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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Society of Civil Engineers
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Korean Society of Civil Engeneers
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Volume & Issues
Volume 26, Issue 6D - Nov 2006
Volume 26, Issue 6C - Nov 2006
Volume 26, Issue 6B - Nov 2006
Volume 26, Issue 6A - Nov 2006
Volume 26, Issue 5D - Sep 2006
Volume 26, Issue 5C - Sep 2006
Volume 26, Issue 5B - Sep 2006
Volume 26, Issue 5A - Sep 2006
Volume 26, Issue 4D - Jul 2006
Volume 26, Issue 4C - Jul 2006
Volume 26, Issue 4B - Jul 2006
Volume 26, Issue 4A - Jul 2006
Volume 26, Issue 3D - May 2006
Volume 26, Issue 3C - May 2006
Volume 26, Issue 3B - May 2006
Volume 26, Issue 3A - May 2006
Volume 26, Issue 2D - Mar 2006
Volume 26, Issue 2C - Mar 2006
Volume 26, Issue 2B - Mar 2006
Volume 26, Issue 2A - Mar 2006
Volume 26, Issue 1D - Jan 2006
Volume 26, Issue 1C - Jan 2006
Volume 26, Issue 1B - Jan 2006
Volume 26, Issue 1A - Jan 2006
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Extraction of Nonlinear Dynamical Component by Wavelet Transform in Hydro-meteorological Data
Jin, Young-Hoon ; Park, Sung-Chun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 439~446
In the present study, we applied wavelet transform to decompose the hydro-meteorological data such as precipitation and temperature into the components with different return periods with a primary objective for extraction of nonlinear dynamical component. For the transform, we used the Daubechies wavelet of order 9 ('db9') as a basis function. Also, we applied the correlation dimension analysis to determine whether or not the detail and approximation components at the respective decomposition stage with the increasing of scale in the wavelet transform reveal the nonlinear dynamical characteristics. In other words, we proposed the combined use of the wavelet transform and the correlation dimension analysis as methodology to extract the nonlinear dynamical component from the hydro-meteorological data. The derived result has shown the method proposed in the present study is suitable for the segregation and extraction of the nonlinear dynamical component which is, in general, difficult to reveal by using the raw data.
Numerical Simulation of Depth-Averaged Flow with a CDG Finite Element Method
Kim, Tae Beom ; Choi, Sung-Uk ; Min, Kyung Duck ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 447~457
This paper presents a numerical model for the simulations of 2D depth-averaged flows. The shallow water equations are solved numerically by the Characteristic Dissipative Galerkin (CDG) finite element method. For validation, the developed model is applied to the hydraulic jump. The computed results are compared with the analytical solution, revealing good agreement. In addition, flow in a contracting channel showing standing waves is simulated. The calculated water surface profile appears to be qualitatively consistent with the observed data. The foregoing results indicate that the model is capable of simulating the abrupt change in flow field. Next, the model is applied to the flow in a
curved channel. The simulated results show that the velocity near the inner bank is faster than that near the outer bank and the water depth near the inner bank is shallower than that near the outer bank. However, the simulated results show that the velocity distribution across the channel is almost uniform in the bend except the reach close to the end of the bend. This is due to the limitation of the governing equations in which the transverse convection of momentum by the secondary flows along a channel bend is not taken into account.
Hydraulic and Numerical Model Experiments of Circulation Water Intake for Boryeong Thermal Power Plant No. 7 and No. 8
Yi, Yong-Kon ; Cheong, Sang Hwa ; Kim, Chang Wan ; Kim, Jong Gang ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 459~467
In this study, hydraulic and numerical model experiments were performed to analyze and improve the effects of flow-rate increase in the intake canal of Boryeong Thermal Power Plants on the flow condition in the circulation water pump (CWP) chambers. Based on the numerical simulation results, when the flow-rate increased in the circulation water intake canal, the velocity in the canal and vertical vorticities in the circulation water pump chambers increased and hence the vortex occurrence potential would be greatly increased. It was found by performing hydraulic model experiments that the velocity distribution near the bottom in the inlet of the circulation water pump chambers was highly non-uniform while the velocity distribution near the water surface was nearly uniform. To reduce the non-uniformity in the velocity distribution, triangular flow deflectors were devised. The installation of the flow deflectors in the inlet of circulation water pump chambers was successfully to reduce velocity non-uniformities and to remove flow reversal problems.
