• Ecology and Resilient Infrastructure
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• 제5권4호
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• pp.276-284
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• 2018

하단배출 형태의 연직수문을 대상으로 퇴적토 배출특성에 따른 두부침식 거리비, 퇴적토 이동거리와 이동량을 분석하기 위해 수리 모형실험과 차원해석을 수행하였다. Froude 수와 배출특성의 상관관계를 도식화하고, 퇴적토 배출특성을 지배하는 무차원 매개변수에 의한 다중회귀식을 제안하였다. 두부침식거리, 퇴적토 이동거리와 이동량에 대한 각 다중회귀 분석식의 결정계수는 각각 0.618, 0.632, 0.866으로 높게 나타났다. 개발한 퇴적토 배출특성식의 사용성을 평가하기 위해 실제 측정값과 회귀분석식에 의해 계산된 값의 95%의 예측 신뢰구간 분석을 수행하였고, 두부침식거리, 퇴적토 이동거리와 이동량에 대한 예측의 정확도 분석차원의 NSE (Nash-Sutcliffe Efficiency), RMSE (root mean square)와 MAPE (mean absolute percentage error)는 적절한 것으로 판단되었다.

• 한국환경과학회지
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• 제13권3호
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• pp.263-277
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• 2004

The purpose of this study is to analyze the characteristics of riverbed variation due to the sediment protection weir located on the estuary of the main stream of Taehwa river using I-D finite difference model, HEC-6 model, and the followings are the results of estimating sediment transport rate, amount of scour or deposition, and accumulated amount of deposit according to before and after of the sediment protection weir removal with various flow rates in the channel. Ackers-White transport function produced the greatest sediment transport rate while Meyer-Peter showed the smallest sediment transport rate at the most down stream area of the watershed through the sediment transport rate analyses for various flow rates according to the existence or nonexistence of the sediment protection weir. Toffaleti's and Colby transport function were closest to the average value, and the difference among the results of the sediment transport functions showed up to 8～9 times. Duboy's transport function produced the greatest riverbed variation while Toffaleti's showed the smallest variation through the riverbed variation analyses according to the existence or nonexistence of the sediment protection weir. Yang's was closest to the average value, and the difference among the results of the riverbed variation analyses ranged from 1.4 times to 11 times. It is thought that a sediment transport function must be selected very carefully with respect to the criteria of sediment yield estimation because the analysis results of the sediment transport rate and riverbed variation according to flow rates showed significant differences among the sediment transport functions, and the differences of sediment transport rate and riverbed variation according to the various sediment transport functions decreased as the flow rate increased.

• International Journal of Ocean System Engineering
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• 제2권1호
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• pp.1-7
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• 2012

The cross-shore sediment transport in a coastal region causes the important changes in beach morphological properties. The accurate estimation of the cross-shore sediment transport is important for the designing of the marine structures such as seawalls, jetties, breakwaters etc, and the preventing coastal erosion and accretion due to on-off shore sediment transportation. In this study, the experiments on cross- shore sediment transport carried out in a laboratory wave channel for initial beach slopes of 1/8, 1/10 and 1/15. Using the regular waves with different deep-water wave steepness generated by a pedal-type wave generator, the geometrical characteristics of beach profiles under storm conditions and the parameters affecting on-off shore sediment transport are investigated for the beach materials having medium diameters of $d_{50}$=0.25, 0.32, 0.45, 0.62 and 0.80 mm. The experimental results obtained from this study compared with previous experimental work and found to be of the same magnitude as the experimental measurements and followed the expected basic trend.

• Ocean Systems Engineering
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• 제6권1호
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• pp.61-97
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• 2016

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.277-286
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• 2013

Cross-shore sediment transport is very important factor in the design of coastal structures, and the beach profile is mainly affected by a number of parameters, such as wave height and period, beach slope, and the material properties of the bed. In this study cross-shore sediment movement was investigated using a physical model and various offshore bar geometric parameters were determined by the resultant erosion profile. The experiments on cross- shore sediment transport carried out in a laboratory wave channel for initial base slopes of 1/8, 1/10 and 1/15. Using the regular waves with different deep-water wave steepness generated by a pedal-type wave generator, the geometrical of sediment transport rate and considerable characteristics of beach profiles under storm conditions and bar parameters affecting on-off shore sediment transport are investigated for the beach materials with the medium diameter of $d_{50}$=0.25, 0.32, 0.45, 0.62 and 0.80 mm. Non-dimensional equations were obtained by using linear and non-linear regression methods through the experimental data and were compared with previously developed equations in the literature. The results have shown that the experimental data fitted well to the proposed equations with respect to the previously developed equations.

• 한국해안해양공학회지
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• 제14권3호
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• pp.201-208
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• 2002

천해조가 발달된 하구에서의 소류사 이동 특성에 관한 선행연구에 이어 본 논문에서는 전과 동일한 하구 부유사 이동 특성을 규명하였다. 소류사 이동에 비해 다소 복잡한 양태로 발생하는 부유사 이동에 관한 수치실험을 통해 turbidity maximum형성과 변이에 관련된 기존 연구결과를 재확인할 수 있었으며. 천해조를 하류경계조건에 포함시키는 것이 소류사의 경우와 마찬가지로 매우 중요함을 확인할 수 있었다. 또한 금강하구와 영산강하구에서의 소류사 및 부유사 이동특성의 차이점 뿐 아니라 창낙조우세와 고저조우세의 차이점도 규명할 수 있었다. 특히, 영산강하구의 경우 조간대 발달로 인해 낙조우세가 심화됨에 따라 소류사와 부유사가 서로 반대 방향으로 이동함에 의해 현재와 같이 조간대가 유지되고 있음을 규명하였다.

