• Ocean and Polar Research
• /
• v.33 no.spc3
• /
• pp.397-407
• /
• 2011

To understand the vertical structure of ocean currents from raw data observed by lowered-ADCP (LADCP), these data require post-processing. Data were processed using Krahman's version 10.8 processing software based on Matlab. It is estimated the influence of auxiliary data affecting the processed current structure. The bottom-tracked velocities and the GPS information significantly contribute the offset on reference velocities in the bottom layer and barotropic ones in the middle layer, respectively. Good quality data can be obtained when LADCP is least tilted in pitch and roll during observation. In situ application of LADCP to the (northward) volume transports of Kuroshio in the East China Sea proved to be 24.8. Sv (= $1{\times}10^6m^3s^{-1}$) in October 2007, and 28.2 Sv in June 2008, respectively. The volume transport is relatively large over the continental slope when compared to the shelf or the deep sea.

• Journal of Environmental Impact Assessment
• /
• v.5 no.1
• /
• pp.31-45
• /
• 1996

This paper presents the results from a hydrodynamic model study to predict the impacts of coastal reclamation in Pusan harbor system using RMA2 which is a tidal flow model of the US Army Corps of Engineers' TABS-2 system. A finite element mesh was constructed and refined to cover the complicated geometry of Pusan harbor system and the proposed reclamation area. The model was calibrated to tidal elevations and currents measured during spring fall syzygys. Under the three different tidal conditions including summer winter syzygys, spring fall quarters, and summer winter quarters, the model predictions were compared with the field measurements both in tidal elevation and current. In all cases, there were excellent agreements between the model predictions and the field measurements. The validated model was then used to predict the changes in tidal current and elevation that might occur due to the coastal reclamation. It was predicted that there would be no change in tidal elevation of this system after the reclamation. In tidal current, however, discernible changes were predicted near the proposed reclamation area both in magnitude and direction.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.3 no.3
• /
• pp.216-224
• /
• 2011

In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995) and Larson and Kraus (2002). Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF) basin and the Hazaki Oceanographical Research Station (HORS). Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 1996.10a
• /
• pp.19-22
• /
• 1996

Extreme sea statistics and combinations of environmental events or response for structures are very important problem in performance evaluation and design of coastal and Offshore structures. A probabilistic method is developed that leads to the combination of Typhoon (Hurricane) or winter storm induces winds, waves, currents and surge for a generic site. The traditional recommendation for the fixed structures is a combination of the 100 years maximum wave height with the 100 years wind and current. (omitted)

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.30 no.3
• /
• pp.142-149
• /
• 1994

In order to investigate the environmental properties of set net grounds located in the coastal waters of Yeosu. The current in the vicinity of set net grounds was observed by drogue and current meter in 1990 and 1992. The results obtained are summarized as follows: The direction of tidal current at the north enterance of Yeosu bay was southerly in ebb and northwesterly in flood without the distiction of the neap tide and the spring tide. In spring tide the maximum Velocity of the tidal current was 68 cm/sec in ebb and 66 cm/sec in flood. In neap tide the maximum velocity of the tidal current was 37 cm/sec in ebb and 35 cm/sec in flood. And so the direction of residual current was the south ward mainly and 21 cm/sec. The direction of tidal current at set net fishing grounds was southwesterly in ebb and westerly or northwesterly in flood. Regardless of the distinction of neap and spring. The maximum velocity of the current in spring tide was 50 cm/sec in ebb and 40 cm/sec in flood and that in neap was 28 cm/sec in ebb and 25 cm/sec in flood. In spring tide the speed vector along the major axis of semidiurnal tide component was three times as large as diurnal tide. In neap tide, however, the speed vector was about 50% less then that in spring tide, and the semidiurnal tide and diurnal tide were equal in the size of current ellipse and the direction of major axis. The sea area had a southwesterly residual current. 11 cm/sec in spring tide and 7 cm/sec in neap tide. According to the result of drogue tracking, the vicinity of set net fishing ground had a southerly residual current which formed in Yeosu Bay and a weak westerly residual current toward Dolsando from Namhedo. Therefore, set net fishing ground in coastal water of Yeosu was distributed in boundary of inner water which formed from Seamjin river and offshore water supplied from the vicinity of Sorido and Yochido.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.13 no.4
• /
• pp.151-162
• /
• 1980