Flow Structure and Turbulence Characteristics in Meandering Channel
Seo, Il Won ; Lee, Kyu Whan ; Baek, Kyong Oh ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 469~479
In order to investigate characteristics of the primary flow and the secondary currents in meandering channels, the laboratory experiments were conducted in S-curved channels with angle of bend,
, and sinuosity of 1.52. The experimental conditions was decided varying average depth and velocity. Under these experimental conditions, spatial variations of the secondary currents in multiple bends were observed. The experimental results revealed that the distribution of primary flow in straight section is symmetric without respect to the experimental condition and the maximum velocity line of the primary flow occurs along the shortest path in experimental channel, supporting the result of previous works. The secondary currents in second bend became more developed than those in first bend. Particularly, the outer bank cell developed distinctively and the secondary current intensity was low at the straight section and high at the bends, periodically. Also, the secondary current intensity at the bends was as twice to three times as that at the straight section, and has its maximum value at the second bend. The turbulent flow characteristics of meandering channel was investigated with turbulent intensity of the primary flow and Reynolds shear stress. It was observed that the turbulent intensity is increasing when the velocity deviation of the primary flow is large whereas Reynolds shear stress increases when both the velocity deviation of the primary flow and the secondary current are large.
An Integrated Surface Water-Groundwater Modeling by Using Fully Combined SWAT MODFLOW Model
Kim, Nam Won ; Chung, Il Moon ; Won, Yoo Seung ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 481~488
This paper suggests a novel approach of integrating the quasi-distributed watershed model SWAT with the fully-distributed groundwater model MODFLOW. Since the SWAT model has semi distributed features, its groundwater components hardly considers distributed parameters such as hydraulic conductivity and storage coefficient. Generating a detailed representation of groundwater recharge, head distribution and pumping rate is equally difficult. To solve these problems, the method of exchanging the characteristics of the hydrologic response units (HRUs) in SWAT with cells in MODFLOW by fully combined manner is proposed. The linkage is completed by considering the interaction between the stream network and the aquifer to reflect boundary flow. This approach is provisionally applied to Gyungancheon basin in Korea. The application demonstrates a combined model which enables an interaction between saturated zones and channel reaches. This interaction plays an essential role in the runoff generation in the Gyungancheon basin. The comprehensive results show a wide applicability of the model which represents the temporal-spatial groundwater head distribution and recharge.
Risk of Flood Damage Potential and Design Frequency
Park, Seok Geun ; Lee, Keon Haeng ; Kyung, Min Soo ; Kim, Hung Soo ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 489~499
The Potential Flood Damage (PFD) is widely used for representing the degree of potential of flood damage. However, this cannot be related with the design frequency of river basin and so we have difficulty in the use of water resources field. Therefore, in this study, the concept of Potential Risk for Flood Damage Occurrence (PRFD) was introduced and estimated, which can be related to the design frequency. The PRFD has three important elements of hazard, exposure, and vulnerability. The hazard means a probability of occurrence of flood event, the exposure represents the degree that the property is exposed in the flood hazard, and the vulnerability represents the degree of weakness of the measures for flood prevention. Those elements were devided into some sub-elements. The hazard is explained by the frequency based rainfall, the exposure has two sub-elements which are population density and official land price, and the vulnerability has two sub-elements which are undevelopedness index and ability of flood defence. Each sub-elements are estimated and the estimated values are rearranged in the range of 0 to 100. The Analytic Hierarchy Process (AHP) is also applied to determine weighting coefficients in the equation of PRFD. The PRFD for the Anyang river basin and the design frequency are estimated by using the maximum rainfall. The existing design frequency for Anyang river basin is in the range of 50 to 200. And the design frequency estimation result of PRFD of this study is in the range of 110 to 130. Therefore, the developed method for the estimation of PRFD and the design frequency for the administrative districts are used and the method for the watershed and the river channel are to be applied in the future study.
