• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.40-49
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• 1999

A Finite Volume Method for the two-dimensional incompressible, two-fluids Navies-Stokes equation and level-set scheme are used to analyse the interface of two fluids, free-surface flow. The numerical characteristics and the applicability of level-set scheme are brief1y investigated and appraised by solving oscillating small surface wave in a water tank and dam break problems. In the numerical results, a method for improving the convergence of the solution is presented.

• Journal of Korea Water Resources Association
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• v.36 no.1
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• pp.1-11
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• 2003

This paper describes a finite volume, two-dimensional model. It adopts a recently developed essentially non-oscillatory(ENO) schemes based on the Lax-Friedrichs solver, which was modified for a finite volume grid, and employs a modified MUSCL(Monotonic Upstream centered Scheme for Conservation Law) for second-order accuracy in space. To demonstrate the applications of the model, it is applied to solve the 1-D and 2-D dam-break problems. The model in conjunction with the modified MUSCL showed a better agreement with analytical solutions than the minmod function in 1-D dam-break problems and is satisfactorily validated with documented published data in 2-D dam-break problems. The model was applied to tidal wane entering channel at one end, and the results showed a good agreement with analytical solutions. In the channel with reflective boundary conditions specified at the extremities, the model was capable of accurately simulating the wave propagation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.210-211
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• 2018

In general, the dam break problem is demonstrated to simulate open-channel disturbance due to large violent waves. These days, the large violent waves at shore and coastline can be seen frequently such like tsunami. The conventional computational fluid dynamics program based on Grid system, can be used to simulate this problem with large deformation of free surface in the restricted condition due to its limitation. The particle method based on fully Lagrangian approach is able to simulate large deformation of free surface by tracking each particles. In this study, the simulation of disturbance of mobile-bed due to large violent waves was investigated by using particle method.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.112-116
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• 2017

Present study investigated the influence of time step size, turbulent eddy viscosity, and the number of layer on rapid and unsteady propagation of dam break flow. When the time step size had a value such that it resulted in Cr of 0.89, a significant numerical oscillation was observed in the vicinity of the wave front. Higher turbulent viscosity ensured smooth and mild slope of velocity and water stage compared with the flow behavior by no viscosity. The vertical velocity at the lower layer positioned near the bottom showed lower velocity compared with other layers.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.279-290
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• 1998

The height and speed of the shock wave are critical data in flood-control operations or in the design of channel walls and bridges along rivers with high flow velocities. Therefore, a numerical model is needed for simulating flow discontinuity over a wide range of conditions. In this study, a governing equation. As a Riemann solver Roe(1981)'s one is used. The model employs the modified MUSCL for handling the unstructured grids in this research. this model that adopts the explicit tradditional twl dimmensional dam break problems, two hydraulic dam break model is simulations, and a steady state simulation in a curved channel. Conclusions of this research are as follows : 1) the finite volume method can be combined with the Godonov-type method that is useful for modeling shocks. Hence, the finite volume method is suitable for modeling shocks. 2) The finite volume model combined with the modified MUSCL is successful in modeling shock. Therefore, modified MUSCL is proved to be valid.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.133-133
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• 2011

본 연구에서는 3차원 수치모형을 이용하여 댐붕괴파의 전파특성에 대한 모의를 수행하였다. 적용된 수치모형은 ANSYS CFX(v. 13) 모형으로 진보된 유동해석기법과 편리한 workbench 환경이 결합된 강력한 GUI 환경을 통해 작업하기 편리하며, 빠르고 정확한 해석결과를 제공하는 전산유체역학 도구로 국내외에서 이용되고 있다. 본 연구에서는 기존의 댐 붕괴파 특성 분석과 관련된 수리모형실험(Soares Frazao 등, 2004: Soares Frazao와 Zech, 2008) 자료를 이용하여 모의를 수행하였으며, 지점별 실측자료와 2차원 유한체적모형(정 등, 2009, 2010)에 의한 결과와의 비교를 통해 적용성 검증을 수행하였다. 또한 3차원 모형 적용 시 중요한 매개변수로 고려되는 수로바닥 및 벽면에서의 조도높이 따른 댐 붕괴파의 전파양상을 분석하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.85-101
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• 2020