To clarify the dispersion of pollutants introduced in the coastal region, a series of current measurements, the drogue and drift bottle experiments as well as the dye diffusion experiments were carried out in Onsan Bay and in the coastal waters of Ubong-ri near Ulsan. In the southeastern coastal region of Korean peninsula, that is, in the outside of Onsan Bay, the flood tidal current flows south-south-westward, and the ebb current flows north-north-eastward at a maximum speed of 1.0-1.1 knots at spring tide. In an inlet south of Cape Ubong, an anticyclonic eddy of 1 km in diameter is usually formed during both flood and ebb flows. The tidal current predominates in Onsan Bay at around spring tide. The maximum speed around spring tide was observed to be approximately 0.14 knot, while it was slower than 0.1 knot and variable at neap tide when the wind drift current played an important role. The flood tidal current flows westward while the ebb flow flows eastward in the northern region of the bay. The flood tidal current in the southern region of the bay flows west-north-westward, while the ebb current east-north-eastward. Wind drift currents in the coastal region of southern Korea are generally deduced to be southward in winter, the monthly mean speed being approximately 0.1 knot. Dye solution released at the northwestern corner in Onsan Bay was transported by eastward ebb tidal current toward the mouth of the bay dispersing by the wind. The apparent diffusion coefficient at 150 minutes after release in the bay was calculated to be $4.4\times10^4\;cm^2.sec^{-1}$, whereas that in the anticyclonic eddy was more or less smaller.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.512-515
• /
• 2005

The Korean peninsula has a number of coastal sites where the rhythmic rising and lowering of water surface due to tides result in strong tidal current. The kinetic energy of these currents can be efficiently exploited by using tidal current turbines. The pilot tidal current power plant is to be constructed at the Uldolmok between Chindo and Haenam. Extensive coastal engineer ing research works have been carried out. This paper describes some observation results of field campaign, design of the supporting structure of a pilot plant of 1,000kW and a future tidal current power plant and so on.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.5 no.2
• /
• pp.76-83
• /
• 1993

In this study, an approximate method for calculating the directional spectrum of waves encountering a current in shallow water is developed. The wave trains in tile directional spectrum are assumed to be linear and Gaussian; development of the spectrum requires that the waves also be short crested. The Miche's breaking criterion is imposed to determine the upper limit of wave height and to establish an expression for the breaking wave elevation in terms of the ideal wave's elevation and the second time derivative of wave elevation. Two examples are given; one for a Wallops directional spectrum encountering a shear current and another with an upwelling current.

• Journal of Ocean Engineering and Technology
• /
• v.29 no.5
• /
• pp.366-372
• /
• 2015

Ocean energy is one of the most promising renewable energy resources. In particular, South Korea is one of the countries where it is economically and technically feasible to develop tidal current power plants to use tidal current energy. In this study, based on the design code for HARP_Opt (Horizontal axis rotor performance optimizer) developed by NREL (National Renewable Energy Laboratory) in the United States, and applying the BEMT (Blade element momentum theory) and GA (Genetic algorithm), the optimal shape design and performance evaluation of the horizontal axis rotor for a 200-kW-class tidal current turbine were performed using different numbers of blades (two or three) and a pitch control method (variable pitch or fixed pitch). As a result, the VSFP (Variable Speed Fixed Pitch) turbine with three blades showed the best performance. However, the performances of four different cases did not show significant differences. Hence, it is necessary when selecting the final design to consider the structural integrity related to the fatigue, along with the economic feasibility of manufacturing the blades.

• Geosciences Journal
• /
• v.22 no.6
• /
• pp.989-1000
• /
• 2018

The provenance of the Central Yellow Sea Mud (CYSM) in the Yellow Sea has been attracted a great deal of attention over the last three decades, but a consensus is not yet reached. In this study, 101 surface sediment samples collected from the CYSM were investigated to determine provenance and transport mechanisms in the area using the clay minerals and major element components. The Huanghe sediments are characterized by higher smectite, but the Changjiang sediments are more abundant illite contents. Western Korean rivers contain more kaolinite and chlorite than do Chinese rivers. The Chinese rivers have higher $Fe_2O_3$, MgO, and CaO than the Korean rivers at the same $Al_2O_3$ concentration. Therefore, the clay minerals and major element concentrations can be useful indicator for the source. Based on our results, we suggest that the surface sediments in CYSM were composed mainly of Changjiang sediments, mixed a partly with sediments from the Huanghe and the western Korean rivers. Although the northwestern part of CYSM is proximate to the Huanghe, the contents of smectite and CaO were extremely low. It could be evidence that the Huanghe materials do not enter directly into the CYSM due to the Shandong Peninsula Front. Considering the oceanic circulation in the Yellow Sea, the Changjiang sediments could be transported eastward with the Changjiang Diluted Water and then mixed in CYSM via the Yellow Sea Warm Current (YSWC). Huanghe sediments could be provided by coastal currents (Shandong Coastal Current and Yellow Sea Coastal Current) and the YSWC. In addition, sediments from western Korean rivers might be supplied into the CYSM deposit via the Korean Coastal Current, Transversal Current, and YSWC.