Evaluation of Levee Reliability by Applying Monte Carlo Simulation
Jeon, Min Woo ; Kim, Ji Sung ; Han, Kun Yeun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 501~509
The safety of levee that depends on the river flood elevation has been regarded as very important keys to build up various flood prevention systems. However, deterministic methods for computation of water surface profile cannot reflect the effect of possible inaccuracies in the input parameters. The purpose of this study is to develop a methodology of uncertainty computation of design flood level based on steady flow analysis and Monte Carlo simulation. This study addresses the uncertainty of water surface elevation by Manning's coefficients, design discharges, river cross sections and boundary condition. Monte Carlo simulation with the variations of these parameters is performed to quantify the variations of water surface elevations in a river. The proposed model has been applied to the Kumho-river. The reliability analysis was performed within 38.5 km (95 sections) reach considered the variations of the above-mentioned parameters. Overtopping risks were evaluated by comparing the elevations of the flood condition with the those of the levees. The results show that there is a necessity which will raise the levee elevation between 1 cm and 56 cm at 7 sections. The model can be used for preparing flood risk maps, flood forecasting systems and establishing flood disaster mitigation plans as well as complement of conventional levee design.
Development of Urban Flood Analysis Model Adopting the Unstructured Computational Grid
Lee, Chang Hee ; Han, Kun Yeun ; Kim, Ji Sung ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 511~517
Flood damage is one of the most important and influential natural disaster which has an effect on human beings. Local concentrated heavy rainfall in urban area yields flood damage increase due to insufficient capacity of drainage system. When the excessive flood occurs in urban area, it yields huge property losses of public facilities involving roadway inundation to paralyze industrial and transportation system of the city. To prevent such flood damages in urban area, it is necessary to develop adequate inundation analysis model which can consider complicated geometry of urban area and artificial drainage system simultaneously. In this study, an urban flood analysis model adopting the unstructured computational grid was developed to simulate the urban flood characteristics such as inundation area, depth and integrated with subsurface drainage network systems. By the result, we can make use of these presented method to find a flood hazard area and to make a flodd evacuation map. The model can also establish flood-mitigation measures as a part of the decision support system for flood control authority.
Time Distribution Characteristics of an Annual Maximum Rainfall According to Rainfall Durations using Huff's Method
Lee, Jong-Kyu ; Chu, Hyun-Jae ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 519~528
In the construction of hydraulic structures deciding a design flood is one of the most important works. It should be especially noted that the time distribution of the design rainfall method makes a significant effect on the results of the design flood. Thus, choosing an appropriate time distribution method for the design rainfall is a very important process. In recent years, Huff's method is usually used in Korea. This method presents dimensionless rainfall-time cumulative curves, which are made through the analyses of storm data. In this study, the annual maximum rainfall data, from 1961 to 2004 were analyzed to make the dimensionless rainfall-time cumulative curves and hyetographs in Seoul. The results were compared with the "Regional Time Distribution of the Design Rainfall", (KICT, 1989 and MCT, 2000). As a result, the dimensionless rainfall-time cumulative curves are smoother than Huff's results when the duration of an annual maximum rainfall is short. In addition, the curves are similar with the Huff's results as the duration is longer.
Impact of Drag-Related Weighting Coefficients in Vegetated Open-Channel Flows
Kang, Hyeongsik ; Choi, Sung-Uk ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 529~537
This paper investigates the impacts of the drag-related weighting coefficients on mean velocity and turbulence structures. The transport equations for the Reynolds stress of vegetated open-channel flows are derived by using the temporal- and horizontal-averaging scheme. It is found that the total Reynolds stress of vegetated open channel flows consists of the Reynolds stress due to temporally fluctuating velocities and the Reynolds stress due to spatially fluctuating velocities. The drag-related weighting coefficient
for the total Reynolds stress component is found to be unit, while the coefficient for the Reynolds stress due to temporally fluctuating velocities can be negligible. This is the reason why very small weighting coefficients in previous studies yield very good agreements with measured data. In other words, the Reynolds stress due to spatially fluctuating velocities remains still unknown, especially due to the large number of measuring locations. Through a developed Reynolds stress model, vegetated open-channel flows are simulated and compared with measured data from the literature. Comparisons reveal that the computed mean flow and Reynolds stress structures are hardly affected by the drag-related weighting coefficients. However, the computed turbulence intensity profiles are significant different with the drag-related weighting coefficients. A budget analysis of the transport equations for the Reynolds stress component is carried to investigate why turbulence intensity is affected by the drag-related weighting coefficients.
