개수로에서 흐름방향 유속의 횡분포 이론식에 기반한 종분산계수 개발 : I. 흐름방향 유속의 횡분포

백경오,Baek, Kyong Oh 한국수자원학회 2015 한국수자원학회논문집 Vol.48 No.4

The aim of this study is that a theoretical formula for estimating the one-dimensional longitudinal dispersion coefficient is derived based on a transverse distribution equation for the depth averaged stream-wise velocity in open channel. In "Part I. Theoretical equation for stream-wise velocity" which is the former volume of this article, the velocity distribution equation is derived analytically based on the Shiono-Knight Model (SKM). And then incorporating the velocity distribution equation into a triple integral formula which was proposed by Fischer (1968), the one-dimensional longitudinal dispersion coefficient can be derived theoretically in "Part II. Longitudinal dispersion coefficient" which is the latter volume of this article. SKM has presented an analytical solution to the Navier-Stokes equation to describe the transverse variations, and originally been applied to straight and nearly straight compound channel. In order to use SKM in modeling non-prismatic and meandering channels, the shape of cross-section is regarded as a triangle in this study. The analytical solution for the velocity distribution is verified using Manning's equation and applied to velocity data measured at natural streams. Although the velocity equation developed in this study do not agree well with measured data case by case, the equation has a merit that the velocity distribution can be calculated only using geometric data including Manning's roughness coefficient without any measured velocity data.

CFD모형을 활용한 저류배수터널에서 공기-물 분출 거동 해석

백경오,이찬웅,이동열,Baek, Kyong Oh,Lee, Chan Woong,Lee, Dong Yeol 한국수자원학회 2024 한국수자원학회논문집 Vol.57 No.11

극한 호우에 대비한 도시의 침수방지대책 중 하나로 지하 저류배수터널이 제안되고 있다. 이러한 터널 내 흐름은 초기에는 개수로 흐름으로 시작하여 이후에는 관수로 흐름으로 전환되면서 공기-물의 이상류 혼합 및 공기-물 분출 현상과 같은 복잡한 유체 역학적 거동을 보인다. 본 연구에서는 이러한 공기-물 혼합 흐름을 분석하는 데 적합한 3차원 CFD 모형인 Flow-3D를 선택하여 저류배수터널 내 공기-물 분출 현상을 중점적으로 살펴 보았다. 수치 모형의 검증을 위해 기존 실험 사례를 선택하여 공기-물 분출 현상을 재현하고 압력수두 변동을 비교하였다. 또한, 배기관을 통해 분출되는 공기와 물의 거동이 다양한 요소에 따라 어떻게 변화하는지 분석하였다. 본관 터널의 유량, 배기관의 직경, 배기관의 위치, 그리고 본관의 기울기 변화에 따른 공기-물 분출 현상의 양상을 분석한 결과, 본관 유량이 증가하고 기울기가 감소할수록 분출 현상이 빈번하게 발생하였다. 반면, 본관의 기울기가 급한 경우(2%), 공기-물 분출 현상이 발생하지 않았다. 배기관의 직경이 커질수록 분출이 상대적으로 더 빠르게 발생하였다. 배기관의 위치가 상류 또는 하류로 이동할 경우, 분출 현상은 일정한 규칙성 없이 다양한 양상을 보였다. As one of the flood prevention measures for urban areas against extreme rainfall event, underground storage and drainage tunnels have been proposed. The flow within these tunnels initially starts as open-channel flow and later transitions to pressurized flow, exhibiting complex hydrodynamic behaviors such as air-water mixture flow and geysering phenomena. In this study, the three-dimensional CFD model, Flow-3D, which is suitable for analyzing such air-water mixture flow, was selected to focus on investigating the geysering phenomenon in storage and drainage tunnels. To validate the numerical model, previous experimental case studies were selected to replicate the geysering phenomenon, and variations in pressure head were compared. Furthermore, this study examined how the behavior of air and water ejected through vent pipes varied depending on different factors. The patterns of the geysering were analyzed based on changes in the main tunnel's flow rate, vent pipe diameter, vent pipe location, and the slope of the main tunnel. Results showed that as the main tunnel flow rate increased and the slope decreased, the geysering occurred more frequently. Conversely, when the main tunnel had a steeper slope (2%), no geysering occurred. As the vent pipe diameter increased, geysering occurred relatively faster. When the vent pipe location was shifted upstream or downstream, the geysering pattern exhibited diverse behaviors without a consistent regularity.

