• Water for future
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• v.29 no.6
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• pp.155-166
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• 1996

A finite element model for simulating gradually and rapidly varied unsteady flow in open channel is developed based on dynamic wave equation using Petrov-Galerkin method. A matrix stability analysis shows the selective damping of short wave lengths and excellent phase accuracies achived by Petrov-Galerkin method. Whereas the Preissmann scheme displays less selective damping and poor phase accuracies, and Bubnov-Galerkin method shows nondissipative characteristics whicn causes a divergence problem in short wave length. The analysis also shows that the Petrov-Galerkin method displays the desirable combination of selective damping of high frequency progressive waves over a wide range of Courant number and good phase accuracy at low Courant number. Therefore, the Petrov-Galerkin can be effectively applied to gradually and rapidly varied unsteady flow.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.299-303
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• 2002

수정된 SIMPLE법과 VOF의 결합으로 predictor-two step corrector-VOF라고 불리는 새로운 알고리즘이 주조 시 용탕 충전과정을 해석하기 위해 개발되었다. 운동량보존으로부터 유도된 새 2단계 속도 경계조건 처리법은 용탕의 자유표면을 추적하는 데 사용되었다. 본 연구에서는 2개의 예제 계산을 통해 계산정확도와 속도에 대한 Courant 수의 영향을 살펴보았다. 그 결과 적당한 Courant 수의 증가는 계산 정확도의 감소 없이 용탕 계산 속도를 향상시킬 수 있는 것으로 나타났다. 또한 만족할 만한 계산 정확도와 효율이 이 알고리즘의 실제 제품 해석을 통해 얻어졌다.

• The Journal of Korean Philosophical History
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• no.50
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• pp.269-303
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• 2016

There are two ways of viewing the Taoism of the Joseon dynasty. One is to view it from the point of view in Joseon, another is to view it from the outside of Joseon, i.e. foreigners' point of view. Maurice Courant(maurice courant,1865~1935)'s Bibliographie Coreenne is the Korean first bibliography(書誌) recorded from the latter's point of view. This research examined the Taoist scripture in Maurice Courant's Bibliographie Coreenne. Maurice Courant classified the Taoist scripture of the Joseon into three: '1. Sacred books(經書類)', '2. Worship of Gwanseongjegun(關聖帝君), Munchangjegun(文昌帝君), Buwoojegun (孚佑帝君)', '3. Various works'. Through this category, it was determined that the belief in three gods (Gwanseongjegun Munchangjegun Buwoojegun) was widely prevalent in the Joseon dynasty in the late 19th century. In the chapter 1, he composed the books of representative Taoist scripture as Lao-tzu and Chuang-tzu, 'God(太上)', and 'King of heaven(九天上帝)'. Maurice Courant determined in chapter 2 that 1890s' Joseon Gwanwoo (關帝) belief was activated, and mentioned 'Musangdan(無相壇)', namely, Joseon's first religious organization. However, he could not determine that the scriptures relevant to three gods were recorded to be divine revelations uttered by gods. 19th century's 'Musangdan' was not introduced by being imported with Chinese Taoist scripture, but was published with the Joseon Taoist scripture through Gangpil(降筆: recording divine revelations uttered by gods). Also, through Maurice Courant's Bibliographie Coreenne, the point that 'belief in three gods' was prevalent in the social leader group during that period could be determined. The reason how such research could be possible seems, because Maurice Courant had Korean assistants who were good at Chinese classics. In chapter 3, Maurice Courant arranged the books based on Taoist ethic and the scriptures on Taoist social practical movement. Through the interpretation of Taoism bibliographies included in Maurice Courant's Bibliographie Coreenne, first, it could be determined that belief based on the three gods(三聖信仰) was prevalent during the 19th century, second, there were lots of the Taoist scriptures made in the late Joseon, third, the first Taoist religious organization and Taoist social movement form could be investigated.

• Water for future
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• v.26 no.3
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• pp.137-148
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• 1993

A hybrid finite difference method for the longitudinal dispersion equation was developed. The method is based on combining the Holly-Preissmann scheme with the fifth-degree Hermite interpolating polynomial and the generalized Crank-Nicholson scheme. Longitudinal dispersion of an instantaneously-loaded pollutant source was simulated by the model and other characteristics-based numerical methods. Computational results were compared with the exact solution. The present method was free from wiggles regardless of the Courant number, and exactly reproduced the location of the peak concentration. Overall accuracy of the computation increased for smaller value of the weighting factor, $\theta$ of the model. Larger values of $\theta$ overestimated the peak concentration. Smaller Courant number gave better accuracy, in general, but the sensitivity was very low, especially when the value of $\theta$ was small. From comparisons with the hybrid method using the third-degree interpolating polynomial and with split-operator methods, the present method showed the best performance in reproducing the exact solution as the advection becomes more dominant.

