• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.49-59
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• 1999

In order to understand the present situation of bridge scouring and to provide the fundamental information for bridge design, in-situ measured data is analyzed for bridge scours at small and medium streams in the heartland of Korea. The physical parameters affecting the bridge scouring such as flow depth, velocity, pier length and width, scouring depth, and the angle between flow and pier are extensively surveyed and measured. According to the locality and the pier type data are classified to analyze. With these data, some important factors for the scour depth such as flow depth, angle and Froude number are investigated and applied to existing formulas proposed by many researchers. In addition, the computational results are compared with the measured and some of the applicable formulas in this region are recommended.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.930-937
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• 2011

The characteristics of mean velocity and turbulence have been analyzed in the circular open channel flow using PIV measurement data for a wide range of water depth. The measured data are fitted to a velocity distribution function over the whole depth of the open channel. Reynolds shear stress and mean velocity in wall unit are compared with the analytic models for fully-developed turbulent boundary layer. Both the mean velocity and Reynolds shear stress have different distributions from the two-dimensional boundary layer flow when the water depth increases over 50% since the influence of the side wall penetrates more deeply into the free surface. The cross-stream Reynolds normal stress also has considerably different distribution in view of its peak value and decreasing rate in the outer region whether the water depth is higher than 50% or not.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.59-68
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• 2006

Flow separation of recirculation zone by increasing of flow and change of its direction at confluence results in backwater due to conveyance reduction. The hydraulic characteristics of flow separation are analysed by experimental results of flow ratios of tributary and main streams and approaching angles. The boundary of flow separation by dimensionless length and width is defined by the streamline of zero and this definition agrees well to the existing investigation. Because flow separation doesn't appear in small flow ratio and approaching angle of $30^{\circ}$, the equation of flow separation with flow ratio and approaching angle is provided. In flow separation consideration and comparing with previous results, the existing equations of dimensionless length and width ratios by function of approaching angle, flow ratio, and downstream Froude number are modified and also contraction coefficient and shape factor are analysed. Dimensionless length and width ratios are proportional to the flow ratio and approaching angle. In analysis of water surface profiles, the backwater effects are proportional to the flow ratio and approaching angle and the magnitude at outside wall is greater than that of inside wall of main stream. The length, $X_l$ from the beginning of confluence to downstream of uniform flow, where the depth is equal to uniform depth, is characterized by width of stream, flow ratio, approaching angle, and contraction coefficient. The ratios between maximum water depth by backwater and minimum depth at separation are analysed.

• Journal of the Korea Furniture Society
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• v.18 no.2
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• pp.161-165
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• 2007

An experiment was conducted to observe the safranine flow depth in longitudinal direction of Populus tomentiglandulosa. Longitudinal flow of safranine was considered from bottom to top end of the tree. Vessel and wood fiber were considered for the measurement of safranine flow depth. It was found that sapwood conducted safranine 12.25% higher in longitudinal direction compared with heartwood. Vessel was found the main avenue for safranine flow. Vessel conducted safranine 41.94% higher than that of wood fiber. Safranine penetrated through vessel and fiber forming a curved meniscus.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.573-576
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• 2006

The objective of the study is to investigate the depth of penetration of concrete water forced in under pressure. For this purpose, the experiments for the depth of penetration by selecting the factors and levels such as water pressure, pressure time were executed. The flow of water of concrete examined theoretically and experimentally. As a result, It is found that in the case of low water pressure approximately 0.15Mpa or less, the flow is Darcy seepage flow, the same as flow in an ordinary sand stratum, whereas in the case of high water pressure, the flow is diffused seepage flow accompanied by internal deformation of concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1897-1903
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• 2011

This paper discusses a 2D/3D conversion of images using technologies like object extraction and depth-map creation. The general procedure for converting 2D images into a 3D image is extracting objects from 2D image, recognizing the distance of each points, generating the 3D image and correcting the image to generate with less noise. This paper proposes modified new methods creating a depth-map from 2D image and recognizing the distance of objects in it. Depth-map information which determines the distance of objects is the key data creating a 3D image from 2D images. To get more accurate depth-map data, noise filtering is applied to the optical flow. With the proposed method, better depth-map information is calculated and better 3D image is constructed.

• Journal of Environmental Science International
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• v.20 no.11
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• pp.1457-1464
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• 2011

In this study, the method of estimating hydrologic information (water depth, submerged period etc.) on the proper selection of construction point and scale as well as vegetation type suggested for the design of natural riparian rehabilitation structure. Long-term comprehensive watershed model SWAT-K(Korea) was applied to this purpose. Flow duration analysis was conducted to analyze the hydrologic characteristics of Pyungchang watershed at which the 'bangtul' construction method was tested. For this purpose 20 years (1989-2008) rainfall runoff analysis was carried out. Based on the simulated daily streamflow data, flow duration curve was made to analyze the flow characteristics, and the water depth hydrograph was made to analyze the water depth distribution at the cross section. Finally, the information for the selection of proper vegetation according to the submerged period is suggested.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.93-101
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• 2015

This paper provides numerical results of the simulation for the flow around the hull and the propeller of KCS model ship advancing in shallow water conditions. A finite volume method is used to solve the unsteady Reynolds averaged Navier-Stokes(RANS) equations, where the wave-making problem is solved by using a volume-of-fluid(VOF) method. The wave formed near the hull surface in shallow water conditions shows a deep trough dominant pattern that causes the loss of buoyancy followed by hull squat. The flow past the hull increases as the depth of water decreases. However, the axial flow velocity around the stern shows a reduction in magnitude by the effect of shallow water accompanied by the hull-propeller interaction. As a results, the thrust and torque coefficient increase about 8.3% and 6.2%, respectively for a depth of h/T=3.0 corresponding to a depth Froude number of $F_h=0.693$. The resistance coefficient increases about 11.6% at this Froude number condition.

• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.529-538
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• 1998

The flow configurations at open channel junctions are analyzed by 2-D depth averaged mathematical model. The governing factors of the flow at the junction are found to be discharge ratio between tributary flow and the post confluence combined flow, and confluence angle. Analyzed by these two factors are flow patterns and flow depth variation at the confluence, discharge ratio above which the flow upstresm from the junction is affected by the tributary flow and the geometries of a recirculation region. Further, the flow contraction in the downstream region and the deflection of the tributary flow in the main channel were investigated. The numerical results are compared with the existing experimental data fairly well.

• Water for future
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• v.27 no.2
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• pp.111-120
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• 1994

In this experimental research, the maximum scour depth at pier was studied. The model of the pier of San Gye bridge in the Bocheong stream was set for experimental pier scour studies. Several model verification processes were conducted through the roughness comparisons between model and prototype, pursuring scour depth variations with time depending upon channel bed variation, the comparison of the ratio between falling velocities and shear velocities in the model and prototype, and the comparison of pier scour between experimental data and field measuring data. The experiments were conducted in the free flow conditions and pressure flow conditions. The maximum scour depth at piers in the pressure flow conditions is twice as much as compared to the free flow conditions. Also, the maximum scour depth variations are indicated in the figures based on the Froude numbers, opening ratios, water depths and approaching angles in the free surface flow conditions.