• 한국농공학회지
• /
• 제29권4호
• /
• pp.59-72
• /
• 1987

Although long-term runoff analysis is important as much as flood analysis in the design of water works, the technological level of the former is relatively lower than that of the latter. In this respect, the precise estimation model for the volume of successive runoff should he developed as soon as possible. Up to now, in Korea, Gajiyama's formula has been widely used in long-term runoff analysis, which has many problems in applying in real situation. On the other hand, in flood analysis, unit hydrograph method has been exclusively used. Therefore, this study aims at trying to apply unit hydrograph method in long-term runoff analysis for the betterment of its estimation. Four test catchment areas were selected ; Maesan area in Namlum river as a representative area of Han river system, Cheongju area in Musim river as one of Geum river system, Hwasun area in Hwasun river as one of Yongsan river system, and Supyung area in Geum river as one of Nakdong river system. In the analysis of unit hydrograph, seperation of effective rainfall was carried out firstly. Considering that effective rainfall and moisture condition of catchrnent area are inside and outside of a phenomenon respectively and the latter is not considered in the analysis, Initial base flow(qb)was selected as an index of moisture condition. At the same time, basic equation(Eq.7) was established, in which qb can take a role as a parameter in relating between cumulative rainfall(P) and cumulative loss of rainfall(Ld). Based on the above equation, computer program for estimation model of qbwas seperately developed according to the range of qb, Developed model was applied to measured hydrographs and hyetographs for total 10 years in 4 test areas and effective rainfall was estimated. Estimation precision of model was checked as shown in Tab- 6 and Fig.8. In the next stage, based on the estimated effective rainfall(R) and runoff(Qd), a runoff distribution ratio was calculated for each teat area using by computerised least square method and used in making unit hydrographs in each test area. Significance of induced hydrographs was tested by checking the relative errors between estimated and measured runoff volume(Tab-9, 10). According to the results, runoff estimation error by unit hydrograph itself was merely 2 or 3 %, but other 2 or 3 % of error proved to be transferred error in the seperation of effective rainfall. In this study, special attentioning point is that, in spite of different river systems and forest conditions of test areas, standardized unit hydrographs for them have very similar curve shape, which can be explained by having similar catchinent characteristics such as stream length, catchinent area, slope, and vegetation intensity. That fact should be treated as important factor ingeneralization of unit hydrograph method.

• 한국물환경학회지
• /
• 제39권6호
• /
• pp.439-450
• /
• 2023

The Yeongsan River, a major water resource for Jeollanam-do, that is adjacent to industrial complexes and agricultural areas, is exposed to water pollution. Therefore, it is necessary to investigate the impact of water pollution incidences and prepare response systems for river environment safety for other water resources in the future. Environmental Fluid Dynamics Code (EFDC) was applied to the mainstream of the Yeongsan River where residential, commercial, and agricultural areas are located to analyze the behavior of pollutants conducting the scenario analysis. Considering the pollutants that affected the study area, two pollutants, oil and benzene, with different physical and chemical characteristics were selected for the analysis. As a result of comparing the actual and simulated values of the water elevation, temperature, and flow rate, it was confirmed that the model adequately reproduced the hydraulic characteristics of the Yeongsan River. The oil flow dynamics showed that an increase in flow rate led to reduction in the maximum height of the slick. Notably, the behavior of the oil was predominantly influenced by the wind conditions. In the case of benzene, lower flow scenarios exhibited decreased arrival times and residence times accompanied by an elevation in the maximum concentration levels. From the results of pollutant behavior in the study area, it is feasible to utilize the section of tributary confluence for collection and the weir area for dilution. This study enhances the understanding of the pollutant's behavior with different characteristics and develops effective control systems tailored to the physicochemical attributes of pollutants.

• 한국공간구조학회논문집
• /
• 제6권1호
• /
• pp.111-115
• /
• 2006

방풍팬스의 설치에 의한 저층건물 주변의 풍압특성을 분석하기 위하여 풍압실험을 실시하였다. 방풍팬스의 다공율은 0%와 20%을 중심으로 하였다. 방풍팬스와 저층건물의 거리는 1H-9H까지 범위안에서 측정을 하였다. 사용된 풍속은 6m/s로 일정하게 하였다. 저층건물의 측압공 위치는 정면과 측면 후면을 중심으로 총 54개를 측정하였다. 분석결과 다공률 20%일때는 측정거리 1H-3H일 때 다공률 40%일 때는 측정거리 4H-6H일 때 가장 효과적이었다.

• 한국환경복원기술학회지
• /
• 제25권6호
• /
• pp.65-75
• /
• 2022

Urban flood management(UFM) strategy ought to consider the connections and interactions between existing and new infrastructures to manage stormwater and improve the capacity to treat water. It is also important to demonstrate strategies that can be implemented to reduce the flow at flooding sources and minimize flood risk at critical locations. Although the general theory of spatial impact is popular, modeling guidelines that can provide information for implementation in real-world plans are still lacking. Under such background, this study conducted a modeling research based on an actual target site to confirm the hypothesis that it is appropriate to install green infrastructure(GI) in the source area and to take structural protection measures in the impact area, as summarized in previous studies. The results of the study proved the hypothesis, but the results were different from the hypothesis depending on which hydrological performance indicators were targeted. This study will contribute to demonstrating the effectiveness of strategies that can be implemented to reduce the flow at flooding sources and minimize the risk of flooding in critical locations in terms of spatial planning and regeneration.