8일 간격으로 부분 계측된 유량을 연속 일유량으로 확장하는 방법

백경오,임동희,Baek, Kyong-Oh,Yim, Dong-Hee 한국수자원학회 2012 한국수자원학회논문집 Vol.45 No.1

In this study, it was proposed that extension techniques of 8 day interval recorded stream-flow data which has been produced at the mouth of unit watersheds for TMDLs to daily one. The concept of this method was that the missing data at partial recording station was filled by using the daily data at a nearby, hydrologically similar streamgaging station. First, same day stream-flow was extracted from the daily stream-flow. Then, the extension equation was developed based on the sample data when the same day stream-flow from daily data and the partially recorded stream-flow was deeply related each other. The missing data was interpolated or extrapolated by the equation. Especially the maintenance of variance extension (MOVE) technique was used to derive the equation and was validated. Finally the 8-day interval recorded stream-flow at the mouth of unit watersheds in Han River Basin for TMDLs was extended to continuously daily data by using the method proposed in this study. And the low flow at each unit watershed was evaluated according to the flow-duration curve.

감조하천 홍수위 계산의 불확실성과 저감 대안 - 임진강 하류를 대상으로

백경오,권혁원,Baek, Kyong Oh,Kwon, Hyek Won 한국안전학회 2018 한국안전학회지 Vol.33 No.2

Compared with general rivers, fluctuations of the water level and the river bed are severe in the tidal river. In hydro-dynamic aspect, such fluctuation gives different river-bed data to us according to observing period. The time-dependent river-bed data and pre-estimation of the Manning's roughness coefficient which is the key factor of numerical modelling induces uncertainty of evaluating the design flood level. Thus it is necessary to pay more attention to calculate the flood level at tidal rivers than at general rivers. In this study, downstream of the Imjin River where is affected by tide of the West Sea selected as a study site. From the numerical modelling, it was shown that the unsteady simulation gave considerable mitigation of the water level from the starting point to 15 km upstream compared to the steady simulation. Either making a detention pond or optional dredging was not effective to mitigate the flood level at Gugok - Majung region where is located in the downstream of the Imjin River. Therefore, a more sophisticated approach is required to evaluate the design flood level estimation before constructive measures adopted in general rivers when establishing the flood control plan in a tidal river.

만곡수로에서 흐름방향에 따른 2차류의 변화량 산정식

백경오(Baek Kyong Oh),서일원(Seo Il Won),이규환(Lee Kyu Whan) 대한토목학회 2006 대한토목학회논문집 B Vol.26 No.4B

본 연구에서는 만곡수로에서 주 흐름방향에 따라 변화하는 2차류의 거동을 이론적으로 예측하기 위해 Odgaard(1986) 및 Chang(1988)의 제안을 바탕으로 새로운 방정식을 유도하였다. 개발된 이론식은 2차류의 횡방향 유속을 주 흐름 및 연직방향의 함수로 표현한다. 이를 검증하기 위해 실험실에 사행도가 각기 다른 두 개의 만곡수로를 제작하여 수리실험을 수행하였다. 수리실험결과를 제안된 이론식 및 기존 식과 비교해 보면, 제안된 식은 실측치에 잘 일치하는 반면 기존 식은 과대 산정하는 경향이 있었다. 제안된 이론식을 통해 수리량이 변화는 경우 2차류가 어떻게 변하는지를 확인해 본 결과, 사행도, 조도, 하폭 대 수심비가 클수록 2차류는 증가하였다. 또한 조도 및 하폭 대 수심비의 변화에 따라 2차류의 흐름방향 분포가 민감하게 반응하였다. In this study, a theoretical equation was derived based on Odgaard (1986) and Chang (1988) to reveal the streamwise variation of the secondary flow in meandering channels. The new equation describes the transverse component of the secondary flow as a function of stream wise and vertical directions. To validate the proposed equation, hydraulic experiments were conducted in laboratory meandering channels having different sinuosity. Comparison of experimental results with the proposed equation and an existing equation revealed that the equation was in good agreement with the measured data. However, the existing equation overestimated the transverse velocity. Investigation of the variation of the secondary flow with respect to hydraulic parameters based on the new equation showed that the secondary flow tended to increase as the sinuosity, the roughness, and the aspect ratio became larger. Also, streamwise profile of the secondary flow was sensitive to variations of the roughness and the aspect ratio.

