• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.176-184
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• 2012

Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.3
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• pp.409-420
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• 2021

The decrease in under keel clearance (UKC) due to the increase of draft that occurs during advancing and turning of very large vessels of different types was analyzed based on computational fluid dynamics (CFD). The trim change in the Duisburg test case (DTC) container ship was much smaller than that of the KRISO very large crude oil carrier 2 (KVLCC2). The sinkage of both ships increased gradually as the water depth became shallower. The amount of sinkage change in DTC was greater than that in KVLCC2. The maximum heel angle was much larger for DTC than for KVLCC2. Both ships showed outward heel angles up to medium-deep water. However, when the water depth became shallow, an inward heel was generated by the shallow water effect. The inward heel increased rapidly in very shallow water. For DTC, the reduction ratio was very large at very shallow water. DTC appeared to be larger than KVLCC2 in terms of the decreased UKC because of shallow water in advancing and turning. In this study, a new result was derived showing that a ship turning in a steady state due to the influence of shallow water can incline inward, which is the turning direction.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.21-26
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• 2000

For coastal service ships, the water depth is a very important parameter in the design stage of the hull form that has an influence on the restriction of the speed and draft of ships. In this study, the water depth is important for ship design. In this research, the change of total resistance, trim and sinkage due to the variation of water depth are measured by using on equipment for shallow water condition. For the basic research step about the shallow water effect, the effects on Series60($C_B=0.6$) hull form are experimented. To compare with existing experiment results, the test conditions are same with those. The water depth conditions are 10, 15, 20, 25% of LPP of the model ship, respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.179-188
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• 2012

Performance analyses of vertical breakwaters were conducted for fictitiously designed breakwaters for various water depths to analyze the influence of climate change on the structures. The performance-based design method considering sea level rise and wave height increase due to climate change was used for the performance analysis. One of the problems of the performance-based design method is the large calculation time of wave transformation. To overcome this problem, the SWAN model combined with artificial neural network was used. The significant wave height and principal wave direction at the breakwater site are quickly calculated by using a trained neural network with inputs of deepwater significant wave height and principal wave direction, and tidal level. In general, structural stability becomes low due to climate change impacts, but the trend of stability is different depending on water depth. Outside surf zone, the influence of wave height increase becomes more significant, while that of sea level rise becomes negligible, as water depth increases. Inside surf zone, the influence of both wave height increase and sea level rise diminishes as water depth decreases, but the influence of wave height increase is greater than that of sea level rise. Reinforcement and maintenance policies for vertical breakwaters should be established with consideration of these results.

• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.405-420
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• 2007

This study is intended to analyze and evaluate the effects of Seomjingang Dam and Soyanggang Dam Catchment on water circulation in order to examine water balance change of watershed by climate change. Obviously, air temperature and precipitation showed a gradually increasing trend for the past 30 years; evapotranspiration vary in areas and increasing annual average air temperature is not always proportional to increasing evapotranspiration. Based on Penman-FAO24, climatic water balance methods and measured values are shown to be significantly related with each other and to be available in Korea. It is certainly recognized that increasing annual rainfall volume leads to increasing annual runoff depth; for fluctuation in annual runoff rates, there are some difference in changes in measured values and calculated values. It is presumably early to determine that climate changes has a significant effect on runoff characteristic at dam catchment. It is widely known that climate changes are expected to cause many difficulties in water resources and disaster management. To take appropriate measures, deeper understanding is necessary for climatological conditions and variability of hydrology and to have more careful prospection and to accumulate highly reliable knowledge would be prerequisites for hydrometric network.

• Ecology and Resilient Infrastructure
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• v.5 no.4
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• pp.210-218
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• 2018

In this study, a real-scale stairway model was constructed to analyze the evacuation safety of human life due to the change of flooded stair flow. In the experiment, the water depth and flow velocity at each stage of the stairs were measured and the specific force per unit width was calculated. Using the calculated the specific force per unit width, the evacuation safety of each steps of stairs according to the change of the flooded stair flow was presented. Finally, the depth of water measured by the experiment and the evacuation safety graph of "Ishigaki" by the specific force per unit width were combined to analyze the evacuation safety by depth. As a result, it has been found that evacuation of adult man is difficult without help at the flow depth of 0.20 m or more. And it has been found that evacuation of adult women and elderly men are difficult without help at the flow depth of 0.15 m or more. Finally, it has been found that evacuation of elderly women is difficult without help at depth of 0.13 m or more.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.1
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• pp.2853-2877
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• 1973

