• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.5
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• pp.528-534
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• 2003

The 2-D hydraulic experimental results for the submerged rubble-mound structure, we have been concerned with the slability/function characteristics of the structures by the effects of wave force, scour/deposition at the toe and the wave transmission ratio at the lee-side sea. So, to investigate the variation characteristics of the wave transmission ratio which depended on a geometrical structure of the submerged breakwater profiles, the critical conditions for the depth of submergence and crest width were obviously presented. In summary, the results lead us to the conclusion that the wave control capabilities of submerged breakwaters by the variation of the submergence depth is higher than about 4 times the degree at the efficiency than the that of crest width. The destruction of the covering block at the crest generated at the region which was located between the maximum and minimum damage curve, and it's maximum damage/failure station from the toe of the structure was $0.2\;L_s.$ As the wave transmission coefficient and the slope of the structure increase, the damage/failure ratio and the maximum scour depth at the toe was extended, respectively. When the maximum scour depth happened, the destruction of the covering block which was located at the toe generated at the front of the submerged rubble-mound breakwater. Finally, it was found from the results that the optimization of the structure may be obtained by the efficient decision of the submergence depth and crest width in the permissible range of the wave transmission ratio.

• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.255-263
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• 1999

The laboratory datas are for local scour depth measurement at vertical-wall abutment. These include the data to demonstrate the effects of local scour depth of abutment nose shape, alignment angle, flow depth and flume slope. The pattern of local scour were measured and analyzed the abutments which are rectangular, sharp, chamfered rectangular and ablong nose shapes. The experiments were carried out with varing the flume slope and alignment algle increasing flow depth every step in 1cm for four abutment types on the live-bed scour conditions. The flume slope and alignment angle were varied in five cases : for latter 30 $^{\circ}$, 60 $^{\circ}$, 90 $^{\circ}$, 120 $^{\circ}$ and 150 $^{\circ}$, for former 0.01%, 0.03%, 0.05%, 0.1% and 0.2%. The maximum scour depths were analyzed for the shaped of abutment nose with rectangular, ablong, chamfered rectangular and sharp in order. The results of the experiments show that the scour depth varies not only with abutment nose shapes and alignment angle but also with the flow depth and flume slope.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.507-520
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• 2003

A V-shaped riffle is an artificial hydraulic structure haying two wings from the streamside with a narrow opening in between. It is usually made of crushed stones or large boulders. It limits channel width and accelerates the flow through the constricted section causing a local scour just downstream. The V-shaped riffle provides with a unique aquatic habitat by forming a pool and sandbars around the pool edge, increasing local morphologic, hydraulic and sedimentological diversity. This study investigates experimentally the scour characteristics of the V-shaped riffle in the sandbed stream and proposes a predictive equation for the scour. Total 45 cases of experiments were conducted to examine the effect of hydraulic factors and configuration of V-shaped riffle on the geometry of scour holes. From the comparison of the experimental results of this study with the predictive equation of spur dike by Breusers and Raudkivi(1991), it is found that their predictive equation of spur dike underestimates the maximum scour depth downstream of the V-shaped riffle. h new predictive equation for the maximum scour depth was developed using the non-dimensional hydraulic and geometrical variables. The parameters used in the proposed equations were determined using the experimental data. The analysis reveals that the scour depth is dependent dominantly on the Froude number at the opening of the V-shaped riffle, while the angle of riffle and the opening width also affect the scour depth. The proposed equation for the scour of V-shaped riffle well agrees with the experimental data. It can be used for estimating the scour of the V-shaped riffle in sandbed streams.

• Ocean Systems Engineering
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• v.2 no.4
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• pp.257-269
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• 2012

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around spherical bodies exposed to long-crested (2D) and short-crested (3D) nonlinear random waves can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall (2000) wave crest height distribution representing both 2D and 3D nonlinear random waves, and using the regular wave formulas for scour and self-burial depths by Truelsen et al. (2005). An example calculation is provided.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.583-592
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• 2006

There has been debated on the fact that a scour hole produced by the construction of a groyne has environmental benefits such as provision of diverse underwater habitats and shelter for fish in the event of flooding. Therefore researches are focusing on the scour field around the groyne area beyond the existing safety issues. The scour area on aquatic habitats would format many form on groyne conditions so that the analysis of scour area is strongly required. This study conducted the experiments on permeability and installation angle of groyne and suggested the data for groyne selection in environmental point as analyzing scour area. The physical modeling was performed in different permeability (0%, 20%, 40%, 60%, 80%) and installation angle of groyne ($60^{\circ},\;90^{\circ},\;120^{\circ}$). As the result of the study, scour area and scour depth at maximum scour condition was revealed for each case and suggested the differences according to experiment conditions.

• Ocean Systems Engineering
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• v.6 no.2
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• pp.161-189
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• 2016

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around a vertical pile exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (2002). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases on mild slopes are also suggested.

• Ocean Systems Engineering
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• v.7 no.3
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• pp.275-298
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• 2017

This paper provides a practical stochastic method by which the maximum equilibrium scour depth below a pipeline exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (1996). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases for random waves alone are also suggested.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.373-381
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• 2015

As offshore structures such as offshore wind and offshore platforms have been installed frequently in ocean, scour effects are considered important. To test the scour effect, numerical simulation of scour has been carried out. However, the test was usually conducted under the uni-directional flow without bi-directional current flow in western sea of Korea. Thus, in this paper, numerical simulations of scour around offshore jacket substructure of HeMOSU-1 installed in western sea of Korea are conducted using FLOW-3D. The conditions are uni-directional and bi-directional flow considering tidal current. And these results are compared to measured data. The analysis results for 10,000 sec show that under uni-directional conditions, maximum scour depth was about 1.32 m and under bidirectional conditions, about 1.44 m maximum scour depth occurred around the structure. Meanwhile, about 1.5~2.0 m scour depths occurred in field observation and the result of field test is similar to result under bi-directional conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.2
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• pp.297-306
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• 2019

Since the centrifugal force acts on the flow in the curved channel, a transverse water surface gradient occurs and the thalweg is biased toward the outer bank. The submerged vanes may be used to solve various engineering problems of the curved channels. In order to analyze the influence of an attack angle and the distance between the vane arrays on the river bed variation and the superelevation in a bend, movable bed hydraulic experiments were conducted in a $90^{\circ}$ curved rectangular channel of a small-size gravel bed. Installing the submerged vanes in the bend increases the maximum scour depth. But if vanes are installed in a uniform obtuse angle, the scour depth may be reduced. If the flow rate in the channel bend with vanes equals to the channel forming discharge, the location of the maximum scour depth moved to the downstream and the superelevation increased. However if the flow rate is smaller than that, the location of the maximum scour depth moved upstream and the superelevation decreased. The channel bed change and the superelevation due to the installation of the submerged vanes have been dependent on the interaction of the attack angle, the flow rate, and the distance between the arrays.

• Journal of Korea Water Resources Association
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• v.37 no.9
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• pp.781-787
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• 2004

The variation of channel bed which shows the complex hydraulic characteristics at channel junction was investigated by variation of discharge ratio and location of pier. As discharge ratio increase, the depth and width of erosion region become bigger to point of 63% of channel width in case of 1:0.5 discharge ratio. It was observed that the maximum scour depth at the point of 0.5 times of the channel width in the channel junction as 2.5 times bigger than straight channel. It means that the maximum scour depth at the channel junction is 2 times greater than by experimental formulas which are widely used in practical engineering, location of pier should be determined when it is installed in channel junction.