• ALGAE
• /
• v.25 no.1
• /
• pp.37-44
• /
• 2010

A tide-simulating apparatus was developed for culturing marine macroalgae. The objective of this study was to introduce a novel tide-simulating apparatus that can simulate a diurnal or semi-diurnal tidal cycle in the laboratory. In this apparatus, the seaweeds are move up and down and the water level remains the same during the simulated tidal cycle. The apparatus consists of 18 cylindrical culture tanks (3 blocks $\times$ 6 culture tanks) with 12 cm diameter and 24.5 cm long containing up to 2.5 L of seawater. There is a horizontal plate which covered all 18 culture tanks, and it is raised and lowered by a programmable motor that can regulate exposure time. In one application, seaweeds are attached to braided twine hung on Plexiglas air-tubing. The air-tubing is attached to a lid that is set on a horizontal plate. This apparatus is made of colorless Plexiglas to maximize light transmittance. This apparatus is easily disassembled and transportable to any indoor laboratory, wet laboratory, greenhouse, etc. This apparatus also offers considerable flexibility in terms of design. The size of culture tank can be redesigned by either increasing the height of cylinder or/and using a different diameter of cylindrical Plexiglas, therefore, larger/taller thalli can be cultivated. Growth rates of three eulittoral Porphyra species from different tidal elevations have been compared using this device.

• Ocean and Polar Research
• /
• v.41 no.3
• /
• pp.193-202
• /
• 2019

There have been various approaches for efficiency improvement of a Darrieus tidal stream turbine after it was introduced as an alternative of horizontal axis turbines. Among the approaches, the researches on the interaction effect of dual configuration were conducted. In this study, a dual Darrieus turbine with a coupling mechanism was proposed for investigating the interaction effect. Also, the effect of bi-directional tidal stream was analyzed with prototype fabrication, apparatus set-up and experiment conduction in indoor and offshore facilities. As the results of the experiments, the dual turbine in case of counter-rotation and inflow between the turbines improved efficiencies by 9.5% and 11.31%, respectively, as compared to the single turbine. Also, the dual turbine in case of the inflow improved efficiencies by 9.4% and 16.62%, respectively, as compared to that in case of outflow between the turbines which represented the case of 180 degrees change of flow direction after slack water. Therefore, the proposed dual turbine showed the advantage in terms of the efficiency as compared to the single turbine and the effect level of the slack water on the performance of the dual turbine was investigated.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.6
• /
• pp.552-561
• /
• 2023

The seafloor topography of Gomso Bay on the west coast of Korea was investigated using subtidal bathymetry and tidal-flat altimetry. Gomso Bay consists of 80% tidal flats and 20% subtidal zone, and is divided into an outer bay and an inner bay by the Jujincheon esturary channel. The outer bay tidal flat, has few tidal channels, has a concave topographic profile, and is characterized by the development of chenier and intertidal sand bars, giving it the appearance of gently sloping, dissipative beaches. The inner bay tidal flat has wide upper and middle tidal flats with a well-developed tidal channel system without cheniers. Moreover, the topographical cross-section between these tidal channels is convex upward, and shows the characteristics of a depositional environment greatly influenced by tidal channels and tidal action. An analysis of the horizontal movement of the tidal flat environment over the past 37 years investigating changes in the iso-depth lines in the Gomso-Bay tidal flat between 1981 and 2018 revealed that the Gomso-Bay tidal flat retreated gradually landward. As a result of analyzing the erosion and sedimentation characteristics of Gomso Bay, assuming that most of the water depth changes were due to changes in the elevation of the sea floor and sea level, an average of 1 cm (0 mm/y) of sediment was eroded in the outer bay over the past 37 years (1981-2018), In the inner bay, an average of 50 cm (14 mm/y) was deposited. Notably, the high tidal flats of the outer bay were largely eroded. Monitoring photographs of the coast showed that most of the erosion of the high tidal flats in the outer bay occurred in a short period around 1999 (probably 1997-2002), and that the erosion resulted from the erosion of sand dunes and high-tide beaches caused by temporarily greatly raised high tide levels and storms.