• Journal of Korea Water Resources Association
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• v.30 no.2
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• pp.143-154
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• 1997

A numerical model for solving advection-diffusion equation is presented by splitoperator method combining the Holly-Preissmann scheme with a fifth-degree interpolating polynomial for advection operator and the explicit scheme porposed by Hobson et al. for diffusion operator. To examine the developed model, the obtained numerical solutions are compared with both the analytic solution and those from the existing models for the instantaneous source (Gaussian hill) and the continuous source (advanced front) at upstream boundary with constant velocity and diffusivity condition. For the various cases having different Courant and Peclet numbers, it is shown that the present study provides stable solutions even for Courant numbers exceeding one. The result obtained by the present study also agree well with existing analytical solutions for both cases. The proposed explicit scheme somewhat releases the conventional restriction of explicit schemes for determining the time step size and provides satisfactory results for relatively large time step size.

• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.99-110
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• 1999

The method of moments, a Lagrangian scheme, considers the zeroth, first, and second moments of the grid cell spatial distributions of the concentration and then advects the concentration by maintaining conservation of the moments. The reasonable inital description of the first and second moments as well as the mean concentration, the zeroth moments, in grid element is important in the method of moments. In this study, the description methods of each initial moment are reviewed, and the method of moments is extended to overcome the restrictions of Courant number. Its performance is compared with those of available Eulerian and Lagrangian schemes. As the results, the method is successfully extended to overcome the stability restriction and is an accurate scheme for the advection simulation of concentration distribution, especially of which the gradient is steep. In addition, the method is very promising scheme in terms of computational efficiency when the mixing is confined in a relatively small region to the entire domain in two-dimensional problem.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.481-489
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• 2016

Method of characteristic(MOC) has been widely used as a transient analysis technique for pressurized pipeline systems. There are substantial studies using MOC for the water hammer triggered through instantaneous valve closures, pump stoppage and pump startup for pipelines systems equipped with a centrifugal pump. Considering restrictions of MOC associated with courant number condition for complicated pipeline systems, an impulse response method(IRM) was developed in the frequency domain. this study implements the impact of centrifugal pump using transfer function in frequency domain approach. Using pump performance curve and the affinity law, this study formulated transfer functions which relate complex pressure head at upstream of pump system to that of downstream location. Simulations of simple reservoir-pump-valve system using IRM with formulated transfer function were similar to those obtained through MOC.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.83-89
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• 2017

Numerical simulations of ship resistance have been performed to compare spatial characteristics of Courant number when using structured and unstructured meshes. When Euler scheme was used for time integration, the structured mesh provided a more efficient calculation because the calculation time interval was larger than that of unstructured mesh. The automatic generation of very small meshes in the unstructured mesh was mainly responsible for the limitation of calculation time interval. When local time stepping Euler scheme was applied, however, the ship resistance of unstructured mesh showed a rapid convergence while a slow convergence of ship resistance in structured mesh was caused by the small time interval in bulbous bow.

• KLA journal
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• v.11 no.1
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• pp.7-11
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• 1970

불란서인 ‘모리스 · 쿠우랑’(Maurice Courant 1865-1925)은 이조 말 주한 불란서 공사관 서기로 근무하면서 당시 우리 나라 사람으로서도 생각하지 못하였던 한국의 서지에 대하여 많은 관심과 흥미를 가지고 다년간 여러 가지 어려움을 극복하면서도 경범하게 또한 세밀하게 조사 연구하여, 3,821종의 한국서적을 해제 수록한 ‘한국서지’(Bibliographie Coreenne) 전 4권을 1894-1899년에 발간하였고, 이책 이외에도 한국의 문화와 서지에 관한 저작과 논문을 많이 발표하였다. 특히 전기한 ‘한국서지’는 우리나라 고전을 대외적으로 소개한 시초의 것이라고 할 수 있다. 이에 대하여 1896년 그의 본국의 불란서에서도 그의 공적을 인정하여 문예 아카데미로부터 ‘스타니슬라 · 쥘리앙 상’(Stanisla Julien)을 받게까지 되었던 것이다. 우리는 이와 같은 그의 한국의 문화와 서지연구에 대한 공적을 때 늦은 감이 없지 않으나 우리 나라로서는 그의 유족이라도 찾아서 그의 공적을 치하하여야 마땅할 것이며, 이렇게 함으로써 한불 양국간의 우호와 세대 증진에 기여할 것으로 사료되기에 그의 업적에 관한 자료를 게재하는 것이다.

• Water for future
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• v.29 no.5
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• pp.139-150
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• 1996

This paper presents the effect of numerical parameters, such as grid size and grid ratio, on the outflow hydrograph of a unit-width plane in the linear Muskingum-Cunge method. The numerical results depend on Courant number C and cell Reynolds number D, two physically and numerically meaningful parameters. As C approache 1 and D increases, the numerical dispersion-relating oscillations are difficult to occur. The numerical oscillations occur in the front of a propagating wave for C < 1, while smaller oscillations occur behind the wave for C > 1 due to the numerical diffusion effect. For a plane with a small value of characteristic reach length L (e.g., a steep plane), the numerical solution of the Muskingum-Cunge method is similar to that of the kinematic wave method, which shows no wave attenuation. However, for a plane with a large value of L (e.g., a mild plane), the Muskingum-Cunge method leads to the diffusion waves which are essentially independent of the Courant number. Accordingly, the Muskingum-Cunge method will be suited for the routing of the catchment with relatively mild slopes.