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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 27, Issue 6D - Nov 2007
Volume 27, Issue 6C - Nov 2007
Volume 27, Issue 6B - Nov 2007
Volume 27, Issue 6A - Nov 2007
Volume 27, Issue 5D - Sep 2007
Volume 27, Issue 5C - Sep 2007
Volume 27, Issue 5B - Sep 2007
Volume 27, Issue 5A - Sep 2007
Volume 27, Issue 4D - Jul 2007
Volume 27, Issue 4C - Jul 2007
Volume 27, Issue 4B - Jul 2007
Volume 27, Issue 4A - Jul 2007
Volume 27, Issue 3D - May 2007
Volume 27, Issue 3C - May 2007
Volume 27, Issue 3B - May 2007
Volume 27, Issue 3A - May 2007
Volume 27, Issue 2C - Mar 2007
Volume 27, Issue 2A - Mar 2007
Volume 27, Issue 2D - Mar 2007
Volume 27, Issue 2B - Mar 2007
Volume 27, Issue 1D - Jan 2007
Volume 27, Issue 1C - Jan 2007
Volume 27, Issue 1B - Jan 2007
Volume 27, Issue 1A - Jan 2007
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Simulation of Instantaneous Injection for Numerical Simulation of Pollutant Mixing in the River Using Source Function
Seo, Il-Won ; Lee, Myung-Eun ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 1~8
Appropriate intial and boundary condition at the numerical simulation of river mixing with respect to instantaneously injected mass is studied here. Theoretical analysis of initially injected mass is achieved through one-dimensional analytic solution, and the proper numerical approximation of injection condition is proposed. For 2D expansion, source term constitute of spatial and temporal delta function is used to describe injected mass and finite element method is used as a descretization method. Simulation results showed that the source function model can provide more efficient and accurate method for the problem of instantaneously injected mass.
A Study on the Performance of Index Flood Method Based on Monte Carlo Simulation
Kim, Kyung-Duk ; Heo, Jun-Haeng ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 9~20
In this study, we investigate the performance of the index flood method for 4 regions whose specifications are representative of annual maximum rainfall data in Korea. For this purpose, the Monte Carlo simulation was performed to investigate the influence on the accuracy of quantile estimates depending on the at-site and regional frequency analyses, sample size, inter-site dependence, heterogeneity, and applied frequency distributions. As the results, index flood method is more accurate than at-site frequency analysis in regions with moderate amounts of heterogeneity, inter-site dependence, and mis-specification of the applied frequency distributions. Heterogeneity increases the relative bias of estimates for the case of at-site analysis not typical case of regional one as a whole. Inter-site dependence increases the variability of estimates but has little effect on the relative bias. And small amount of inter-site dependence may be unimportant in regional frequency analysis. As the nonexceedance probability is increased, the advantage of index flood method over at-site frequency analysis is getting increased. Also, it is founded that the mis-specification of the frequency distribution is more important than heterogeneity as a source of error for large return period.
Evaluating Coefficient of Transverse Dispersion Induced by Shear Flow
Baek, Kyong-Oh ; Seo, Il-Won ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 21~28
A mathematical approach on the two-dimensional dispersion induced by the shear flow was reviewed, and previous works for evaluating dispersion coefficients by theoretical methods were summarized. Based on the review, new equation, which can be widely used, for the transverse dispersion coefficient was developed. The new equation was verified with tracer data sets which had been obtained from laboratory experiments conducted in unlike meandering channels. The results of verification showed that the new equation agreed better with the observed transverse dispersion coefficient than previous works because it considered appropriately effects of the shear flow. Moreover, the equation had high applicability to natural rivers due to its simple form resulting from a linear profile of the shear flow. Although it was not validated in natural streams owing to lack of field data, the equation had little differences compared with existing empirical equations derived from field data.