• 한국해양학회지
• /
• v.29 no.3
• /
• pp.278-286
• /
• 1994

Tidal sand ridges, which develop in Kyeonggi Bay generally parallel to the direction of tidal current on the sea bottom are also well shown in seismic profiles, surface and core samples were obtained from sand ridge field near the Palmi Do for the study of origin and sedimentary environments of these sand ridges. Sand ridge field near Palmi Do can be divided into 3 seismic units(unit A, B, C), and each unit has one sand ridge(ridge A, B, C), Ridge A that shows clinoform prograding southeastwards is generally parallel with tidal current trending northeast to southwest(40$^{\circ}$). It means that sand ridge is migrating to southward. Unit B includes a sand ridge and a channel fill structure in seismic profiles. Compared with ridge A, ridge B has similar direction, magnitude and internal reflectors. So ridge B developed in the similar sedimentary environments to ridge A about 10 m lower than present sea level. As the rise of sea level, channel fill structure formed as the deposit of fine sediments with the shape of conformable bedding or horizontal bedding.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.2
• /
• pp.126-132
• /
• 2010

An approach to calculating expected damage of breakwater assisted by artificial neural network was developed. Wave height in front of a breakwater was predicted by a trained artificial neural network with inputs of wave height in deep ocean and tidal level. Prediction results by the neural network can be comparable to that by professional numerical model for wave transformation. Using the wave prediction neural network, it was very easy and fast to obtain a number of significant waves at breakwater and finally analysis time for expected damage can be shortened. In addition, the effect of considering tidal level in the calculation of expected damage was revealed by comparing the expected damages with and without tidal variation. Therefore, it was pointed out that tidal variation should be considered to improve prediction accuracy.

• Geomechanics and Engineering
• /
• v.27 no.6
• /
• pp.561-571
• /
• 2021

Cofferdams made of teel sheet piles are commonly utilized as support structures for excavation of sea-crossing bridge foundations. As cofferdams are often subject to tide variation, it is imperative to consider potential effects of tide on stability and serviceability of sheet piles, particularly, ultralong steel sheet piles (USSPs). In this study, a real USSP cofferdam constructed using new construction technology in Nanxi River was reported. The design of key parts of USSP cofferdam in the presence of tidal action was first introduced followed by the description of entire construction technology and associated monitoring results. Subsequently, a three-dimensional finite-element model corresponding to all construction steps was established to back-analyze measured deflection of USSPs. Finally, a series of parametric studies was carried out to investigate effects of tide level, soil parameters, support stiffness and construction sequence on lateral deflection of USSPs. Monitoring results indicate that the maximum deflection during construction occurred near the riverbed. In addition, measured stress of USSPs showed that stability of USSP cofferdam strengthened as construction stages proceeded. Moreover, the numerical back-analysis demonstrated that the USSP cofferdam fulfilled the safety requirements for construction under tidal action. The maximum deflection of USSPs subject to high tide was only 13.57 mm at a depth of -4 m. Sensitivity analyses results showed that the design of USSP cofferdam system must be further improved for construction in cohesionless soils. Furthermore, the 5th strut level before concreting played an indispensable role in controlling lateral deflection of USSPs. It was also observed that pumping out water before concreting base slab could greatly simplify and benefit construction program. On the other hand, the simplification in construction procedures could induce seepage inside the cofferdam, which additionally increased the deflection of USSPs by 10 mm on average.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.13 no.3
• /
• pp.53-63
• /
• 2010

