Outline of the Ocean Nutrient Enhancer 'TAKUMI'

Ouchi, Kazuyuki The Korean Association of Ocean Science and Techno 2005 Journal of Ocean Science and Technology Vol.2 No.1

The five years project of increasing a primary production and making a new fishing ground by upwelling Deep Ocean Water (DOW) which is very rich in nutrient salt such as Nitrogen, Phosphorus, etc. was commenced in the year of 2000, sponsored by the Fisheries Agency of Japanese Government and Marino-Forum 21. In the open ocean, so far, there are no successful means to upwell DOW artificially and to make a fishing ground. Therefore, the focus of the project is a creation and proposition of the concept of Ocean Nutrient Enhancer (ONE) to contribute for increasing primary productions and fish productions, furthermore, conducting the experiment in actual sea to" confirm the effect of the ONE. The requisite technologies for the ONE such as making an artificial density current, a spar type floating structure, a hang off steel riser pipe, a set-up way of upending the riser pipe, etc. was discussed and integrated to create proto-type of ONE, whose main specifications are the DOW upwelling depth and capacity of 200 m and 100,000 $m^3/day$, the displacement of about 1,700tons, and Diesel engine of 100 KW. The ONE was set-up with the single point mooring system at the centre of rotational flow in Sagami Bay in the depth of about 1,000 m, and came into the operation in June 2003. In this paper, the outline of the prototype of ONE which was named "TAKUMI" is introduced.

Historical Trend of Butyltin Contamination in Sediment Cores from the Coastal Environments of Korea

Shim, Won-Joon,Yim, Un-Hyuk,Kim, Nam-Sook,Hong, Sang-Hee,Oh, Jae-Ryoung The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.1

In the present study, butyltin compounds in sediment cores were quantitatively determined to study vertical distribution of these compounds along the coast of Korea. Butyltins in sediment core were analyzed to investigate the trend of past organotin contamination in Korea and to estimate the half-life of TBT in sediments. Butyltin compounds were detected from the entire sediment core samples at 14 stations. TBT, and its degradation products, dibutyltin (DBT) and monobutyltin (MBT), concentrations ranged 〈1-46100, 〈1-4320 and 〈2-2460 ng Sn/g on a dry weigt basis, respectively. The highest butyltin concentrations were found in front of the repairing shipyard in Ulsan Bay at which total butyltin concentration reached up to 51620 ng Sn/g. Each butyltin compound showed significant correlation among tri-, di- and mono-substituted compounds. Sedimentation rates were estimated based on $^{210}$ Pb activity profiles. The half-lives of TBT in eight undisturbed sediment cores were calculated from the estimated sediment age and TBT concentration profiles. The half-lives for TBT ranged from 1.8 to 9.9 years and the mean value was 4.9 year. Relatively longer half-lives were obtained from cores Ulsan Bay (9.9 yr), Kamak Bay (8.3 yr) and Dangdong Bay (6.3 yr). The half-lives of the other cores were less than 5 yr. Butyltin concentrations were high enough to affect marine organisms near harbor and shipyard, and vertical distribution of butyltin compounds in sediment showed active use of them in Korean peninsula for the past decades. The half-lives of TBT in a year scale provide a concern on persistence of this compound in marine sediment even after world-wide total ban on use of TBT.

Analysis of Three-Dimensional Radiation Problem by B-Spline Higher Order Panel Method

Kim, Gun-Do,Lee, Chang-Sup,Hong, Do-Chun The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.1

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvintype Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semi spherical body floating on the free surface for six-degrees of freedom motion. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.

Non-Hydrostatic Model of Near Shore Flow Calculation

Yoon, Bum-Sang,Park, Chul-Woo The Korean Association of Ocean Science and Techno 2006 Journal of Ocean Science and Technology Vol.3 No.1

In this paper, the fractional step approach is applied to calculation of flow in near shore area with complicated boundary shape in order to consider non-hydrostatic pressure induced by geometrical irregularities at the boundaries. At a time instant, intermediate solutions for flow velocities and free surface are obtained through the hydrostatic multi-layer calculation in the first step, and non-hydrostatic pressure field is predicted using the intermediate solutions in the second step. In the third step, final solutions are calculated considering not only hydrostatic pressure but also non-hydrostatic pressure. Present calculation algorithm with fully explicit finite difference scheme in ${\sigma}$a-coordinate is successfully applied to the near shore flow calculation. Hydrostatic model is thought practically good tool enough to predict general ocean circulation problems. However, effects of non-hydrostatic pressure on flow field and free surface movements are to be emphasized, not negligible, in the vicinity of irregularities both of continental and bottom boundaries. Present method can be applied to the mesoscale free surface flows with complex bottom topography where MAC-like 3-d hydrodynamic calculations are quite ineffective and uneconomic.

Design Sensitivity Analysis and Topology Optimization of Displacement-Loaded Structures

Jung, Hyun-Seung,Cho, Seonho The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.2

A continuum-based design sensitivity analysis (DSA) method for the systems with non-homogeneous boundary condition is developed for the topology optimization of displacement-loaded structures. The non-homogeneous Dirichlet problem is transformed into a homogeneous one. An adjoint variable method (AVM) is selected to efficiently compute the design sensitivity of the problems. For the topology optimization, we employ the density method using a bulk material density to distribute the material. The design sensitivity expressions for the performance measures such as displacement and rigidity functional are derived for the topology optimization. It is shown that the solution space requires just homogeneous boundary conditions in adjoint systems whereas the original problem has non-homogeneous one. Numerical examples for the developed method are performed by comparing the analytical sensitivities with the finite differencing, which show excellent agreements. The topology optimization result for the displacement-loaded systems is shown to be equivalent to that for the force-loaded systems.