팔당호 수질사고 예경보 시스템개발에 관한 기초연구

백경오(Baek Kyong Oh),최현근,안성식,좌승희 경기연구원 2008 경기개발연구원 기본연구 Vol.2008 No.11

The accidental water pollution arises from inflow of chemically-polluted water by a fire disaster, a traffic accident, a breakdown of sewage treatment plant, and so on. In Paldang reservoir that is a source of water supply to 23 million people, there is a storing possibility that the accidental water pollution will happen because a pollution source and a water intake facility co-exist in the same region. Thus, to protect water resources from the accidental water pollution, it is necessary to develop a early forecasting and alarm system at Paldang watershed. In this study, historical accidents of the water pollution were reviewed, and cases of the system for forecasting and alarm from the accidental water pollution were searched to employ a proper type to Paldang watershed. Then the numerical model for forecasting water quality, RAMS(river analysis modeling system), was selected, and the behavior of pollutants was calculated based on several scenarios of the accidental water pollution by means of the numerical model. Also managemental plans for situation of the accidental water pollution happening at Paldang watershed were simulated. According to the simulating results, a plan of increase of discharge at Cheongpyeong Dam reduced the peak concentration of pollutants, whereas extended the time for stopping water intake. Another plan, drop of water elevation at Paldang Dam, decreased seriously the time for stopping water intake although there were a little effect to decrease the peak concentration. Thus it was concluded that appropriate combinations of the plans for the increase discharge and the dropping water elevation should be used to deal with the accidental water pollution. The system for forecasting and alarm from the accidental water pollution should have two elements; The system should predict exactly the arrival time and dispersion of harmful substance in Paldang reservoir. The system should show the available results without delay. In order to satisfy these conditions, the system is based on real-time input data giving information about the accident as well as water discharge and water quality, which can be retrieved from the main warning stations via remote transmission from the gauging sites. Also the system should have a early warning module based on UMS(unified messaging system) to spread effectively the situation of the accidental water pollution among the citizens.

수중보 이설 및 변형에 따른 한강 하구 흐름 특성

백경오(Baek Kyong Oh),임동희(Yim Dong Hee) 대한토목학회 2011 대한토목학회논문집 B Vol.31 No.2B

본 연구에서는 한강하구의 흐름에 직접적인 영향을 미치는 구조물인 신곡수중보의 하류 이설 후 변형, 그리고 철거 등을 가정하여 이에 따른 수리특성을 평면 2차원 수치모형을 통해 분석하였다. 2차원적 해석은 보 이설이나 변형이 주변 지형, 특히 습지에 어떤 수리학적 영향을 미치는지 확인할 수 있게 하였다. 모의에 사용된 조위 및 유황은 2007년도 자료를 바탕으로 하였으며, 유량은 풍수기와 평수기로 구분하고 조위는 대조기와 소조기를 포괄하였다. 연구대상 영역으로 한강상류는 한강대교, 임진강상류는 통일대교, 허구경계는 유도로 잡았다. 모의결과 수중보 이설 및 변형에 따라 만조시 해수 유입 영향권이 크게 변화하였으며, 주요 지점의 수위는 유량 및 조위 조건에 따라 변동폭이 다양하게 나타났다. In this study, the flow characteristics of Han River Estuary were investigated by using a two-dimensional numerical model according to the assumption of shift and modification of the Shingok submerged weir. The two-dimensional analysis has contributed to our understanding of the hydraulic effects induced by shift of the weir on the topography, especially wetlands. The tide and flow discharge of 2007 were adopted as an input data for the simulation. The tidal data contained both spring and neap tide, and the flow discharge condition was divided into monsoon and normal seasons. The boundaries of this study were Hangang Bridge, Tongil Bridge, and Yu island. The simulation results showed that influence area of seawater changed depending on the weir shift, and the water level at particular station fluctuated according to the condition of tide and flow discharge.