Hydrodynamic Analysis of Two-dimensional Floating Breakwater in Weakly Nonlinear Waves
Lee, Jeongwoo ; Cho, Woncheol ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 539~549
The performance of a pontoon-type floating breakwater (FB) is investigated numerically with the use of a second-order time domain model. The model has been developed based on potential theory, perturbation theory and boundary element method. This study is focused on the effects of weakly nonlinear wave on the hydrodynamic characteristics of the FB. Hydrodynamic forces, motion responses, surface elevation, and wave transmission coefficient around the floating breakwater are evaluated for various wave and geometric parameters. It is shown that the second-order wave component is of significant importance in calculating magnitudes of the hydrodynamic forces, mooring forces and the maximum response of a structure. The weak non-linearity of incident waves, however, can have little influence on the efficiency of the FB. From numerical simulations, the ratio of draft and depth, the relationship of wave number and width are presented for providing an effective means of reducing wave energy.
Development of Practical Dispersion-Correction Scheme for Propagation of Tsunamis
Sohn, Dae-Hee ; Cho, Yong-Sik ; Ha, Tae-Min ; Kim, Sung-Min ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 551~555
In this study, new dispersion-correction terms are added to a leap-frog finite difference scheme for the linear shallow-water equations with the purpose of considering dispersion effects of the linear Boussinesq equations for propagation of tsunamis. The numerical model developed in this study is tested to the problem that the initial free surface displacement is a Gaussian hump over a constant water depth, and the predicted numerical results are compared with analytical solutions. The results of the present numerical model are accurate in comparison with those of existing models.
3-D Dispersive Transport Model for Turbidity Plume induced by Dredging Operation
Kang, See Whan ; Kang, In Nam ; Lee, Jung Lyul ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 557~562
In order to predict the dispersion of suspended sediment arising from dredging operation in port and navigation channel, a hybrid model for dispersive transport of turbidity plume was developed using Lee's(1998) hybrid method. Using hybrid modeling scheme advection-diffusion equation was solved by the forward particle-tracking method for advection process and by the fixed Eulerian grid method for diffusion process. To examine numerical model simulation in accuracy, the simulated results for 1-D, 2-D, and 3-D cases were compared with the analytical solutions including Kuo, et al's (1985) 3-D mathematical model. The model results were in a good agreement with the analytical solutions and mathematical model for the dispersion of turbidity plume.
The Phase Difference Effects on 3-D Structure of Wave Pressure Acting on a Composite Breakwater
Hur, Dong-Soo ; Yeom, Gyeong-Seon ; Bae, Ki-Seong ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 5B, 2006, Pages 563~572
In designing the coastal structures, the accurate estimation of wave forces on them is very important. Recently, the empirical formulae such as Goda formula are widely used to estimate wave forces, as well as 2-D hydraulic and numerical model tests. But, sometimes, these estimation methods mentioned above seem to be unreasonable to predict 3-D structure of wave pressure on the coastal structures with 3-D plane arrangement in the real coastal area. Especially, in case of consideration of phase difference at harbor and seaward sides of the large-sized coastal structures like a composite breakwater, it is easily expected that the real wave pressures on each section of coastal structure have 3-D distribution. A new numerical model of 3-D Large Eddy Simulation, which is applicable to permeable structure, is developed to clarify the 3-D structure of wave pressures acting on coastal structure. The calculated wave forces on 3-D structure installed on the submerged breakwater show in good agreement with the measured values. In this study, the composite breakwater is adopted as a representative structure among the large-sized coastal structures and the 3-D structure of wave pressures on it is discussed in relation to the phase difference at harbor and seaward sides of it due to wave diffraction and transmitted wave through rubble mound.