• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.471-482
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• 2022

This study aims to investigate the characteristics of wave generation in a deep ocean engineering basin and to develop a meta-model of the transfer function of the wavemaker that reflects the geometric characteristics of the deep ocean engineering basin. To this end, the two-dimensional frequency domain boundary element method was applied to achieve an efficient analysis that reflects the geometric characteristics of the deep ocean engineering basin. The developed numerical method was validated through comparison with the analytical solution. Numerical analyses were conducted for the boundary value problem of the wavemaker according to various periods and the positions of the movable bottom. The numerical results were used to investigate the effect of the geometric characteristics of the deep ocean engineering basin on the transfer function of the wavemaker, and the effect of depth on wave generation was checked by changing the position of the movable bottom. To efficiently utilize the various results of the boundary element method, a meta-model, an approximate model of the transfer function of the wave maker, was developed using a thin plate spline interpolation model. The validity of the developed meta-model was confirmed through a comparison of the results of the model tests.

• Korean Journal of Agricultural Science
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• v.8 no.2
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• pp.195-202
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• 1981

The return of water to the atmosphere from water, soil and vegetation surface is one of the most important aspects of hydrological cycle, and the seasonal trend of variation of river basin evaporation is also meaningful in the longterm runoff analysis for the irrigation and water resources planning. This paper has been prepared to show some imformation to estimate the monthly river basin evaporation from pan evaporation, potential evaporation, regional evaporation and temperature through the comparison with river basin evaporation derived from water budget method. The analysis has been carried out with the observation data of Yongdam station in the Geum river basin for five year. The results are summarized as follows and these would be applied to the estimation of river basin evaporation and longterm runoff in ungaged station. 1. The ratio of pan evaporation to river basin evaporation ($E_w/E_{pan}$) shows the most- significant relation at the viewpoint of seasonal trend of variation. River basin evaporation could be estimated from the pan evaporation through either Fig. 9 or Table-7. 2. Local coefficients of cloudness effect and wind function has been determined to apply the Penman's mass and energy transfer equation to the estimation of river basin evaporation. $R_c=R_a(0.13+0.52n/D)$ $E=0.35(e_s-e)(1.8+1.0U)$ 3. It seems that Regional evaporation concept $E_R=(1-a)R_C-E_p$ has kept functional errors due to the inapplicable assumptions. But it is desirable that this kind of function which contains the results of complex physical, chemical and biological processes of river basin evaporation should be developed. 4. Monthly river basin evaporation could be approximately estimated from the monthly average temperature through either the equation of $E_w=1.44{\times}1.08^T$ or Fig. 12 in the stations with poor climatological observation data.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.397-410
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• 2002

In order to quantitatively identify historical drought conditions and to evaluate their variability, drought indices commonly used. The calculation method for the drought index based on the principal hydrological factors, such as precipitation and reservoir storage, can estimate the duration and intensity of a drought. In this study the Palmer-type formula for drought index is derived for the Nakdong River basin by analyzing the monthly rainfall and meteorological data at 21 stations. The Palmer Drought Severity Index(PDSI) is used for dry land sectors to evaluate the meteorological anomaly in terms of an index which permits time and space comparisons of drought severity. The Surface Water Supply Index(SWSI) is devised for the use in conjunction with the Palmer index to provide an objective indicator of water supply conditions in Nakdong River basin. The SWSI was designed to quantify surface water supply capability of a watershed which depends on river and reservoir water The Standardized Precipitation Index(SPI) is evaluated for various time periods of 1 to 12 months in Nakdong River basin. For the purpose of comparison between drought indices correlation coefficient was calculated between indices and appropriate SPI time period was selected as 10 months for Nakdong River basin. A comparative study is made to evaluate the relative severity of the significant droughts occurred in Nakdong River basin since 1976. It turned out that $'94{\sim}'97$ drought was the worst drought in it's severity. It is found that drought indices are very useful tools in quantitatively evaluating the severity of a drought over a river basin.

• Journal of Korea Water Resources Association
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• v.41 no.5
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• pp.491-501
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• 2008

In order to describe runoff characteristics of urban drainage area, outflow from subbasins divided by considering topography and flow path, is analyzed through stormwater system. In doing so, concentration time and time-area curve change significantly according to basin shape, and runoff characteristics are changed greatly by these attributes. Therefore, in this development study of FFC2Q model by MLTM, we aim to improve the accuracy in analyzing runoff by adding a module that considers basin shape, giving it an advantage over popular urban hydrology models, such as SWMM and ILLUDAS, that can not account for geometric shape of a basin due to their assumptions of unit subbasin as having a simple rectangular form. For subbasin shapes, symmetry types (rectangular, ellipse, lozenge), divergent types (triangle, trapezoid), and convergent types (inverted triangle, inverted trapezoid) have been analyzed in application of time-area curve for surface runoff analysis. As a result, we found that runoff characteristic can be quite different depending on basin shape. For example, when Gunja basin was represented by lozenge shape, the best results for peak flow discharge and overall shape of runoff hydrograph were achieved in comparison to observed data. Additionally, in case of considering subbasin shape, the number of division of drainage basin did not affect peak flow magnitude and gave stable results close to observed data. However, in case of representing the shape of subbasins by traditional rectangular approximation, the division number had sensitive effects on the analysis results.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.109-117
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• 2010

This study quantified the storm direction for a river basin by applying the von Mises distribution, also determined the representative storm direction. Additionally, the whole procedure was repeated for several storm types such as frontal, typhoon and convective storms for their comparison. From the results derived by analyzing a total of 101 storm events for the Naesung river basin, the von Mises distribution was found to explain the directional characteristics of storms. The representative moving directions derived for three different storm types were significantly different each other, which is coincident with the climate of Korea. The results derived in this study could be helpful to estimate more quantitatively the difference in the runoff response with respect to the moving direction of a storm.

