• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.92-108
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• 2017

Present work shows a numerical method to analysis of interaction analysis between solitary wave and onshore bridge. Numerical simulation is carried out by TWOPM-3D (three-dimensional one-field model for immiscible two-phase flows), which is based on Navier-Stokes solver. To do this, the solitary wave is generated numerically in numerical wave channel, and numerical results and experimental results were compared and analyzed in order to verify the applicability of force acting on an onshore bridge. From this, we discussed precisely the characteristics of horizontal and vertical forces (uplift and downward forces) changes including water level and velocity changes due to the variation of solitary wave height, water depth, onshore bridge's location and type, and number of girder. Furthermore, It is revealed that the maximum horizontal and vertical forces acting on the girder bridge show different varying properties according to the number of girder, although each maximum force acting on the girder bridge is proportional to the increasement of incident solitary wave height, and the entrained air in the fluid flow affects the vertical force highly.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.166-179
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• 2018

This study aims at numerically investigating the water-surface characteristics such as wave height distribution depending on the current direction around the three-dimensional permeable submerged breakwaters in wave-current coexisting field which has not been considered in detail so far. In addition, the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy, which act as the main external forces of formation of salient, are also examined. For numerical analysis, olaFlow which is open source code of CFD was used and the numerical tests included different types of target waves, both regular waves and irregular waves. Numerical results indicated that wave height variation with wave following or opposing a current behind the submerged breakwater is closely related to turbulent kinetic energy. Furthermore, it was found that weaker longshore currents are formed under wave-current coexisting field compared to the non-current conditions, and transport flow is attenuated. As a result, it was possible to understand the influence of current existence and direction (following and opposing) on the formation of the salient formed behind the submerged breakwaters.

• 한국해양학회지
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• v.26 no.3
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• pp.204-222
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• 1991

The annual cycles of plant major nutrients and dissolved oxygen in a nutrients-rich semi-enclosed coastal inlet, chinhae Bay, of the southern coast of the Korean Peninsula are first presented. The water column of the bay is stratified during summer (April-late September) and well0mixed during winter (October-March). During the summer stratification period, dissolved oxygen contents exceed 400uM in the surface but diminish to less than 50uM in the near bottom waters, which often results in an anoxic environment in the inner part of Chinhae Bay. After the breakdown of the stratification in October, dissolved oxygen concentration remains undersaturated until February. The evidence of allochthonous input of N-nutrients throughout the year is readily seen in the water column: however. crude budget calculations show that the nutrients are efficiently utilized within the bay ecosystem, and that export of the nutrients from the bay to the shelf must be negligible. There is no sign of the enrichment of the nutrients in the water column. The eutrophication phenomenon sensu stricto is not observed in chinhae Bay. Using the standing stock of dissolved oxygen and estimation of the oxygen fluxes across the air-sea boundary, a benthic oxygen respiration rate during winter is estimated conservatively at 21-24 mmol Cm/SUP -2/d/SUP -1/. this oxygen respiration rate accounts for about 20% of the total phytoplankton production in winter.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.180-198
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• 2019

In recent years, countries like Europe and Japan have been involved in many researches on the Low-Crested Structure (LCS) which is the method to protect beach erosion and it is regarded as an alternative to the submerged breakwaters, and compiled its results and released the design manual. In the past, studies on LCS have focused on two-dimensional wave transmission and calculating required weight of armor units, and these were mainly examined and discussed based on experiments. In this study, three-dimensional numerical analysis is performed on permeable LCS. The open-source CFD code olaFlow based on the Navier-Stokes momentum equations is applied to the numerical analysis, which is a strongly nonlinear analysis method that enables breaking and turbulence analysis. As a result, the distribution characteristics of the LCS such as water level, water flow, and turbulent kinetic energy were examined and discussed, then they were carefully compared and examined in the case of submerged breakwaters. The study results indicate that there is a difference between the flow patterns of longshore current near the shoreline, the spatial distribution of longshore and on-offshore directions of mean turbulent kinetic energy in case of submerged breakwaters and LCS. It is predicted that the difference in these results leads to the difference in sand movement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.189-199
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• 2019