Temporal Variation of Local Scour Depth around a Bridge Pier
Lee, Seung-Oh ; Lee, Jin-Woo ; Cho, Yong-Sik ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 29~35
The relationship between the flow intensity, defined as the ratio of approach flow velocity to critical velocity of bed materials, and the dimensionless time, tVc/y1, is investigated based on experimental data form the literature and this study. The modified formula for the equilibrium time scale is also presented. The root mean square error (RMSE) and the discrepancy ratio (r), defined as the ratio of the calculated value to the observed value, are employed for the quantitative comparison between the original and modified formula. It is observed that the scouring rate in front of a bridge pier becomes independent of the flow intensity for V1 / Vc > 0.75. While the relative sediment size, b/d50, only weakly influences the rate of scouring, the equilibrium scour depth itself is highly affected by the value of the relative sediment size. It is the effect of this independent variable about which the least is known or understood either for predicting scour depths or selecting the appropriate sediment size in laboratory experiments of scour. Therefore, in order to compare the equilibrium scour depth between laboratory experiments and field in detail, more consideration of the effect of b/d50 on scour depth should be required.
An Experimental Study for Analysis of Interception Efficiency at Transverse Grate Inlets in Steep Local Roads
Kim, Jung-Soo ; Kim, Jea-Kwon ; Lee, Jong-Tae ; Yoon, Sei-Eui ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 37~44
The grate inlets are designed in according to the discharge over a street in general. However, the discharge that was not intercepted due to the steep local road causes inundation over the main street. Therefore, it is necessary to analyze the flow characteristics and interception capacity at transverse grate inlets in steep local roads. Hydraulic experimental apparatus which can be changed the longitudinal slopes (2~10%) of street, the sizes (20~50 cm) and the types (TYPEI, II) of grate inlet was installed for this study. The range of the experimental discharges were from 2 l/sec to 24 l/sec. As the longitudinal slopes of local road increase over the 4%, the interception capacities of transverse grate inlets decreases due to water membrane phenomena rather than splash-over one. The interception discharges of transverse grate inlets per unit width changing the longitudinal slope of local road were calculated by the hydraulic experimental results. This interception discharges per unit width could be applied to decide the type, the length and the install space of the transverse great inlets in steep local roads.
Development of Statistical Seasonal Rainfall Model Considering Climate Information and Typhoon Characteristics
Kwon, Hyun-Han ; Moon, Young-Il ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 45~52
It is now widely acknowledged that climate variability modify hydrological frequency. However, traditional hydrological frequency analysis is not able to consider the effects on the exogenous factors. Because a traditional assumption underlying flood frequency analysis is that the underlying stochastic process is stationary in time. With regard to these points, this study is not only to consider exogenous factors which can influence on seasonal rainfall but also to provide the occurrence probability of a 10-year return period rainfall by employing hierarchical Bayesian multiple logistic regression model. The sea surface temperature, the GCM ensemble rainfall prediction and the characteristics of typhoon which can affect Korea are considered as potential predictors. It was found that those predictors are significantly correlated with exceeding 10-year return period rainfall. Given posterior distributions of parameters from Bayesian approach, the low pressure depression time and the SSTs relatively play an important role in both Seoul and Mokpo. Hierarchical Bayesian logistic model shows good performance in terms of classifying extreme events. The model indicates that the right classification rate is approximately 93% in both Seoul and Mokpo.
Characteristics of Flow Duration Curve According to the Operation of Multi-purpose Dams in the Han-River Basin
Kim, Nam-Won ; Lee, Jeong-Eun ; Lee, Byong-Joo ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 53~63
Many dams were constructed for the effective water resources management. Especially multi-purpose dams located in Han-river basin that provide capital region (Gyeonggi, Gangwon, Seoul etc.) with valuable water source. The purpose of the present study was to evaluate the changes of flow duration characteristics of the Paldang Dam basin due to operations of the Soyang and Chungju multipurpose dams. A semi-distributed watershed model, SWAT-K, was used in order to generate regulated and unregulated daily streamflows upstream of Paldang Dam. The reservoir operation module in SWAT-K was modified from original module in SWAT for modelling parallel multi-reservoir operations appropriately. Simulated flow regulated by the Soyang, Chungju, and Hwacheon dams was calibrated by comparison with the observed inflow data at Paldang reservoir. The flow pattern analyses by using this calibrated system show the entire effect of Soyang and Chungju multipurpose reservoirs is the storage capacity of 21.6 billion cubic meters/year for 54 days during flood season. For Soyang reservoir, the stored quantity is approximately 9.1 billion cubic meters/year which was stored for 64 days. For Chungju reservoir, the stored quantity is approximately 12.5 billion cubic meters/year which was stored for 28 days. This study is the first attempt to evaluate the flow pattern characteristics by using simulated flow according to dam operation. More accurate analysis is expected to reevaluate the operating status of multipurpose reservoirs in Korea.