• Ocean Systems Engineering
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• v.8 no.4
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• pp.427-439
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• 2018

Floating Production Storage and Offloading (FPSO) units have the advantages of their ability to provide storage and offloading capabilities which are not available in other types of floating production systems. In addition, FPSOs also provide a large deck area and substantial topsides payload capacity. They are in use in a variety of water depths and environments around the world. It is a good solution for offshore oil and gas development in fields where there is lack of an export pipeline system to shore. However due to their inherently high motions in waves, they are limited in the types of risers they can host. The Low Motion FPSO (LM-FPSO) is a novel design that is developed to maintain the advantages of the conventional FPSOs while offering significantly lower motion responses. The LM-FPSO design generally consists of a box-shape hull with large storage capacity, a free-hanging solid ballast tank (SBT) located certain distance below the hull keel, a few groups of tendons arranged to connect the SBT to the hull, a mooring system for station keeping, and a riser system. The addition of SBT to the floater results in a significant increase in heave, roll and pitch natural periods, mainly through the mass and added mass of the SBT, which significantly reduces motions in the wave frequency range. Model tests were performed at the Korea Research Institute of Ships & Ocean Engineering (KRISO) in the fall of 2016. An analytical model of the basin model (MOM) was created in Orcaflex and calibrated against the basin-model. Good agreement is achieved between global performance results from MOM's predictions and basin model measurements. The model test measurements have further verified the superior motion response of LM-FPSO. In this paper, numerical results are presented to demonstrate the comparison and correlation of the MOM results with model test measurements. The verification of the superior motion response through model test measurements is also presented in this paper.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.6
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• pp.497-506
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• 2015

Gravity variations due to the 2011 Tohoku (M9.0) earthquake, which occurred at the plate boundaries near the northeastern coast of Japan, were estimated through the GRACE spherical harmonic (Stokes) coefficients derived from the CSR. About -5 μGal gravity variation by the GRACE data was found in the back-arc basin area with respect to a reference gravity model. The mean gravity variations in the back-arc basin area and the Japan Trench area were -4.4 and -3.2 μGal in order. The small negative gravity variations around the Japan Trench area can be interpreted by both crustal dilatation and the seafloor topography change in comparison with the large negative gravity variations in the back-arc basin area by co-seismic crustal dilatation of the landward plate. From the results of the gravity variations, vertical displacements generated from relatively short wavelength caused by the earthquake were estimated by use of multi-beam bathymetric measurements obtained from JAMSTEC. The maximum seafloor topography changes of about ±50 m were found at west side of the Japan Trench axis by the earthquake. The seafloor topography change by the megathrust earthquake can be considered as the results of the landslide of the seafloor throughout the landward side.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.5
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• pp.56-63
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• 2007

This study used the nearest feature model to connect forest patches within the western Geum River Basin. Due to many different forest patch sizes, 3 alternative methods were tested to determine the best way to establish an ecological network with forest patches. Alternative 1 used all forest patches to determine whether patches were large enough. Alternative 2 used forest patches over 10 ha in size. Alternative 3 used natural conservation indices to select forest patches containing better qualities in the natural conservation level. As a result 635 out of 724 patches of over 10 ha were selected for comparison. Alternative 1 showed that forest patches of less than 10 ha were outliers interrupting the establishment of the ecological network. They generated an unnecessary ecological network to link core areas to comparison features. The ecological network was improved by using forest patches greater than 10 ha in size(Alternative 2). Each comparison feature was much more hierarchically connected to core areas in Alternative 2 than in Alternative 1. Forest patches filtered by natural conservation indices were useful for obtaining the best ecological network. Alternative 3 clearly showed the connections in the ecological network between core areas and forest.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.885-894
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• 2008

The deposition of solids in combined sewer systems results in a loss of flow capacity that may restrict flow and cause a local flooding and enhanced solids deposition. In order to solve these problems and proper pipe management, estimations of solid loads on land surface in a drainage basin and solid deposition in sewer system due to rainfall are needed but these tasks are very difficult and very expensive. In this study, procedures for estimating solid loads on surface in a drainage basin were applied and analyzed in Gunja drainage basin in Korea. Also, this paper presents the development and application of estimation equation for solid deposition in sewer system due to rainfall based on the solid deposition estimated using MOUSE model. As results, the comparison between estimated and measured solid deposition is difficult due to the absent of measured data, but the estimated values using developed equations show applicability compared with the results of MOUSE model and the application of the other basin. The developed estimation equations can be used usefully for the management of combined sewer system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1341-1348
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• 1994

This is a comparative study on applications of finite analytic method (FAM) and finite difference method (FDM) to rectangular smalI basin circulation. To do such a comparison, the circulation model in small rectangular basin is established using FAM and the nurmerical solution from the FAM model is compared with that from the FDM model. As the grid size approaches Von Neumann stablity condition, the convergence time to steady state increases in Askren's model, but does not increase in finite analytic model. Especially in the FAM model, the numerical solution converges stably even in the grid size range beyond the stablity condition whereas that diverges in the FDM model. In the case of large basin Reynolds number, it is found that steady state solution is obtained in the FAM model with smaller calculating steps than those of in the FDM model.