• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.256-256
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• 2021

Saint-Venant 방정식은 수평규모가 수심규모보다 큰 천수흐름을 기술하는 수리동역학 모형으로 지난 수십년간 공학적 분야에서 널리 이용되어 왔다. 최근에도 기후변화에 따른 도시 홍수의 위기 증대로 홍수위기관리의 관심이 높아짐에 따라 홍수파(flood wave), 도시침수(urban inundation), 돌발홍수(flash flood) 등의 신속한 예측을 위한 Saint-Venant 방정식의 연구가 활발히 진행되고 있다. 그러나 도시와 같은 인공구조물이 즐비한 상황에서 천수흐름을 해석하는 고전적인 수치해법들은 다양한 불연속 지형들의 존재로 인하여 불안정하며 지배방정식의 정해로 수치해가 잘 수렴하지 않는 문제가 있다. 지난 수년간 이를 해결하기 위해 불연속한 지형을 안정적으로 해결할 수 있는 수치기법의 연구가 진행되어 왔으나, 정해로의 수렴성, 정확성에 관하여 연구가 부족한 실정이다. 본 연구는 수치해법의 주요 구조를 구성하는 Saint-Venant 방정식의 불연속한 지형조건에 대한 리만 문제의 정해를 연구하였다. 쌍곡선형 시스템의 특징을 고려하여 요소파들(elementary waves)의 공식을 유도하였는데, 질량과 에너지의 보존법칙에 위배되지 않으며 운동량이송부의 비선형성과 지형의 불연속에 의한 비엄격성을 고려할 수 있는 조건을 제시하였다. 또한, 유도된 요소파들을 바탕으로 L-M & R-M 커브이론(Han et al. 2014)을 사용할 수 있는 조건과 당위성을 증명하였고, 이를 바탕으로 Saint-Venant 방정식의 정해법을 구성하였다. 리만문제의 다양한 초기조건들을 바탕으로 모든 경우의 정해 구조를 조사하였고, 이를 통해 불연속 지형에 대한 Saint-Venant 지배방정식의 정해가 다수해를 갖을 수 있음을 보였으며, 이를 근사할 수 있는 수치기법의 전략을 소개하였다.

• Water for future
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• v.24 no.1
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• pp.73-81
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• 1991

The Saint-Venant equations of the continuity and momentum principles of one-dimensional, unsteady, open-channel flow are expressed in terms of the phase velocities of constant depth, velocity, and discharge, which results in unique relationships between these phase velocities and channel velocity. A case study shows that these unique relationships developed in this study can be used as an indicator of precision of numerical solutions of the Saint-Venant equations. Further physical interpretation of these relationships and utilization to the numerical analyses of the Saint-Venant equations are to be investigated.

• KCID journal
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• v.1 no.2
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• pp.11-21
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• 1994

A numerical model for conservation form of Saint Venant equations for nonprismatic channels (CFSVE model) is developed. The model is based on a finite difference solution of the Preissmann scheme. The CFSVE model consists of data pre-management program (D

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.4 s.19
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• pp.1-8
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• 2005

In this study, a numerical model combined by a river model and an inland model developed to simulated a flood event. The river model describing an inundation in a river solves the two-dimensional Saint Venant equations with a finite difference method. The inland model based on the ILLUDAS describes the conveyance capacity of a storm sewer system. The combined model is applied to a real situation. The model simulates reasonably the real flood event occurred in a river and inland simultaneously.

