made through the use of simulation models designed to reproduce the water movements of the area. And it is very important to predict a phenomenon of pollutant dispersion in the area. In this study, in order to predict the changes of sea water quality for the port development plan, Ilgwang harbour, located at the east coast of Pusan, the numerical computations were carried out. The flow patterns were investigated before and after the development of the harbour bay and coastal area connected on it. The computational models are an extension of earlier work on the flow which used the ADI Method (Alternating Direction Implicit Method) in appling to Osaka Bay by KANEKO et al. The transport of pollutant constituents depends upon the currental characteristics of the water-transporting medium. In the currental flow model, water velocities and water levels are computed throughout the regions of it. These value are then used in the mass-balance equation to obtain the pollutant-constituent transport. As a result of this research, the present water quality of Ilgwang harbour and the coastal areas connected on it was proved out some good condition. The changes of sea water quality due to the port development plan of the Ilgwang habour bay and the coastal area were not large compared with the present condition, but it will be likely able to get worse by increasing the semi-enclosed areas in the harbour bay. In order to improve the water quality of the area after development, the method to activate tidal exchange in the area can be needed, as a mitigation technique.

• Tribology and Lubricants
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• 제13권4호
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• pp.53-59
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• 1997

The camshaft locus at camshaft beating in a direct acting OHC valve train system has been investigated using the transient method. Forces applied to the camsfiaft are composed of two components, one is the transfer force between the cam and the tappet, the other is the frictional force. These forces have been calculated using the lumped mass model and the elastohydrodynamic lubrication theory. The alternating direction implicit method has been used for the numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for the transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As a result of the analysis, it has been found that camshaft bearings were mainly in the hydrodynamic lubrication condition.

• 대한전자공학회논문지TC
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• 제40권5호
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• pp.181-186
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• 2003

본 논문에서는 관심주파수의 파장에 비하여 매우 섬세한 구조의 해석에 있어서 기존의 FDTD보다 효율적인 해석이 가능한 ADI-FDTD의 분산오차에 대하여 연구하였다. 2-D ADI-FDTD에 적합한 분산식을 제안하였으며 기존의 분산식들과 비교하였다. 수치적인 해석을 통하여 제안된 2-D ADI-FDTD 분산식이 수치결과와 일치함을 확인하였다.

• 한국전산유체공학회지
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• 제2권1호
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• pp.13-20
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• 1997

A fundamental study for the numerical scheme to simulate unsteady nonlinear waves by solving Euler equations is presented. First a conservation form and a non-conservation form of the Euler equations with a free surface fitted coordinate system are compared. Next, a time splitting fractional step method and an alternating direction implicit(ADI) method for the time integration are compared. For the comparative study, flow calculations around a bottom bump in a channel and a NACA 0012 hydrofoil in a flume are performed. The results show that the ADI method with a third order upwind differencing scheme is very efficient in reducing the computing time with keeping the accuracy, And, there is no distinct difference between two expression forms except that the non-conservative form shows faster wave propagating velocity than the conservation form. Some results are compared with experiments and show good agreement.

• 태양에너지
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• 제2권1호
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• pp.1-8
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• 1982

A theoretical study by numerical method has been performed on the natural convection of an air contained in enclosures. The enclosures have rectangular cross section with one vertical wall heated and the other cooled, and with two horizontal partition plates of finite thermal conductivity. Steady two-dimensional flow was assumed. The computation was executed by means of the Implicit Alternating Direction (I.A.D) finite-difference method. Two partition plates of Aluminium whose thickness were 0.05mm was employed in computation. Isothemals, streamlines, local Nusselt numbers and mean Nusselt numbers were obtained for various Grashof numbers and aspect ratio and these results were compared with those in the case of the enclosure with two horizontal insulated plates. From the present results, the heat transfer in the case of partition plates was greater than that in the case of insulation. This study suggests a method to measure the overall heat-transfer of coefficient in double walls which supported by partition plates for insulative construction.

• 한국전자파학회논문지
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• 제17권9호
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• pp.890-894
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• 2006

본 논문은 무조건 안정의 특징을 갖는 ADI-FDTD의 특성을 효과적으로 적용하기 위한 가변 분해능 시간 영역 전자파 해석법을 제안한다. 제안된 해석법은 관심 주파수 영역에서 정확도를 유지하면서 분해 시간 간격을 증가시켜 계산 시간을 감소시킬 수 있다.