• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.301-308
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• 2010

Quest for reliability of hydraulic runners is a concern for all mature electricity producers. The fatigue damage caused by dynamics loads is frequently the root cause of runner failure. This paper presents the damage tolerance approach based on fracture mechanics as the method chosen by Alstom and Hydro-Qu$\acute{e}$bec to predict effects of damage on runner lifetime and consequently to be use as a design method. This is sustained by a research on fracture mechanics properties of runner materials and by recommendations on the strategy to define a safety margin for design. The acquired knowledge permits to identify potential improvement of the runner lifetime without significant cost increase, like being more specific on some chemical composition or heat treatment.

• Nuclear Engineering and Technology
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• v.37 no.6
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• pp.525-536
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• 2005

The interfacial area transport equation dynamically models the changes in interfacial structures along the flow field by mechanistically modeling the creation and destruction of dispersed phase. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport mechanism for various sizes of bubbles, the transport equation is formulated for two characteristic groups of bubbles. The group 1 equation describes the transport of small-dispersed bubbles, whereas the group 2 equation describes the transport of large cap, slug or chum-turbulent bubbles. To evaluate the feasibility and reliability of interfacial area transport equation available at present, it is benchmarked by an extensive database established in various two-phase flow configurations spanning from bubbly to chum-turbulent flow regimes. The geometrical effect in interfacial area transport is examined by the data acquired in vertical fir-water two-phase flow through round pipes of various sizes and a confined flow duct, and by those acquired In vertical co-current downward air-water two-phase flow through round pipes of two different sizes.

• International Journal of Fluid Machinery and Systems
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• v.5 no.4
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• pp.174-179
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• 2012

A numerical study to investigate the effect of intake vortex occurrence on the performance of an axial hydraulic turbine for generating tidal power energy in Sihwa-lake tidal power plant, Korea, is performed. Numerical analysis of the flow through an sxial hydraulic turbine is carried out by solving three-dimensional Reynolds-averaged Navier-Stokes dquations with the shear stress transport turbulence model. In the real turbine operation, the vortex flows are occurred in both the side corners around the intake of an axial hydraulic turbine due to the interaction between the inflow angle of water and intake structure. To analyze these vortex phenomena and to evaluate their impacts on the turbine performance, the internal flow fields of the axial hydraulic turbines with the different inflow angles are compared with their performances. As the results of numerical analysis, the vortex flows do not directly affect the turbine performance.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1121-1134
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• 2014

The distributed watershed model of rainfall-runoff-soil erosion-sedimen transport was constructed for the Naesung Stream Watershed with high potentiality and risk of sediments produced by soil erosion. The sensitivity analyses of roughness coefficient and hydraulic conductivity which affected the modeling results of runoff and sediment concentration were performed in this study. As a result, the change of the roughness coefficient for the forest area from 0.4 to 0.45 did not affect the change in runoff and stream discharge and the average value and range of sediment concentration were also insignificantly increased with few difference. As a result of the sensitivity analysis of the hydraulic conductivity, the total amount of runoff and maximum runoff were gradually increased as the hydraulic conductivity was reduced. In the case of sediment concentration modeling, the average and the range of sediment concentration for all stations were increased as the hydraulic conductivity was decreased. For the Hyangseok Station, in case of the hydraulic conductivity reduced by 50%, the simulation result of sediment concentration was most similar to the estimated value by the sediment rating curve.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.3
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• pp.154-161
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• 2017

The purpose of this study was to investigate the change of length, opening width, and number of openings effecting on topography change around artificial reefs under erosive wave condition. Hydraulic model test was conducted to see sediment transport around the structures and the relation among the installation condition of the artificial reefs, generated velocity, wave deformation, and topographic change was reviewed. Experimental results show that the sediment transport rate was reduced; however, the scour around the structures was increased under the condition of having a single opening compared to the structures having a plurality of openings which shows inversely proportional to the size of Lr/W.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.4
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• pp.455-468
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• 2022

Colloid Formation and Migration (CFM) project is being carried out within the Grimsel Test Site (GTS) Phase Ⅵ. Since 2008, the Korea Atomic Energy Research Institute (KAERI) has joined CFM to investigate the behavior of colloid-facilitated radionuclide transport in a generic Underground Research Laboratory (URL). The CFM project includes a long-term in-situ test (LIT) and an in-rock bentonite erosion test (i-BET) to assess the in-situ colloid-facilitated radionuclide transport through the bentonite erosion in the natural flow field. In the LIT experiment, radionuclide-containing compacted bentonite was equipped with a triple-packer system and then positioned at the borehole in the shear zone. It was observed that colloid transport was limited owing to the low swelling pressure and low hydraulic conductivity. Therefore, a postmortem analysis is being conducted to estimate the partial migration and diffusion of radionuclides. The i-BET experiment, that focuses more on bentonite erosion, was newly designed to assess colloid formation in another flow field. The i-BET experiment started with the placement of compacted bentonite rings in the double-packer system, and the hydraulic parameters and bentonite erosion have been monitored since December 2018.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.576-578
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• 2005

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.spc
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• pp.8-13
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• 2009

Mathematical models have become increasingly popular in both research and management problems involving flow and transport processes in the subsurface. Rosetta is a program to estimate unsaturated hydraulic properties from surrogate soil data such as soil texture data and bulk density. Models of this type are called pedotransfer functions (PTFs) as an alternative measurements since they translate basic soil data into hydraulic properties. These functions may be either measured directly or estimated indirectly through prediction from more easily measured data based using quasi-empirical models.

• Journal of the Korean Institute of Navigation
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• v.13 no.1
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• pp.77-106
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• 1989

Two numerical models of the shoreline change and sediment transport rates, explicit and implicit, are simulated with shore structures such as breakwaters, a jetty, groins and a seawall. The applied study area is songdo Beach, Youngil bay, Korea since it has all the shore structures mentinoed above. The two models investigate the beach line changes and sedimen transport rates for the beach before design of three groins with and without an offshore breakwater. In order to estimate the shoreline changes after three groins were built, the beach response inside the three groin compartiments and the offshore barrier are also investigated. The simulation based on the initial shoreline conditions surveyed by the Hydrographic office, Koreai 1979 and 1984. The breaking wave characteristics are introduced into the models by calculation from the empirical equations and modification from the numerical and hydraulic model test results developed for waves behind an offshore breakwater. The numerical simulation describes well the tendencies of the sand transport and shoreline changes affected by wave diffraction behind a detached breakwater and by interruption of sand transport at three groins.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.305-310
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• 1998

This research conducted concerning measures for the influence reduction to an investigation in the structure of offshore breakwater maintenance, an evaluation, a reexamination of the forecast, and a peripheral sediment transport environment. Furthermore, it aimed at the establishment of the beach transformation forecast method based on a hydraulic model study and a numeric simulation. A good result was obtained from a hydraulic model experiment and a numeric simulation as part of the basic research. And a qualitative evaluation of the flow field around the structure became possible since a numeric simulation examined flow field characteristics.