• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.497-507
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• 2020

Two-dimensional laboratory experiments were conducted in a wave flume to investigate the wave transmission phenomena of rubble-mound type submerged structures armored with Tetrapods. Different experimental conditions were included by considering relative crest depth, relative freeboard, relative crest width, wave steepness, and so on. An empirical formula was proposed to predict the wave transmission coefficients over various specifications and structural designs of the partial perforated (rubble-mound) type submerged structure from the experimental results. The proposed formula successfully predicted the wave transmission coefficients. In this study, the proposed empirical formula of the wave transmission over the rubble-mound type submerged structure was improved from the existing formula.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.219-227
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• 2021

Numerical simulation with Hwang's scheme, which can analyze shallow-water flow over discontinuous topography, was compared with a laboratory experiment of flooding on a perpendicular floodplain with dam-break flows. The simulation results were in good agreement with the results measured in an experimental flume with a reservoir, channel, and floodplain. The wetting and drying process on a perpendicular floodplain with a dam-break flow was particularly well simulated. The difference in simulation results according to the type of flow resistance was insignificant. The results of this study are expected to improve the accuracy of predicting inundation in urban rivers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.6
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• pp.593-601
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• 2020

Two-dimensional laboratory experiments were conducted in a wave flume to investigate the wave transmission phenomena of impermeable-type submerged structures armored by concrete blocks. Different experimental conditions were included by considering relative crest depth, relative freeboard, relative crest width, wave steepness, and so on. An empirical formula was proposed to predict the wave transmission coefficients over various specifications and structural designs of the impermeable submerged structure from the experimental results. The proposed formula successfully predicted the wave transmission coefficients. Therefore, in this study, the proposed empirical formula of the wave transmission over an impermeable submerged structure was improved from the existing formula.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.359-368
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• 2010

This paper describes the generation and propagation of internal solitary wave in a two-layer fluid system by numerical analysis. Characteristics of interfacial soliton such as wave type, wave height, wave celerity are investigated numerically with respect to an extent of initial disturbance, fluid thicknesses of the two fluids and etc. The difference between the internal wave propagation on sloping beach and flat bottom was also examined. Laboratory experiments were conducted in the wave flume and compared with the results of numerical computation for verification.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.375-379
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• 2016

Recently derived energy dissipation equation by Chamani(2008) and the profile function of the free overfall by Marchi(1993) were verified with present experiment data. The experiment was conducted in hydraulic laboratory, Hanyang University where the flume is 7m long and 0.44m wide, and the height of the drop structure is 0.205m. Water depth and free overfall profile data were collected using an ultra sonic distance sensor and photographic images. The time-averaged water depth data and the free overfall profile were analyzed to examine the energy dissipation pattern over the drop structure

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.52-60
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• 2008

This study investigates the applicability of CADMAS-SURF (Super Roller Flume for Computer Aided Design of a MArtime Structure) code basal on the Navier-Stokes solver to predict bore phenomena. The time variation of ware levels and velocities due to the bore propagation were computed for the different bore strength conditions. In order to verify the numerical results by CADMAS-SURF, laboratory experiments were also performed, using the DPIV and LDV measuring system. The numerical results were compared to the experimental data and the analytical predictions by the NSC method basal on fully nonlinear shallow-water theory by the method of characteristics. It appears that the CADMAS-SURF slightly overestimated the water-surface level measured by the laboratory experiments and its discrepancy becomes prominent as the bore strength increases. The predicted propagation speed for a bore was also slaver than that by the experiment and NSC method. However, the temporal variations in velocities were in relatively good agreement with the experimental data for all cases, except for overshooting and undershooting in the front face of a bore, which may be derived from the numerical instability. Further, CADMAS-SURF successfully simulated the decrease in the water level and velocity caused by the effects of negative waves reflected from the upstream end wall.