The global sea level rise has an effect on eco-environmental change by the inundation and erosion in the coastal area. Forecasting model on the change of morpho-ecological environments by the sea level change will give us information for coastal area management by predicting environmental changes of the up-coming future. This research aimed to foresee eco-environmental changes by the sea level rise in coastal area. Prediction model used SLAMM model developed to forecast coastal changes by IPCC scenario. The model predicted centennial environmental changes in the mouth of Han river and Nakdong river, Suncheon and Hampyeung bay as case areas. To sum up the research findings, in the estuary of the Han river, tidal flat was gradually disappeared from the year 2075, scrubmarsh and saltmarsh belts were developed. In the Nakdong River estuary, scrubmarsh was decreased from the year 2025, tidal flat was deposited from the year 2050, and also, the Gimhae plain was partially inundated, and wetlands were formed. In the Hampyeung bay, saltmarsh was deposited in the year 2025, tidal flat expanded until 2050 was partially submerged after that time. Tidal flat of Suncheon bay was disappeared by the inundation after 2025, and saltmarsh was developed in the embayment.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.251-252
• /
• 2008

Si-Hwa tidal power station is using difference of the ebb and flow. The active power is dependent on up and down sea water level but if it is drastically changed because of a typhoon or waves the generator terminal voltage and active power is changed that is a chief cause of power station unstability. Therefore this paper arrange a present state of power or frequency fluctuation and generator terminal phase difference in case of occurrence a drastic change of sea water level.

• Journal of the Korean earth science society
• /
• v.23 no.7
• /
• pp.565-574
• /
• 2002

Based on previous investigations of aerial photographs and topographical surveys, this study focuses on the sedimentologic features of the Daebudo area including sedimentation processes, sedimentary facies and hydrologic conditions of the erosional coast. A total of 137 surface sediments and one core (by hand auger) sediment were obtained to interpret the depositional environment of the erosional coast in the macro-tidal coast. Surface sediments are distributed from sandy gravel (sG) to silt (Z). Textural parameters are characterized not only by coarse, poorly sorted, positive skewed and multi-modal distribution in the supra-tidal flat, but also finer, relatively well-sorted, symmetric distribution in the intertidal flat. According to the C/M diagram, sediment transport modes of study area are characterized by the mixed mode of suspension and bedload in the upper-, middle-tidal flat and by uniform suspension in the lower-tidal flat due to tidal effect. Vertical sediment distribution of the core, collected near shoreline, shows coarsening-upward, poorly sorted pattern by the input of detritus resulting from coastal erosion. Considering the sedimentological features of the study area, it appears to be composed of a coastal zone changed by not only artificial reclamation, but also by natural processes such as strong wave action due to typhoons and storms during high water level and long/short-term sea level rising. As a result, tide-dominated erosional coasts show that the shore is affected by local, temporal and hydrological conditions near high tide level and that the intertidal flat is represented by a general tide-dominated sedimentary environment.

• The Korean Journal of Malacology
• /
• v.26 no.4
• /
• pp.267-273
• /
• 2010

From January to December 2007, we have investigated sediment types, environmental factors and density of clam Ruditapes philippinarum inhabited at Oeri, Naeri, Jonghyeon and Bangmiri tidal flats in Gyeonggi Bay off the west coast of Korea. Sediment types of Oeri and Jonghyeon were characterized with well sorted muddy sand. In contrast, Bangmiri tidal flat was mainly composed of poorly sorted gravelly muddy silt and Naeri was characterized with very poorly sorted muddy-sandy gravel. During the course of study, the surface water temperature, salinity, dissolved oxygen and pH ranged 3.2 to $27.0^{\circ}C$, 21.7 to 33.3 ‰, 5.6 to 12.7 mg/l and 7.36 to 8.82, respectively. The suspended solid (SS) ranged from 3.2 to 1,266.0 mg/l and chlorophyll-a level in the water column ranged $0.3-36.1{\mu}g/l$, respectively. The density of clam in the study areas was mainly determined by the harvesting activities rather than the types of substrate. Relatively higher density of clam was observed in Oeri and Bangmiri where the clam seeds were sowed by the villagers. Condition factor of clams were found to be higher in Oeri where the substrate sorting was better with higher level of chlorophyll a. It was believed that sediment types and the level of available food the two governing factors controlling the density and growth of clam in Gyeonggi Bay.