• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.373-380
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• 2018

We present the peridynamic dynamic fracture analysis to solve impact fracturing of multilayered glass impacted by a high-velocity object. In the most practical multilayered glass structures, main layers are glued by thin elastic masking films. Thus, it is difficult and expensive to construct the numerical model for such a multilayered structure. In this paper, we employ efficient numerical modeling of multilayered structures with a nonlocal ghost interlayer model in which ghost particles are distributed between main layers and they are interacting with each other in peridynamic way. We also consider a simple nonlocal contact condition in peridynamic frameworks to solve impact and penetration of the high-velocity impactor to the multilayered structure. Finally we can confirm the fracture capabilities of the method using a multilayered glass model in which 7 glass layers and a single elastic backing layer are affixed by polyvinyl butyral films.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.79-93
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• 2008

Water quality simulations on the Saemangeum inner reservoir have been carried out using EFDC model to understand water quality variations caused by abrupt physical changes due to closing of tidal barrier. According to hydrodynamic simulation, model reproduces not only outer regional dynamics but also inner superelevation very well. Calibration and verification of water quality models accomplished using observed data taken before closing. Also sensitivity tests regarding riverine discharges and tidal flats were done. Due to enlarging of always wet zone caused by super elevation on inner tidal flats, predicted DO decreases at that region as a result of SOD. Moreover shrink of mixing zone after closing of dike causes deteriorating of water quality showing DO as 2 mg/L during summer at Mangyeong and Dongjin estuaries, however it does not spread to middle part of the reservoir. Vertical stratification occurs after closing and shows vertical differences in DO concentration at least 6 mg/L to 7 mg/L in summer season. Most part of the reservoir is getting stratified and it leads to an oxigen deficit zone near bottom.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.3
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• pp.177-185
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• 2000

The adjoint method is a method of data assimilation to improve the model results by seeking for model parameters that minimize the cost function and satisfy the governing equations of a model simultaneously. An adjoint package was set up for the two-dimensional linear tidal model and was applied to an idealized domain for an optimal estimation of the open boundary conditions. The assimilating data were selected from the results of forward modeling. Attention is paid on the response of the adjoint package to weighting parameters, the importance of initial estimates of model parameters and the applicability of the adjoint package to the case with varying depth. A procedure to determine optimal weight is presented based on the relationships between weights and other factors.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.241-248
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• 2010

This paper deals with the performance analysis and design of the Darrieus-type vertical axis turbine to evaluate the effect of key design parameters such as number of blade, blade chord, pitch and camber. The commercial CFD software FLUENT was employed as an unsteady Reynolds-Averaged Navier-Stokes (RANS) solver with k-e turbulent model. Grid system was modelled by GAMBIT. Basic numerical methodology of the present study is appeared in Jung et al. (2009). Two-dimensional analysis was mostly adopted to avoid the barrier of massive calculation required for parametric study. It was found that the highly efficient turbine model could be designed through the optimization of design parametrrs.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.62-62
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• 2011

한강하구지역의 강화해협은 한강, 임진강과 예성강의 강물이 흘러들어오는 하구형 수로로서 폭이 좁고, 유속이 매우 빠른 특성을 갖는다. 또한 조류(潮流)의 영향을 강하게 받아 상당량의 유량을 경기만으로 내보내고, 한강의 상류로부터 유입되는 상당량의 물질이 하구로 운반되어 침전하여 쌓이거나 하류의 외해로 배출하는 역할을 한다. 본 연구에서는 한강하류부에 위치한 강화해협의 유 무에 따른 한강과 임진강의 흐름특성 변화를 분석하였다. 수치모의를 위해 복잡한 하구지역의 물의 흐름해석이 가능한 일차원적인 모델링 도구인 MIKE 11 모형을 이용하여 정류 및 부정류 해석을 실시하였다. 상류경계조건은 홍수 시 방류량이 크게 증가하는 홍수기 유량과 조위의 영향을 많이 받는 평수기 시 유량으로 설정하였고, 하류경계조건은 평수기를 비롯하여 홍수기에도 임진강과 한강의 유량에 영향을 미치는 서해 조위로 설정하였다. 강화해협의 폐쇄에 따른 수위 변화의 영향은 홍수기 시 실제 강우 사상을 모의 하였을 때 최대 8.21% 수위가 상승하였으며, 200년 빈도 계획홍수량을 모의한 결과로는 정류 해석의 경우 최대 8.25%의 변화율을 보였고, 부정류 해석의 경우 최대 13.08%의 변화율을 보였다. 평수기는 창조기에 수위 변화가 적었던 반면 낙조기에는 창조기에 비해 수위 변동이 심하게 일어나는 것으로 나타났다. 추후 강화해협 뿐만 아니라 해양생태계의 중요한 가치를 지니고 있는 한강하구의 다른 수로에 의한 영향을 분석함으로써 수로의 중요성을 평가하고, 2차원 수치해석 등을 통한 다양한 분석을 실행하여, 홍수 및 해양환경 훼손으로부터 하구 환경을 보호하는 보다 정량적인 대응체계가 정립되어야할 것으로 사료된다.