• 한국지리정보학회지
• /
• 제13권4호
• /
• pp.50-66
• /
• 2010

본 논문에서는 보다 합리적이고 객관적인 토석류 방재대책 수립에 도움을 주기 위하여 고정밀 LiDAR DEM을 이용한 GIS 기반의 토석류 시뮬레이션 방법을 제시하였다. 매우 극단적인 산악지형 분포를 보이는 강원도 평창군 일원을 연구대상지역으로 설정하고, 유한차분법을 적용한 GIS 기반의 수치해석 프로그램을 이용하여 토석류의 발생 가능성을 시뮬레이션 하였다. 그 후 해석된 토석류 시뮬레이션 결과의 신뢰성을 검증하기 위하여 동일한 대상지역에 대하여 SINMAP 및 지형해석 방법에 의한 토석류 해석을 수행하고, 그 해석결과를 본 연구에서 제안된 GIS 기반의 토석류 시뮬레이션 결과와 비교 분석하였다.

• Journal of Ship and Ocean Technology
• /
• 제10권1호
• /
• pp.1-9
• /
• 2006

The resistance reduction by an air lubrication effect of a large air cavity covering the hull bottom surface and the similarity relations involved have been investigated with a series of towing tank tests of three geometrically similar models. The test results of geometrically similar models have indicated that a large air cavity was formed beneath the bottom having a backward-facing step by artificially supplying air is effective for resistance reduction. The areas of air cavity and the required flow rates of air are directly related to the effective wetted surface area. The traditional extrapolation methods seem to be applicable to the estimation of the resistance in the tested range if corrections are made to account the changes in the frictional resistance caused by the changes in the effective wetted surface area. To investigate the effectiveness of air lubrication in improving the resistance performance of a practical ship, a small test boat having a backward-facing step under its bottom has been manufactured and speed trials in a river have been performed. Air has been supplied artificially into the downstream region of the bottom step to form a large air cavity covering the bottom surface. The results have confirmed the practical applicability of air lubrication for the resistance reduction of a small high-speed boat.

• 대한불안의학회지
• /
• 제4권2호
• /
• pp.148-156
• /
• 2008

Objective : Although cognitive-behavior therapy (CBT) is effective in patients with panic disorder, its the-rapeutic mechanism of action in the brain remains unclear. This study was performed to investigate regional blood flow changes associated with successful completion of CBT in drug-naive patients with panic disorder. Method : The regional blood flow in 4 patients with panic disorder was compared to that in 11 healthy controls before and after a 12-week group CBT using $^{99m}Tc$-ECD SPECT imaging. Psychopathology was assessed using Panic Disorder Severity Scale. Data were analyzed using software for statistical parametric mapping (SPM2). Results : Before CBT, significantly decreased blood flow was found in the parietal and occipital area in panic patients than normal volunteers. In all the patients who showed remission after CBT, increased blood flow was detected in the right cingulate gyrus, left lingual gyrus, and left superior parietal lobule, whereas decreased blood flow was seen in the left inferior temporal gyrus. Conclusion : These results suggested that CBT is effective for panic disorder and change the activity of cingulate gyrus and left temporal gyrus, a part of the brain areas associated with fear in panic disorder.

• 설비공학논문집
• /
• 제16권6호
• /
• pp.589-598
• /
• 2004

Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

• Wind and Structures
• /
• 제27권4호
• /
• pp.213-221
• /
• 2018

In the desert and Gobi regions with strong wind and large sediment discharge, sand transporting engineering is more effective than sand blocking and sand fixing measures in sand prevention. This study uses the discrete phase model of 3D numerical simulation to study the motion trail, motion state and distribution rule of sand particles with different grain diameters when the included angle between the main shaft of the feather-row lateral transportation sand barrier and the wind direction changes, and conducts a comparison in combination with the wind tunnel test and the flow field rule of common sand barrier. According to the comparison, when wind-sand incoming flow passes through a feather-row sand barrier, sand particles slow down and deposit within the deceleration area under the resistance of the feather-row sand barrier, move along the transportation area formed by the transportation force, and accumulate as a ridge at the tail of the engineering. With increasing wind speed, the eolian erosion of the sand particles to the ground and the feather-row sand barrier is enhanced, and the sand transporting quantity and throw-over quantity of the feather-row sand barrier are both increased. When sand particles with different grain diameters bypass the feather-row sand barrier, the particle size of the infiltrating sands will increase with the included angle between the main shaft of the feather-row sand barrier and the wind direction. The obtained result demonstrates that, at a constant wind speed, the flow field formed is most suitable for the lateral transportation of the wind-drift flow when the included angle between the main shaft of the feather-row sand barrier lateral transportation engineering and the wind speed is less than or equal to $30^{\circ}$.

• 한국안전학회지
• /
• 제30권6호
• /
• pp.78-84
• /
• 2015

In order to increase the utilization of limited space in urban area, it can be a good solution to make use of underground space. For the last few decades, underground space systems, such as underground passages, subway stations, and underground shopping arcades, have been constructed in many cities all over the country. Despite of the advantages on the utilization of space in urban area, underground space systems have always been exposed to the risk of inundations resulted from severe rain storms. In this study, it has been examined to apply 2-D flow models (TUFLOW and FLUMEN) to establishing the preventive measures to the risk of flood. For the part with relatively complex configuration, such as a corridor junction, 2-D flow models present the detailed information about the effect of geometry on the inundation events and the temporal and spatial distribution of inundation over the space. From the result, it can be concluded that the 2-D flow model can be the effective implement for establishing the proper measure to the inundation on underground space systems, which generally have relatively long and narrow geometry with complex inner configuration.