• Ecology and Resilient Infrastructure
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• 제5권4호
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• pp.246-256
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• 2018

하단배출 형태의 연직수문에서의 퇴적토사 이동을 수반한 유량계수, 수력도약 높이, 수력도약 길이의 수리특성을 분석하기 위해 수리 모형실험과 차원해석을 수행하였다. Froude 수와 수리특성의 상관관계를 퇴적토 이동 유무에 따라 도식화하고, 무차원 매개변수와 수리특성의 상관성을 분석하고 다중회귀분석식을 개발하였다. 퇴사의 이동을 수반한 수리특성은 퇴적토의 이동이 없을 경우와는 다른 양상을 확인하여 퇴적토 이동을 특성을 나타낼 수 있는 변수의 도입이 필요함을 확인하였다. 유량계수, 수력도약 높이와 수력도약 길이에 대한 각 다중회귀분석식의 결정계수는 유량계수 0.749, 수력도약 높이 0.896, 수력도약 길이 0.955로 높게 나타났다. 개발한 수리특성식의 적용성을 평가하기 위해 실제 측정값과 회귀분석식에 의해 계산된 값의 95%의 예측구간 분석을 수행하였고, 유량계수, 수력도약 높이와 길이에 대한 예측의 정확도 분석차원의 NSE (Nash-Sutcliffe Efficiency), RMSE (root mean square)와 MAPE (mean absolute percentage error)는 적절한 것으로 판단되었다.

• Water Engineering Research
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• 제6권1호
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• pp.17-30
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• 2005

The bed evolution of the stretch of the River Rhine between km-812.5 and km-821.5 is characterised by general bed degradation as a result of the river training works and dredging activities of the last two centuries. The degradation of the river bed affects the water levels, and so the navigation conditions. To combat the erosion of the river bed with the aim to keep up the shipping traffic and to avoid the ecological system damages due to water level reductions, sand-gravel-mixtures were added to the river (so called artificial grain feeding activities). This paper presents the results of an application of a graded sediment transport model in order to study morpholodynamical characteristics due to artificial grain feeding activities in the river stretch. The finite element code TELEMAC2D was used for flow calculation by solving the 2D shallow water equation on non-structured grids. The sediment transport module SISYPHE has been developed for graded sediment transport using a multiple layer model. The needs to apply such graded sediment transport approaches to study morphological processes in the domain are discussed. The calculations have been carried out for the case of middle water flow and different size-fraction distributions. The results show that the grain feeding process could be well simulated by the model.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.365-370
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• 2000

Sea dike construction for the tidal flat reclamation works in estuary and coast may change the characteristics of tidal motion and wave conditions in the region. In turn, a new hydraulic condition provides the impacts on sediment transport pattern and forms a new morphological environment. Also, morphological changes during the closure works of sea dike are closely related with a safy of sea dike. Therefore, the prediction of morphological changes is required secure the safe closure work and the economic design of sea dikes. To investigate morphological changes due to sea dike construction, hydrodynamic changes of tides and waves have to be evaluated, then sediment transport and sea bottom changes are computed. Mathematical modelling is required for representation of interrelation of tidal motion, wave and sediment transport. In this study, numerical model MORSYS is applied to compute the hydrodynamics and morphological changes around the closure gap for Saemankuem dike. This model allows a flexible integration of the module for waves, currents, sediment transport and bottom changes.

• 대한토목학회논문집
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• 제31권3B호
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• pp.205-209
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• 2011

배수관로 내의 토사퇴적으로 인한 통수능 저하는 도시홍수의 주요 발생 원인으로 배수관로의 효율적 유지관리는 도시홍수 예방에 대단히 중요하다. 따라서 본 연구에서는 만관 원형관로에서의 토사이송 실험을 실시하고 배수관로 내에서 일어나는 유사이송 형태, 흐름의 저항 및 유사량 등 수리학적 특성을 분석함으로써 관로의 효율적 유지관리를 위한 기초 자료를 제시 하였다. 본 실험은 길이 8 m, 관경 60 mm의 수평 관로와 유사 공급장치로 구성된 모형장치을 통하여 실내실험을 수행하였다. 실험장치는 최대 $30m^3/hr$ 규모의 유량 순환시스템을 갖추고 있으며 관로 상류부에 5 g/s~19 g/s 규모의 유사 공급 장치와 함께 관로 끝부분에 유사 회수시스템을 갖추고 있다. 본 연구 수행 결과 통수단면의 평균유속(U), 점성계수(${\mu}$), 단위 폭당 소류사량($q_b$), 평균입경($d_{50}$), 수중유사단위중량(${\gamma}^{\prime}_s$)를 주요 인자로 하는 두 개의 무차원 변수를 이용하여 압력 원형관로 내 토사이송을 예측하는 공식을 제안하였으며 이들 무차원 변수 간에는 선형 상관관계가 있음을 확인하였다.