• 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 the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.159-164
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• 2008

This study simulated the flood inundations of the Nakdong River catchment running through Yangsan, a small city located in the south eastern area of Korea by using the depth averaged two-dimensional hydrodynamic numerical model. The numerical model employs the staggered grid system including moving boundary and a finite different method to solve the Saint-Venant equations. A second order upwind scheme is used to discretize the nonlinear convection terms of the momentum equations, whereas linear terms are discretized by a second order Leap-frog scheme(Cho and Yoon, 1998). The numerical model was applied to a real topography to simulate the flood inundation of the Yangsan basin in Yangsan. The numerical result for urban district was visualization for three dimension. These results can be essentially utilized to construct the three dimensional inundation map after building the GIS-based database in local public organizations in order to protect the life and property safely.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.129-136
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• 2008

All measures to cope with flooding rely on flood predictions to some extent. To investigate these predictions such as maximum water level or inundation area, a numerical model has been developed. The governing equations of the model are the two-dimensional Saint-Venant equations. The governing equations are discretized explicitly by using the leap-frog scheme and upwind scheme based on quadtree grids. The predicted numerical results have been verified by comparing to those of a Thacker problem. As a result of verifications, the present model is not only nearly four times as efficient as uniform grids but also in close agreement with the previous models. Next, the developed model is applied to several flood events in the Uiryeong basin. A general tendency is found that as a frequency is increasing, overall water levels including peak water level are increasing. At only a 500 year frequency, maximum water level is higher than 18.5 m. Therefore, it can be predictable that inundation will be generated in a 500 year frequency.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.231-236
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• 2006

본 연구에서는 단일 첨두를 갖는 가상의 균일하도구간과 홍수피해가 극심하게 나타나고 있는 낙동강유역에 대하여 Saint-Venant 방정식을 음해적으로 유한차분하여 수치적으로 해석한 수리학적 하도추적을 FLDWAV 모형을 이용하여 수행함으로써 홍수파의 전달양상과 천변저류지의 홍수 저감영향을 분석하였다. 균일하도구간에 대한 적용은 천변저류지의 규모와 운영조건 그리고 설치위치에 따른 홍수 저감영향을 비교검토함으로써 천변저류지의 최적 규모 및 설치위치를 결정하는데 효과적인 참고 자료가 될 것으로 기대된다. 또한 낙동강유역에 대한 적용에서는 낙동강 하천정비 기본계획에 근거한 계획홍수량으로 모의를 수행하였다. 낙동강 유역종합 치수계획 보고서에 제시된 10개의 천변저류지에 대한 모의를 통해 실제 낙동강유역의 홍수 저감영향을 분석함으로써 하천제방 계획시 경제적인 하천 제방단면 결정을 위한 참고 자료 및 효과적인 홍수피해 경감대책 수립을 위한 기초 자료를 제시하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.381-387
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• 2016

In this paper, the methodology applied to the improvement of stress analyses is extended to free vibration and buckling analyses. The essence of the methodology is the Saint-Venant's principle that is applicable to beam and plate models. The principle allows one to dimensionally reduce three-dimensional elasticity problems. Thus the methodology can be employed to vibration and buckling as well as stress analysis. First, the principle is briefly revisited, and then the formations of classical beam theories are presented. To improve the predictions, the perturbed terms (unknowns) are introduced together with the warping functions that are calculated by stress equilibrium equations. The unknowns are then calculated by applying the equivalence of stress resultants (i.e., Saint-Venant's principle). As numerical examples, cantilever and simply supported beams are analytically solved. The results obtained are compared with those of the classical beam theories. It is shown that the methodology can be used to improve the predictions without introducing shear correction factors.

• Water for future
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• v.15 no.1
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• pp.57-62
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• 1982

In order to make a numerical modeling for the one dimensional unsteady flow which expressed by Saint Venant partial differential equations, Preissman's implicit schem was used, and it's stability and accuracy was investigated. By introducing recurrence relations make it possible to use double sweep algorithm. Effective parameters to the result were the values of the C$$ and the Chezy coefticient. In order to get numerical solutions whith enough accuracy, C$$ should not be far from the value of1, and when the criteria of the $\theta$ was 0.6<$\theta$<1.0, the rewult was always stable for any condition. This model should be calibrated by real field data, and expected to be developed for the simulation of the river system and to the long wave analysis for one dimensional coastal zone problem.