The optimal parameters for the fluid-structure interaction analysis using the Smoothed Particle Hydrodynamics (SPH) for fluids and finite elements for structures, respectively, are explored, and the effectiveness of the simulations with those parameters is validated by solving several open surface fluid problems. For the optimization of the Equation of State (EOS) and the simulation parameters such as the time step, initial particle spacing, and smoothing length factor, a dam-break problem and deflection of an elastic plate is selected, and the least squares analysis is performed on the simulation results. With the optimal values of the pivotal parameters, the accuracy of the simulation is validated by calculating the exerted force on a moving solid column in the open surface fluid. Overall, the SPH-FEM coupled simulation is very effective to calculate the fluid-structure interaction. However, the relevant parameters should be carefully selected to obtain accurate results.

• Water for future
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• v.28 no.6
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• pp.119-131
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• 1995

Two-dimensional diffusion and kinematic hydrodynamic models have been studied for preparing the flood inundation map. The models have been tested by applying to one-dimensional dam-break problem. The results have good agreements compared with those of dynamic wave model. The diffusion wave model produces the mass conservation error close to zero. Floodwave analyses for two-dimensional floodplain with obstruction and channel-floodplain show both stable and efficient results. The model presented in this study can be used for flood inundation map and flood warning system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.3
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• pp.114-122
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• 2018

This paper introduces a non-hydrostatic wave model SWASH for simulating wave interactions with porous structures. This model calculates the flow in porous media based on volume-averaged Reynolds-averaged Navier-Stokes equations (VARANS) in ${\sigma}$-coordinate. The empirical coefficients of resistance used to account for the flow in a porous media often need to be measured or calibrated. In this study, the empirical resistance coefficients used in the model are calibrated and validated using laboratory experiments, involving dam-break flow through porous media, and solitary wave interactions with a porous structure. It is shown that the agreement between experimental and numerical results is generally satisfactory. It is also confirmed that non-hydrodynamic model, SWASH, is computationally much more efficient than the three-dimensional porous flow models based on VOF approach.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.550-554
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• 2009

본 연구에서는 댐 붕괴시 발생하는 홍수파가 건물군으로 이루어진 가상의 도시지역을 관통하면서 이동될 경우 시간에 따라 변화되는 특성을 수치적으로 분석하였다. 분석에 적용된 수치모형은 2차원 유한체적법과 불연속 흐름을 모의하기 위해 시간과 공간상으로 1차 정확도를 가진 HLLC 기법을 적용한 모형이다. 본 연구에서 적용된 가상의 도시지역은 Soares-Frazao와 Zech(2008)에 의해 수행된 수리모형실험에 근거하여 세 가지 case에 대해 구성하였다. 첫 번째 case(Case 1)는 25개의 건물로 구성된 정방형의 도시지역이 흐름에 직각으로 배열되어 있는 경우이며, 두 번째와 세 번째 case는 각각 흐름에 대해 $22.5^{\circ}$(Case 2)와 $45^{\circ}$(Case 3)로 경사진 경우이다. 세 경우에 대해 시간에 따른 홍수파의 변화양상을 수치적으로 분석하였으며, 첫 번째와 두번째 case에 대해 모의된 수위변화결과를 수리모형실험결과와 비교하여 모형의 적용성을 검증하였다. 검증결과 수치모형을 통해 계산된 수위변화는 수리모형실험결과와 비교적 일치하는 결과를 얻었다. 또한 본 연구에서는 도시지역의 조도계수(Manning계수: 0.01,015,$0.025sm^{-1/3}$)와 비구조적 격자시스템을 구성하는 격자수(T1: 19759개 요소, T2: 193859)에 따른 홍수파의 변화양상을 분석하였다.