• 한국해양학회지
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• v.29 no.2
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• pp.83-94
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• 1994

Two-dimensional tidal and tidal residual currents in Chinhae Bay are investigated by field observations, hydraulic and numerical experiments. The results of hydraulic and numerical model experiments roughly coincide with the field measurements. Maximum tidal currents during the spring and neap tides in Kaduk and Kyunnaeryang channel and the central channel of Chinhae Bay are strong as 90 to 110 and 30 to 40 cm/s respectively, and strong tidal residual currents having numerous eddies take place. Maximum tidal currents during the spring and neap tides in the western and northern parts of the bay are weak as below 30 and 10 cm/s respectively, and also tidal residual currents are relatively weak. Tidal residual currents in the northern part of Kajo-do go toward the north, whereas the currents in the southern part move down the bay, and the currents rotating clockwise occur around Bu-do. The surface currents in the bay depend strongly on the wind and river inflow, and such phenomena are more remarkable during he neap tide than the spring tide.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.760-769
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• 2023

A numerical simulations were performed to investigate the storm surge during the passage of Typhoon Maemi on the coast of Busan. The typhoon landed on the southern coasts of Korean Peninsula at 21:00, September 12, 2003 with a central pressure of 950 hPa, and the typhoon resulted on the worst coastal disaster on the coast of Busan in the last decades. Observed storm surges at Busan, Yeosu, Tongyoung, Masan, Jeju and Seogwipo harbors during the passage of the typhoon were compared with the computed data. The simulated storm surge time series were in good agreement with the observations. The simulated peak storm surges were estimated to be 230 cm at Masan harbor, 200 cm at Yeosu harbor and Tongyoung harbor, and 75 cm at Busan harbor. The computed storm surges along the east coast of Busan measure 52 to 55 cm, exhibiting a gradual reduction in surge height as one moves further from the coast of Busan. Therefore, coastal inundation due to the storm surge in the semi-enclosed bay can induce great disasters, and the simulated results can be used as the important data to reduce the impact of a typhoon-induced coastal disaster in the future.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.286-296
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• 2016

Offshore CCS technology is to transport and inject $CO_2$ which is captured from the power plant into the saline aquifer or depleted oil-gas fields. The more accumulated injected $CO_2$, the higher reservoir pressure increases. The increment of reservoir pressure make a dramatic change of the operating conditions of transport and injection systems. Therefore, it is necessary to carefully analyze the effect of operating condition variations over the injection period in early design phase. The objective of this study is to simulate and analyze the $CO_2$ behavior in the transport and injection systems over the injection period. The storage reservoir is assumed to be gas field in the East Sea continental shelf. The whole systems were consisted of subsea pipeline, riser, topside and wellbore. Modeling and numerical analysis were carried out using OLGA 2014.1. During the 10 years injection period, the change of temperature, pressure and phase of $CO_2$ in subsea pipelines, riser, topside and wellbore were carefully analyzed. Finally, some design guidelines about compressor at inlet of subsea pipeline, heat exchanger on topside and wellhead control were proposed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.15 no.3
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• pp.97-109
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• 2010

This study analyzed stratification and destratification processes in the Kangjin Bay (KB), South Sea, Korea, driven by the Nam Gang Dam water discharge based on numerical modeling experiments. Model performances were evaluated in terms of skill scores for elevation, velocity, temperature and salinity, with scores mostly exceeding 90%. The models reproduced the tidal current, density-driven and wind-driven current. The stratification by fresh water input and destratification by the wind mixing was assessed in terms of the characteristic Richardson number (Ri) in that Ri increased from 0 to 7~20 during the Dam water discharge period, while vertical mixing and destratification followed by the typhoon passage showed Ri, 0 to 2.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.5
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• pp.223-233
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• 2018

The predictability of winter storm waves using KMA's operational wind forecasts has been studied to predict wind waves and swells in the East coast of Korea using SWAN. The nested model were employed along the East coast of Korea to simulate the wave transformation in the coastal area and wave dissipation term of whitecapping is optimized to improve swell prediction accuracy. In this study, KMA's operational meteorological models (RDAPS and LDAPS) are used as input wind fields. In order to evaluate model accuracy, we also simulate wind waves and swells using ECMWF reanalysis and KIOST WRF wind and they are compared with the KMA's operational wave model and the wave measurement data on the offshore and onshore stations. As a result, it has the lowest RMSE and the highest correlation coefficient in the onshore when the input wind fields are KMA's operational meteorological forecasts. In the offshore, all of the simulate results shows good agreements with similar error statistics. It means that it is very feasible to use SWAN model with the modified whitecapping factor and KMA's operational meteorological forecasts for predicting the wind waves and swells in the East coast of Korea.