• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.664-668
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• 2008

본 연구에서는 비정상상태 자유수면 모의를 위해 2차원 유한체적법을 이용한 수치모형을 개발하였으며, 이론적인 해석해 및 수리실험을 통한 실측자료를 이용하여 검증하였다. 개발된 모형은 지배방정식으로 비선형 및 보존형 2차원 천수방정식(shallow water equation)을 이용하였으며, 동적메모리 할당 기능이 포함된 Fortran-90으로 코딩되었다. 또한 구조화된 격자 및 비구조화 격자 시스템에도 적용될 수 있도록 모형을 구성하였으며, 불규칙한 하상지형에 의해 수치진동을 감소시키기 위해 본 모형에 well-balanced HLLC 기법을 적용하였다. 모형의 적용성을 검증하기 위하여 1차원의 경우 젖은/마른 하상 조건하에서의 댐 붕괴파 문제와 하상이 변화하는 지형 구간을 통과할 때 발생되는 천이류에 대한 문제 그리고 시간에 따라 변화하는 수위와 지형 조건에서의 wetting & drying에 대한 문제에 적용하였으며, 2차원의 경우 전통적인 댐 붕괴파 문제 및 구조물에 미치는 댐 붕괴파의 영향에 대한 수리모형실험을 통한 실측자료를 이용하여 검증하였다. 검증결과 본 모형을 통해 계산된 수치해는 이론적인 해석해와 실측자료에 거의 정확히 일치하였으며, 향후 실제 하천 자료를 이용하여 모형의 현장 적용성을 검증할 것이다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.3
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• pp.101-107
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• 1990

In this work, one-dimensional simulation is carried out for PT-GaAs Schottky barrier diodes with finite difference method. Shockley's semiconductor governing equations: Poisson equation and current continuity equation are discertized, and linearized by Newton-Raphson method. The linear system of equation is solved by Gaussian elimination method until convergence is achieved. The boundary condition for this equation is taken from thermionic emission-diffusion theory. Simulation is done for PT-GaAs epitaxial-layer Schottky barrier diodes. The claculated results of electron and potential distribution are shown. Simulation results show exellent agreement with experiments.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.949-958
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• 2004

A combined experimental and numerical effort is presented for investigation of reflection of irregular waves due to rectangular submerged breakwaters. In the numerical model, the Reynolds equations are solved by a finite difference method and k-$\varepsilon$ model is employed for the turbulence analysis. To track the free surface displacement, the volume of fluid method is employed. Numerical predictions of transmission and reflection coefficients are verified by comparing to laboratory measurements. Very reasonable agreements are observed. The reflection coefficients become stronger in proportion to numbers of submerged breakwaters.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.45-52
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• 2007

In this study, the flood inundations of the Nam River catchment running through the Uiryeong and Haman regions have been simulated using the numerical model based on quadtree grids. The nonlinear Saint Venant equation is employed as the governing equation for a numerical model in this study. The governing equations are discretized explicitly with a finite difference leap-frog scheme on adaptive hierarchical quadtree grids. Results from this study are compared with those of established numerical models such as the HEC-RAS and the FLUMEN. A numerical model is also simulated according to the frequency variations of flood event. Obtained numerical results show good agreements with them of commercial models. It is found from this study that the flood inundations in the studied area can be occurred at a 500 year frequency event.

• Journal of Korea Water Resources Association
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• v.38 no.5 s.154
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• pp.355-364
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• 2005

In this study, flood inundations have been simulated by using the numerical model FLUMEN solving the shallow-water equations with a finite volume method. Before applying to a real problem, the numerical model is first applied to simplified problems. Obtained numerical results are verified by comparing with available analytical solutions and laboratory measurements. Reasonable agreements are observed. The model is then applied to a simulation of flood events with real geometries. The results of this study will provide basic information to make a flood inundation map.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.166-177
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• 2006

The accuracy impact of using high-order Boussinesq-type model as compared to the typical order model is examined in this paper. The multi-layer model developed by Lynett and Liu(2004a) is used for simulating of wave breaking over a shelf region. The nonlinearity of the waves tested, ${k_0}{A_0}$, ranges from 0.029 to 0.180. The overall agreement between the two-layer model and the hydraulic experiments are quite good. The one-layer model overshoals the wave near the breakpoint, while the two-layer model shoals at a rate more consistent with the experimental data.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.534-541
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• 2015

This study was presented how to interpret a laminated cylindrical shell having both ends supported condition are simple, and by identifying the three-dimensional stress characteristics. The governing equations were using the concept of finite element assuming the conversion into ordinary differential equations and partial differential equations by numerical analysis using the finite strip method. In particular, a function performed for the three-dimensional laminated cylindrical shell having a simple support condition were analyzed for the case composed of a specific function of the beam consisting of a trigonometric function. Layer material and layer thickness of a steel or concrete, the cylindrical length and the like by varying the parameters variously examine the effects of multi-layer cylindrical shell.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.77-94
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• 1991

A finite difference method based on MAC method is used to simulate free-surface waves around a ship. Euler equations and continuity equation are differentiated using the forward time and central space, and solved by time marching scheme. By the employment of variable mesh system in horizontal and vertical direction, the numerical accuracy of wave simulation results is grossly improved. To verify the improvement of numerical accuracy, some numerical simulations are accomplished for Wigley, Series 60($C_{b}$=0.6) and a bulk carrier model. The computational results are compared to the various experimental data and show good agreements.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.705-713
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• 2003

To investigate the run-up heights of nearshore tsunamis in the vicinity of a circular island, a numerical model has been developed based on quadtree grids. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using a finite difference leap-frog scheme on adaptive hierarchical quadtree grids. The quadtree grids are generated around a circular island where refined with rectangular or circular domain. Obtained numerical results have been verified by comparing to available laboratory measurements. A good agreement has been achieved.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.30-40
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• 2004

In the present study, a numerical method has been developed for the calculation of the gust response of an airship using unstructured meshes. A preconditioning method is incorporated for accurate and efficient computations of the Euler equations at the low Mach number range. A simple sharp-edged gust is used as a gust model. The accuracy of the present method is demonstrated through comparisons with an exact line theory. The numerical results show that the variation of lift is relatively larger than that of moment. It is also shown that the static stability of the airship is enhanced with the use of control fins.