팔당 유역 수질사고 시나리오에 따른 취수 안전시간 예측

백경오 ( Kyong Oh Baek ) 한국안전학회(구 한국산업안전학회) 2012 한국안전학회지 Vol.27 No.5

In this study, the behavior of pollutant was calculated at Paldang reservior according to several scenarios of the accidental water pollution by means of the numerical models for forecasting water quality. Also managemental plans for situation of the accidental water pollution happening at Paldang watershed were simulated. According to the simulating results, a plan of increase of discharge at Cheongpyeong dam reduced the peak concentration of pollutants, whereas extended the time for stopping water intake. Another plan, drop of water elevation at Paldang dam, decreased seriously the time for stopping water intake although there were a little effect to decrease the peak concentration. Thus it was concluded that appropriate combinations of the plans for the increase discharge and the dropping water elevation should be used to deal with the accidental water pollution at Paldang watershed.

만곡부에서 이론식에 기반한 횡분산계수 경험공식 개발

백경오(Baek, Kyong Oh) 대한토목학회 2012 대한토목학회논문집 B Vol.32 No.6B

본 연구에서는 이론적 배경을 토대로 사행 하천의 만곡부에 적용하기 용이한 횡분산계수 경험공식을 새롭게 제안하였다. 차원해석을 통한 독립변수들의 선정 대신 이론식을 기반으로 독립변수들과 그들의 함수형태를 우선 결정하였다. 결정된 함수식에서 매개변수를 골라내고 이를 고정하는 대신 회귀계수로 전환하여 실제 하천 만곡부에 적합한 경험식을 비선형회귀분석을 통해 제안하였다. 기존의 횡분산계수식들과 비교해 보면 본 연구에서 개발된 식이 관측 분산계수와 대체적으로 일치하는 경향을 보였다. 개발된 식의 특징을 살펴보면 마찰항에 대한 민감도가 상대적으로 적어 조도가 작은 하천에도 적용하기에 무리가 없어 보인다. 또한 개발된 식은 수심 대비 사행반경의 비가 큰 경우에도 기존의 추정식처럼 이상치를 나타낼 우려가 없어 만곡이 심한 사행하천에 적용하기 적합하다. In this study, a new empirical equation for the transverse dispersion coefficient has been developed based on the theoretical background in river bends. The nonlinear least-square method was applied to determine regression coefficients of the equation. The estimated dispersion coefficients derived by the new equation were compared with observed transverse dispersion coefficients acquired from natural rivers and coefficients calculated by the other existing empirical equations. From a comparison of the existing transverse dispersion equations and the new proposed equation, it appears that the behavior of the existing formula in a relative sense is very much dependent on the friction factor and the river geometry. However, the new proposed equation does not vary widely according to variation of friction factor. Also, it was revealed that the equation proposed in this study becomes an asymptotic curve as the curvature effect increases.

미계측 유역에서 저수량 산정 방법 비교 연구

백경오 ( Kyong Oh Baek ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.1

In this study, the methodologies for evaluating the low-flow at the ungauged watershed are reviewed and assessed. The ungauged watershed can be classified into different situations such as the partially recorded watershed and the completely ungauged watershed. The extension method and the percentile method are used to evaluated the low-flow at the partially recorded watershed. The drainage-area ratio method and the regional regression method are used at the completely ungauged watershed. These four methods are applied and validated based on the hydrological and geometric data acquired from unit watersheds in Han River basin for TMDLs. In case of partially recorded watershed, the values of low-flow evaluated by the extension method are in better agreement with measured flow-rate rather than those by the percentile method. In case of completely ungauged watershed, the drainage-area method is broadly used to estimate the low-flow. It must be paid attention to consider the treated sewage discharge produced at watersheds when applying the method