The purpose of this study is to derive spatial area(preventive zone) where the movement of livestock vehicles occurs frequently. For this purpose, this study used 6 periods facility entrance data provided by KAHIS. This data was converted into vehicle movement data between livestock facilities and aggregated into administrative district units. The R-mode factor analysis was performed on the constructed OD data, and the region extracted by the same factor was judged as one region. The results of the analysis are summarized as follows. First, the factor analysis of 6 periods data showed 16 ~ 18 factors, and the derived factors explained 63 ~ 68% of the total variance. Second, based on the factors that were derived, Jeonam coastal area, Jeonnam area, Jeonbuk area, Chungnam coastal area, Gyeongnam area, northern Gyeongbuk area, Yeongnam costal area were found to be stable, with little change over time. On the other hand, Chungbuk area, Gangwon area, Seoul metropolitan area are relatively volatile areas. Third, 13 areas were derived by combining data from six periods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.242-252
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• 2018

It is well known that an Oscillating Water Column Wave Energy Converter (OWC-WEC) is one of the most efficient wave absorber equipment. This device transforms the vertical motion of water column in the air chamber into the air flow velocity and produces electricity from the driving force of turbine as represented by the Wells turbine. Therefore, in order to obtain high electric energy, it is necessary to amplify the water surface vibration by inducing resonance of the piston mode in the water surface fluctuation in the air chamber. In this study, a new type of OWC-WEC with a seawater channel is used, and the wave deformation by the structure, water surface fluctuation in the air chamber, air outflow velocity from the nozzle and seawater flow velocity in the seawater channel are evaluated by numerical analysis in detail. The numerical analysis model uses open CFD code OLAFLOW model based on multi-phase analysis technique of Navier-Stokes solver. To validate model, numerical results and existing experimental results are compared and discussed. It is revealed within the scope of this study that the air flow velocity at nozzle increases as the Ursell number becomes larger, and the air velocity that flows out from the inside of the air chamber is larger than the velocity of incoming air into the air chamber.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.253-262
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• 2018

Oscillating Water Column (OWC) Wave Energy Converters (WEC) harness electricity through a Power-Take-Off (PTO) system from the induced-airflow by seawater oscillating inside a chamber. In general, an air chamber with a relatively small cross-sectional area is required compared to seawater chamber to obtain high-velocity air in the PTO system, and in order to simulate an accurate air flow rate in the air chamber, a three-dimensional study is required. In this study, the dynamic response of OWC-WEC that is equipped with the channel of seawater exchange for the case of irregular waves has been numerically studied. The open source CFD software, OLAFLOW for the simulation of wave dynamics to the openFOAM and FOAM-extend communities, was used to simulate the interaction between the device and irregular waves. Based on the numerical simulation results, we discussed the fluctuation characteristics of three dimensional air flow in the air-chamber, wave deformation around the structure and the seawater flow inside the channel of seawater exchange. The numerical results the maximum air flow velocity in the air-chamber increases as the Ursell value of the significant wave increases, and the velocity of airflow flowing out from the inside of air chamber to the outside is greater than the speed of flowing into the air chamber from the outside.

• Journal of Korean Port Research
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• v.11 no.2
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• pp.231-240
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• 1997

In the United States, a number of ocean outfalls discharge primary treated effluent into deep sea water and contribute for more efficient wastewater treatment. The long multiport diffuser connected by long pipe from a treatment plant discharge wastewater into deep water due to the steep slope of the sea bed. However, Plume discharged from the diffuser can have significant impacts on coastal communities and possibly immediate consequence on public health. Therefore, there have been growing interests about the dynamics of plume in the vicinity of the ocean outfalls. It is expected that the ocean outfall should be considered for more efficient and reliable wastewater treatments as soon as possible around coastal area in South Korea. A number of studies of plume ynamics have used various models to predict plume behavior. However, in many cases, the calculated values of plume behavior are in significantly poor agreement with realistic values. Therefore, in this study, it is recommended that improvements should be made in the application of the plume model to more simulate the actual discharge characteristics and ocean conditions. It should be noted that input parameters in plume models reflect realistic ocean conditions like waves as well as currents. In this study, as one of the new parameters, current and long wave-influenced plume rise and initial dilution have been taken into account by using simple linear wave theory under some specific assumptions for more reliable plume behavior description. Among the improved plume models approved by EPA (Environmental Protection Agency), the RSB(Roberts-Snyder-Baurngartner) and UM(Updated Merge) models were chosen for the calculation of plume behavior, and the variation calculated by both models on the basis of long period wave was compared in terms of plume rise and initial dilution.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.108-128
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• 2002