Models of cross-sections and channels were made in order to measure seepage losses. Cross-sections were made of sand, sandy clay loam and loam, their thicknesses being 30cm and 40cm, respectively. Flow depths kept in the cross-sections were 4cm, 6cm, 8cm and 10cm. Straight and curved channel models were provided so as to measure seepage losses, when constant water depths maintained at the heads of the channels were 7.3cm and 5.7cm, respectively. The results obtained in this experiment are presented as follows: 1) A cumulative seepage loss per unit length at a point in the channel varies in accordance with time and flow depth. The general equation of cumulative seepage loss may be as follows(Ref. to Table V.25): $$q_{cum}=\int_{o}^aq(a)dt+\int_a^bq(b)dt+\int_b^tq(c)dt$$ 2) In case that the variation of water depth through the channel is slight, the total seepage loss may be computed by applying the following general equation: $$\={q}_{cum}{\cdot}x=\int_o^tq_{cum}\frac{{\partial}x}{{\partial}t}dt$$ 3) Because seepage loss varies considerably according to water depth in case that the variation of flow depth through the channel is great, seepage loss should be computed by taking account of the change of flow depth. 4) The relation between time and traveling distance of water flow may be presented as the following general equation(Ref. to Table V.29): $$x=pt^r$$ 5) The ratios of the seepage losses of the straight channel to the curved channel are 1:1.03 for a flow depth of 7.3cm and 1:1.068 for that of 5.7cm. 6) The ratios of the seepage losses occurring through the bottom to those through the inclined plane in the channel cross-section are 1:2.24 for a water depth of 8cm and 1:2.47 for a depth of 10cm in case that soil-layer is 30cm in thickness. Similarly, those ratios are 1:2.62 and 1:2.93 in case of a soil-layer thickness of 40cm(Ref. to Table V.5).

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.2
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• pp.235-247
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• 2006

Aerosol indirect radiative forcing of climate change is considered the most uncertain forcing of climate change over the industrial period, despite numerous studies demonstrating such modification of cloud properties and several studies quantifying resulting changes in shortwave radiative fluxes. Detection of this effect is made difficult by the large inherent variability in cloud liquid water path (LWP): the dominant controlling influence of LWP on optical depth and albedo masks any aerosol influences. Here we have used ground-based remote sensing of cloud optical depth (${\tau}_c$) by narrowband radiometry and LWP by microwave radiometry to determine the dependence of optical depth on LWP, thereby permitting examination of aerosol influence. The method is limited to complete overcast conditions with liquid-phase single layer clouds, as determined mainly by millimeter wave cloud radar. The results demonstrate substantial (factor of 2) day-to-day variation in cloud drop effective radius at the ARM Southern Great Plains site that is weakly associated with variation in aerosol loading as characterized by light-scattering coefficient at the surface. The substantial scatter suggests the importance of meteorological influences on cloud drop size as well, which should be analyzed in the further intensive studies. Meanwhile, it is notable that the decrease in cloud drop effective radius results in marked increase in cloud albedo.

• Water Engineering Research
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• v.5 no.3
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• pp.111-121
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• 2004

For the long-term strategic water resources planning, forecasting the future streamflow change is important to meet the demand of a growing society. The streamflow variation to the decade-long precipitation was investigated for the two major stage gauging stations in Korea. Precipitation and runoff characteristics have been analyzed at Yongwol stream stage in the Han River as well as Sutong stream stage in the Kum River for the future water resources management strategies. Monte Carlo method has been applied to estimate the future precipitation and runoff. Based on the trend line of 10-year moving average of runoff depth for the historical runoff records, the relation between runoff and the time variation was examined in more detail using regression analysis. This study showed that the surface flows have been significantly decreased while precipitation has been stable in these basins. Decreasing in runoff reflects the regional watershed characteristics such as forest cover changes. The findings of this study could contribute to the planning and development for the efficient water resources utilization.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.741-746
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• 2003

The foundation of Noksan area is composed of consolidified sediments including clay mineral, quartz, plagioclase and calcite. The mineral compositions vary dependent on the depth. That is, at the depth of 0-15 meters quartz and plagioclase are more abundant than clay mineral, at the depth of 17-39 meters clay minerals and calcite are more than quartz and plagioclase, at the depth deeper than 40 meters, the amounts of quartz and plagioclase increase slightly and that of clay minerals decrease. Clay minerals of the clayey sediments include illite, smectite, kaolinite and chlorite. At the depth 17-39 meters smectite is abundant and kaolinite is little relatively The pH of suspension is various between 3-9 and decrease to 3-5 at the depth deeper than 40 meters. The result of soil test of clay sediments, water content shows that liquid limit, plastic limit, particle size, unconfined compressive strength varies depending on the depth. The variation of mineralogical, geochemical, engineering properties of soil with the depth are probably due the differing sediments of different sedimentary environment. That is, these variations are considered to be correlated with the sedimentary environment change resulting from the change from continental environment to ocean environment due to the transgression of the interglacial period after the regression the latest glacial period.