• Journal of Environmental Science International
• /
• v.23 no.3
• /
• pp.409-431
• /
• 2014

In this study, the characteristics in the simulation of high-resolution coastal weather, i.e. sea surface wind (SSW) and significant wave height (SWH), were studied in a southeastern coastal region of Korea using the WRF and SWAN models. This analyses was performed based on the effects of various input factors in the WRF and SWAN model during M-Case (moderate days with average 1.8 m SWH and $8.4ms^{-1}$ SSW) and R-Case (rough days with average 3.4 m SWH and $13.0ms^{-1}$ SSW) according to the strength of SSW and SWH. The effects of topography (TP), land cover (LC), and sea surface temperature (SST) for the simulation of SSW with the WRF model were somewhat high on v-component winds along the coastline and the adjacent sea of a more detailed grid simulation (333 m) during R-Case. The LC effect was apparent in all grid simulations during both cases regardless of the strength of SSW, whereas the TP effect had shown a difference (decrease or increase) of wind speed according to the strength of SSW (M-Case or R-Case). In addition, the effects of monthly mean currents (CR) and deepwater design waves (DW) for the simulation of SWH with the SWAN model predicted good agreement with observed SWH during R-Case compared to the M-Case. For example, the effects of CR and DW contributed to the increase of SWH during R-Case regardless of grid resolution, whereas the differences (decrease or increase) of SWH occurred according to each effect (CR or DW) during M-Case.

• Journal of Ocean Engineering and Technology
• /
• v.29 no.4
• /
• pp.300-308
• /
• 2015

With the increases in oil and gas prices, and energy consumption, drillship construction has increased during the last decade. A drillship using a dynamic positioning (DP) system to maintain its position and heading angle during drilling operations. In addition, a drillship is equipped with a moonpool structure to allow its drilling systems to be operated in the midship section. A drillship for the North Sea is specially designed to endure harsh environmental loads. For safe operation in the North Sea, the drillship should have good motion response and robust hull strength. A break water should be considered on the bow and side deck to prevent the green water on deck phenomenon from incoming waves. In addition, the moonpool should be designed to reduce the speed loss and resonance motion. In this study, the hydrodynamic characteristics of a drillship for the North Sea were examined in relation to the motion, wave loads, green water, and moonpool resonance in the initial design stage.

• Journal of Navigation and Port Research
• /
• v.33 no.10
• /
• pp.703-707
• /
• 2009

In order to evaluate applicability of cylindrical slit type block breakwater to the field water, which was designed from the previous physical model study, it is analyzed the calmness of harbor area by the numerical model experiment. For a small fishery port in southern coast of Korea a SWAN model using the wave action balance equation was formulated. The reflection and transmission coefficients induced by the physical model test were introduced to the numerical model. The model response with cylindrical slit type breakwater was compared with the impermeable breakwater case and the possibility of water quality improvement through the water circulation by the new structure was investigated. For numerical simulation, parameters of deepwater design wave from the prediction report II for overall deepwater design wave by KORDI were used and wind parameters from the 50years return period observed for 37years(1970~2006) were adopted in the numerical model. The response of west breakwater in Mijo port applying the NE and NNE waves, which were dominant in this area, was analyzed. It was found that the transmission characteristic of designed cylindrical slit breakwater was well presented in the numerical model.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.24 no.3
• /
• pp.179-188
• /
• 2012

Performance analyses of vertical breakwaters were conducted for fictitiously designed breakwaters for various water depths to analyze the influence of climate change on the structures. The performance-based design method considering sea level rise and wave height increase due to climate change was used for the performance analysis. One of the problems of the performance-based design method is the large calculation time of wave transformation. To overcome this problem, the SWAN model combined with artificial neural network was used. The significant wave height and principal wave direction at the breakwater site are quickly calculated by using a trained neural network with inputs of deepwater significant wave height and principal wave direction, and tidal level. In general, structural stability becomes low due to climate change impacts, but the trend of stability is different depending on water depth. Outside surf zone, the influence of wave height increase becomes more significant, while that of sea level rise becomes negligible, as water depth increases. Inside surf zone, the influence of both wave height increase and sea level rise diminishes as water depth decreases, but the influence of wave height increase is greater than that of sea level rise. Reinforcement and maintenance policies for vertical breakwaters should be established with consideration of these results.

• Journal of Navigation and Port Research
• /
• v.43 no.6
• /
• pp.344-352
• /
• 2019

A coupled analysis was performed between the riser to develop oil and gas in ultra-deepwater and the moored floating body. In general, the safety of the riser is conservatively evaluated by considering the maximum offset excluding the coupled analysis with the floating body. In this study, the safety of the riser was analyzed by considering the coupled motion analysis of the moored floating body. The riser is considered steel lazy wave riser (SLWR) applied in the deep sea, and the floating body is determined to FPSO. The methodology was presented on coupled and uncoupled analysis. The coupled effects were analyzed according to the incident wave headings in intact and damaged conditions of mooring lines. The tension of mooring lines, the motion of the floating body, and riser responses were analyzed according to the loading conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.19 no.4
• /
• pp.313-319
• /
• 2007

Long term wave climate of both extreme and operational wave height is essential for planning and designing coastal structures. Since the availability of the field wave data for the waters around Korean peninsula is limited to provide a reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. In this paper, a set of deep water wave data obtained from KORDI(2003) were analyzed for extreme wave heights. These wave data at 67 stations off the Korean coast from 1979 to 1998 were arranged in the 16 directions. The probability distributions considered in this research were the FT-I and Weibull distribution. For each of these distributions, the method proposed by Goda(2004) was applied to estimate the parameters. For judgment of best fitting, MIR criterion proposed by Goda and Gobune(1990) was used. FT-I distribution which best fits to the 886 data, while Weibull(k=0.75) 81 data, Weibull(k=1.00) 105 data.