In order to investigate the ecological characteristics of phytoplankton communities around a nuclear power plant in Gori coastal waters of the South East Sea, Wolseong and Uljin coastal waters of the East Sea and Younggwang coastal waters of the Yellow Sea, the standing crops and chlorophyll-$\alpha$ concentrations of phytoplankton were studied during 1992~1996 and the relationships between standing crops and environmental variables were analyzed. The concentrations of nitrogenous nutrients were on average 0.101, 0.094, 0.072 and 0.108mg/$\ell$ and those of phosphorus were on average 0.007, 0.008, 0.006 and 0.009mg/$\ell$ in Gori, Wolseong, Uljin and Younggwang, respectively. The N:P ratios were highly variable, ranging from 3.2 to 57.3, from 3.1 to 109.0, from 2.6 to 102.0 and from 1.0 to 165.0 in Gori, Wolseong, Uljin and Younggwang, respectively. The concentrations of suspended solids were on average 18.7, 16.7, 11.6 and 52.7mg/$\ell$ and transparencies were on average 3.8, 5.4, 7.9 and 0.7 m in Gori, Wolseong, Uljin and Younggwang, respectively. Total standing crops of phytoplankton averaged 710,659, 687,508, 656,245 and 1,278,173cells/$\ell$ in Gori, Wolseong, Uljin and Yaunggwang, respectively. The standing crops of microplankton(>20${\mu}{\textrm}{m}$) averaged 357,546, 333,638, 276,407 and 592,975cells/$\ell$ those of nanoplankton(<20${\mu}{\textrm}{m}$) averaged 353,113, 353,870, 379,838 and 574,563cells/$\ell$ in Gori, Wolseong, Uljin and Younggwang, respectively. While standing crops of diatoms were averaged 282,009, 284,710, 238,758 and 574,563 cells/$\ell$, those of dinoflagellates were averaged 46,079, 35,401, 32,906 and 16,749 cells/$\ell$ in Gori, Wolseong, Uljin and Younggwang, respectively. The seasonal standing crops of diatoms in Gori, Wolseong and Uljin were higher in Spring than other seasons, but were lower in Summer than other seasons in Younggwang. The seasonal standing crops of dinoflagellates in Gori and Younggwang were higher in Summer than other seasons, but were higher in Autumn than other seasons in U]jin. Average of chlorophyll-$\alpha$ concentrations ranged from 2.16 to 4.28$\mu\textrm{g}$/$\ell$ in 4 study areas with the highest concentration occurred in Younggwang. Indices of species diversity ranged from 2.11 to 2.24 in 4 study areas. While community structures of phytoplankton were unstable during winter and stable during summer in Gori, Wolseong and Uljln coastal waters, those of phytoplankton were stable during winter and summer than during spring and autumn in Yaunggwang. The analysis results of Pearson product moment correlation coefficient between standing crops and environmental variables showed that distributions of standing crops were affected by transparencies, suspended solids, and some nutrient(N $O_3$$^{[-10]}$ -N, P $O_4$$^{3-}$-P), even though the degree of influences were a little different according to the season and the surveyed zone.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.166-173
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• 2010

In order to obtain the basic information for agricultural utilization of germanium (Ge), the growth characteristics, Ge uptake, and grain quality of rice plant (Hopyungbyeo) were investigated under different germanium ($GeO_2$, and commercial Ge) treatments in paddy field. Phytotoxicity was detected in $GeO_2$ treatment but not in commercial Ge treatment. The grain yield was greater in the order of control treatment > commercial Ge treatment > $GeO_2$ treatment. The dry weight was greater in order of control treatment > $GeO_2$ treatment ${\geq}$ commercial Ge treatment. The Ge content of leaf in $GeO_2$ treatment was 6 times (177 mg $m^{-2}$) higher than that in commercial Ge treatment. The Ge content in rice bran was not different in $GeO_2$, and commercial Ge treatments. The Ge contents of brown rice in$GeO_2$, and commercial treatments were 40.9, and 31.1 mg $kg^{-1}$, respectively. The Ge uptake rates in rice plant was higher in the order of leaf > rice bran > brown rice > stem > root. Under $GeO_2$, 15.56% of Ge absorbed into plant with 11.1% in leaf, 1.6% in stem, 0.03% in root, 2.2% in rice bran and 0.73% in brown rice. Under commercial Ge treatment, 5.19% of Ge absorbed into plant with 1.8% in leaf, 0.46% in stem, 0,01% in root, 2.2% in rice bran, and 0.71% in brown rice. Based on these results, the Ge contents in polished rice in commercial Ge treatment were higher than those in $GeO_2$ treatment. However, the Ge contents of rice grain (containing rice bran and polished rice) in $GeO_2$ treatment were higher than those in commercial Ge treatment.