• Water Engineering Research
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• v.1 no.2
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• pp.95-105
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• 2000

A method is presented which enables easily the computation of the suspended sediment discharge as the mean sediment concentration and mean flow velocity. This method has significant advantages over the traditional method, which principally depend on a set of measured concentration data. The method is based on both a new sediment concentration and mean sediment concentration equations which have been derived from the entropy concept used in statistical mechanics and information theory: (1) The sediment concentration distribution equations derived, are capable of describing the variation of the concentration in the vertical direction. (2) The mean concentration equation derived, is capable of calculating easily the mean concentration by using only one measured concentration in open channel. The present study mainly addresses the following two subjects : (1) new sediment concentration and mean sediment concentration equations are derived from the entropy concept : (2) An efficient and useful method of suspended sediment-discharge measurements is developed which can facilitate the estimation of suspended sediment-discharge in open channel. Flume and laboratory data are used to carry out the research task outlined above. An efficient method for determining the suspended sediment-discharge in the open channel has been developed. The method presented also is efficient and applicable in estimating the sediment transport in rivers and the sediment deposit in the reservoirs, and can drastically reduce the time and cost of sediment measurements.

• Water Engineering Research
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• v.2 no.4
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• pp.243-259
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• 2001

Local phenomena around bridge piers and abutments are generally considered to be similar, nevertheless the presence of the incoming boundary layer on the side wall in the abutment case generates extra pressure gradients and consequently a more complex vortex pattern. In the literature, experimental data for bridge abutments are relatively scarce; in particular almost no data are available for the time evolution of the scour. In this work we present the results of several long duration (3 days longrightarrow5weeks) clear water scour laboratory tests around bridge abutments; the time evolution of the erosion process is analysed with respect to local and global characteristic values (maxima, volume, hole shape). In particular we analyse the effect of the constriction ratio b/B between the transversal obstacle dimension and the flume width: in many practical situations abutments (or piers) obstruct a significant portion of the channel, so that the average acceleration due to constriction is expected to increase the scour effects of the local acceleration around the obstacle. Measured values for maximum scour are poorly predicted by literature formulas. Scour depths are positively correlated with the constriction ratio, but increases are smaller than expected from literature indications. Experimental results show that models for bridge piers cannot be directly applied to abutments; in particular, time scales for the latter are significantly larger than for piers.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.14-21
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• 2011

The purpose of this study is to quantify the erosional parameters, such as the critical shear stress for erosion and the erosion rate coefficient for cohesive sediments from the Mokpo coast. Using Chonbuk annular flume, five erosion tests were conducted under the uniform bed condition but a different bed density respectively. Erosion test results for Mokpo sediments have shown increases in the range of $0.16{\sim}0.43\;N/m^2$ but decreases exponentially in the range of $272{\sim}4.64\;mg/cm^2{\cdot}hr$ for the given bed shear stress of $1.14{\sim}1.34\;g/cm^3$. The erosional parameters of Mokpo sediments are found to vary remarkably in quantity compared with those for cohesive sediments from other sites. On the whole, the value of Mokpo coast sediments appears to be similar to Kunsan sediments but smaller than Saemankeum and Okeechobee sediments. On the other hand, Mokpo sediments have been shown to be larger than Saemankeum and Okeechobee sediments but smaller than Kunsan sediments.

• Ocean and Polar Research
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• v.31 no.4
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• pp.389-399
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• 2009

Subsurface pressure gauge has many advantages in measuring a wide range of wave spectra in coastal waters from wind waves to long waves. However, a shortcoming of the gauge is related to the difficulties in recovering surface wave spectra from subsurface pressure records. In this study, the effect of current on the pressure transfer function of the pressure gauge, and hence on the surface wave energy spectrum, was investigated by analyzing the subsurface pressure data based on the linear wave theory. For this purpose, laboratory experiments were carried out in a wave-current flume. Subsurface pressure records, as well as the surface elevation data, were obtained simultaneously under different wave and current conditions. Pressure transfer functions were obtained and compared with those estimated from the linear wave theory, both with and without inclusion of the current-effect. It was established that wave spectra obtained from subsurface pressure gauge were in closer agreement with those from surface wave gauge when current-effect on the pressure transfer function was taken into consideration for analysis.