A Slamming Experiment Using Air Pressure Cylinder

Kwon, Sun-Hong,Jung, Doo-Jin,Song, Ki-Jong,Jung, Byoung-Hoon The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.2

This paper proposes an alternative experimental technique for slamming experiments. The main idea of the proposed experiment is to replace the free-fall of the specimen, by accelerating the specimen using an air pressure cylinder at a very short distance from the water surface. The travel distance of the specimen was less than 10cm. The experiments have high repeatability. The maximum pressure peak was almost the same when the results from the free-fall experiment were compared with those from the air pressure cylinder experiment. The proposed experimental technique on slamming, by using an air pressure cylinder, was shown to be quite promising.

Position Control for the Buffer of a Deep-sea Mining System

Kim, Ki-Hun,Choi, Hang-S.,Hong, Sup The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.1

This paper describes a position-control algorithm for the buffer of a deep-sea mining system. The buffer is connected to a surface vessel by means of a long slender pipe on its top and to a collector on sea floor through a flexible hose at the bottom. A mathematical modeling is established for designing the controller for thrusters of the buffer, in which the dynamic response of the long pipe is taken into account. In this paper, the dynamic response is estimated by the mode superposition method and the fluid loading acting on the pipe is computed by using Morisons formula. For simplicity, the reaction from the flexible hose is not included and only the lateral motion is considered. The control algorithm is based on the PID control method. In order to guide the buffer to react only to the low-frequency motion of the surface vessel, the FIR digital filter is introduced. It can be shown numerically that the high-frequency component of ships motion can be successfully filtered out by using the FIR low pass filter.

Evaluation of Crest Freeboard of Rubble-Mound Breakwaters by Reliability Analysis of Wave Run-up

Lee, Cheol-Eung The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.2

A reliability analysis model for studying the influence of joint distribution of wave heights and periods on wave run-up and considering the fluctuation of water level is presented in this paper. Based on the definition of failure mode related to wave run-up, a reliability function may be formulated straightforwardly. In particular, the reliability analysis model can be directly taken into account the statistical properties and distributions of wave periods by treating the wave period in the reliability function to be a random variable. Also, the behaviour of wave height distribution conditioned to mean wave periods can be taken into account properly. It is found from the sensitivity analysis that the probabilities of failure of wave run-up is more dependent on the wave height than other variables such as seaside slope of structure. Additionally, it may be concluded that the effect of spectral bandwidth parameter on reliability index may be negligible. However, the effect of wave periods on the probability of failure of wave run-up may be indirectly appeared through the distribution of wave heights conditioned to the mean wave period. Finally, we can estimate the probabilities of failure with respect to the crest freeboard of rubble-mound breakwater, by which the optimal design of crest freeboard of rubble-mound breakwaters may be possible.

Regional Co-Operation on Marine Pollution Preparedness and Response in the Northwest Pacific-with a Special Reference to NOWPAP Regional Oil Spill Contingency Plan

Kang, Seong-Gil,Oh, Jeong-Hwan,Kang, Chang-Gu The Korean Association of Ocean Science and Techno 2006 Journal of Ocean Science and Technology Vol.3 No.1

In today's world, oil spills are a major environmental problem. In total, millions of tones of oil have been spilled into the world's ocean, resulting in enormous impacts on fisheries, wildlife and their habitats, coastal industries and tourism, and even on political and social aspects, etc. The sea area of the far-eastern Asian countries-that is, Northwest Pacific region, was regarded as the area facing the highest risk of oil spill in the world. In fact, 19 major oil spills (greater than 1,000 tons), 124 intermediate spills ($50{\sim}1,000$ tons), and innumerable small spills (less than 50 tons) have been occurred in the area from 1990-2004. Based upon the perception of high risk of oil spill, the four countries bordering the Northwest Pacific (China, Japan, R. Korea and Russia) have developed effective measures for regional cooperation in marine pollution preparedness and response within the framework of the Northwest Pacific Action Plan (NOWPAP), agreed in 1994 by the governments. They have especially developed the NOWPAP Regional Oil Spill Contingency Plan and its Memorandum of Understanding, which will be a firm foundation in our strong partnership among NOWPAP Members in the relevant field. The present paper introduces current activities of MERRAC as a new regional initiative on marine pollution preparedness and response in the NOWPAP region, together with analysis of oil spill risk in the region and regional preparedness and response system to oil spill, with a special reference to NOWPAP Regional Oil Spill Contingency Plan.

On the Reverse of Streamwise Velocity Deficit in Formation of Boundary-layer Streaks

Suh, Sung-Bu,Boiko, Andrey V.,Chun, H. H. The Korean Association of Ocean Science and Techno 2005 Journal of Ocean Science and Technology Vol.2 No.1

The phenomenon of transformation of streamwise velocity deficit to excess in a near-wall wake behind a flat-plate roughness observed previously in numerous experiments is analyzed qualitatively by means of theories of optimal disturbances based on linearized Navier-Stokes and linearized boundary layer equations. It is shown that the reverse of the velocity deficit can accompany the excitation of a streak and that the formation of two maxima in the disturbance stream wise velocity profiles also observed in the experiments can be a side effect of the streak nonoptimality. An experimental approach aimed to provide quantitative data for comparison with a numerical solution of corresponding initial value problem is suggested.