Optimal Multi-reservoir System Operation using Fuzzy DP (I) - Development of Fuzzy DP Method
Yi, Jae-Eung ; Choi, Sung-Gyu ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 65~70
In Korea, spring drought and summer flood occurs repeatedly almost every year because of climate change. Accordingly, the efficient water resources management should be emphasized more and more. It is necessary to obtain the similar effects such as new water resources development by reducing the wasted water like unnecessary spillway release and by emphasizing the effective water use like optimal reservoir operation. Fuzzy dynamic programming has the capability of representing uncertainty of reservoir operation and developer's priority efficiently. Also, it can find the optimal solution under given objectives and constraints. Fuzzy dynamic programming is more elastic approach to be applied for fuzzy goals and constraints than general dynamic programming. Solutions for these kinds of problems are presented by fuzzy dynamic programming using fuzzy set theory and membership function. It is expected that the results of this study can be used as a guideline of optimal reservoir operation and evaluation of water resources in basin.
Optimal Multi-reservoir System Operation using Fuzzy DP (II) - Application for Multipurpose Dam
Yi, Jae-Eung ; Choi, Sung-Gyu ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 71~77
Variability of available water resources is increased because of frequent climate change. Since it is difficult to construct additional dams and to operate them reliably, the existing dams are operated conservatively. So, it's required to operate water resources projects effectively. In this study, the fuzzy DP model is developed by constructing the adequate membership functions considering sufficient storage, water supply, flood control, hydropower and changing priority on user's demands, Also, the superiority of optimal reservoir operation is verified by comparing the historical operation of Soyang reservoir with the optimal operation using the developed fuzzy DP model. Fuzzy DP model has advantages of evaluating the degree of satisfaction for fuzzy goals and fuzzy constraints, and controlling priority of constraints compared to the general optimization methods. It is expected that the result of this study can be used for a guideline of optimal reservoir operation and evaluation of basin water resources.
Experimental Investigation of Breaking Criteria of Wind-Generated Deepwater Waves
Oh, Sang-Ho ; Suh, Kyung-Duck ; Natsuki Mizutani ; Noriaki Hashimoto ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 79~90
In a wind wave flume, waves were generated using three different wind speeds and measured at two locations to obtain wave trains of no, intermittent, or frequent breaking. Water particle movement and free surface elevation were measured simultaneously using a PIV system and a wave gauge, respectively. For wind waves, not all the waves measured at a fixed location are breaking waves, and the breaking of a larger wave is not guaranteed. However, the larger the wave height, the larger the probability of breaking. In order to take as many breaking waves as possible for the cases of frequent breaking, we used the waves whose heights were close to the highest one-tenth wave height. The experimental results showed that the geometric or kinematic breaking criteria could not explain the occurrence of breaking of wind waves. On the other hand, the vertical acceleration beneath the wave crest was close to the previously suggested limit value, -0.5 g, when frequent breaking of large waves occurred, indicating that the dynamic breaking criterion would be good for predicting wave breaking of deepwater wind waves.
Dispersion-Corrected Finite Difference Model for Simulation of Tsunami Propagation over Slowly Varying Depth
Yoon, Sung-Bum ; Lim, Chae-Ho ; Bae, Jae-Seok ;
Journal of The Korean Society of Civil Engineers, volume 27, issue 1B, 2007, Pages 91~99
An explicit finite-difference numerical model is developed for the simulation of tsunami propagation over a slowly varying water depth. In the present model the numerical dispersion induced by the truncation error of numerical scheme is minimized by employing a dispersion-correction parameter determined based on time step, grid size and local water depth. The present model employs a linear Boussinesq-type wave equation that can be solved more easily than the conventional Boussinesq equations. In order to verify the present model the propagation of tsunamis is simulated for the cases of a plane slope and a submerged circular shoal. The numerical results are compared with the numerical solutions of the linearized Boussinesq equations. The comparisons give reasonable agreements between two solutions. However, the computational efficiency is significantly improved when the present model is used.