• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.38-44
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• 2000

An oil hydraulic line is modeled in which a pipe or two pipes of different size connected in series and terminated in a chamber, i.e. a composite line system. The frequency response characteristics are investigated analytically and experimentally. The theoretical analysis is base on unsteady laminar flow of a viscous compressible fluid. It is generally difficult to obtain exactly the frequency equation of these lines system and its solutions in consideration of viscosity of hydraulic fluid, because the diameters of two pipes and length are different. The effect of the position where the cross-sectional area of changes suddenly, the inner radius of pipe and the volume of terminal chamber on the frequency characteristics of this composite line system are also described.

• 동력기계공학회지
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• 제2권1호
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• pp.45-51
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• 1998

An analyzing method for pressure fluctuations in oil hydraulic pipe network was developed in this study. The object pipe network has multi-branch configuration, and the pipelines of it are composed of metal tubes and flexible hoses. Transfer matrix method, in other words impedance method, was used for the analysis. Values of physical parameters describing the characteristics of flexible hose were measured by experiments and reflected to the analysing procedure. The reliability and usefulness of the analyzing method were confirmed by investigating computed results and experimental results got in this study.

• 한국수자원학회논문집
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• 제33권3호
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• pp.289-298
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• 2000

본 연구에서는 대구광역시에 위치하고 있는 서변 펌프가압장에서 발생되는 수격압을 최소화하기 위해 사용되는 감압밸브와 공기밸브의 최적 위치결정과 감압밸브의 최적 열림정도를 도모하였다. 가압장에서 발생하는 펌프의 급정지에 기인한 수격현상은 특성선방법을 이용하여 모의를 하였다. 최적화 방법은 강력한 탐색능력을 가지고 있으며 특히 비선형 문제를 해결하는데 탁월한 성능을 가지고 있는 유전자 알고리즘을 이용하여 실시하였다. 유전자 알고리즘의 계산결과는 감압밸브의 열림시간을 적게 할수록 최고 압력수두의 완화에 효과적이고, 열림시간을 크게 할수록 최대부압의 완화에 효과적임을 알 수 있었다. 본 연구는 특성선방법을 기반으로 하는 관망부속물들의 해석이 유전자 알고리즘과 결합되어 관로내 관로부속물의 최적설계에 도움을 줄 수 있음을 보여준다.

• 한국지반환경공학회 논문집
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• 제10권7호
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• pp.117-123
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• 2009

본 연구에서는 흐름에 의한 관로의 세굴특성을 조사하기 위해서 수리모형실험을 실시하였다. 관경 45mm, 60mm, 90mm의 관에 대해서 유속을 0.2m/s에서 0.5m/s까지 변화시켜 가면서 45회의 실험을 실시하였다. 관로 주변에서 세굴의 발달과정을 관찰하였고, 관경과 유속 변화에 따른 평형세굴심을 관찰하였다. 실험결과에 의하면 평형세굴심은 유속과 관경에 비례하는 것으로 나타났다. 관경이 평형세굴심에 미치는 영향이 유속의 영향보다 큰 것으로 나타났다. 상대세굴심과 Reynolds 수, Shields 수, Froude 수 사이의 상관성을 분석하였다. Froude 수와 상대세굴심이 0.900의 높은 결정계수를 갖는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제73권3호
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• pp.339-351
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• 2020

Earthquakes are natural disasters that cause serious social disruptions and economic losses. In particular, they have a significant impact on critical lifeline infrastructure such as urban water transmission networks. Therefore, it is important to predict network performance and provide an alternative that minimizes the damage by considering the factors affecting lifeline structures. This paper proposes a probabilistic reliability approach for post-hazard flow analysis of a water transmission network according to earthquake magnitude, pipeline deterioration, and interdependency between pumping plants and 154 kV substations. The model is composed of the following three phases: (1) generation of input ground motion considering spatial correlation, (2) updating the revised nodal demands, and (3) calculation of available nodal demands. Accordingly, a computer code was developed to perform the hydraulic analysis and numerical modelling of water facilities. For numerical simulation, an actual water transmission network was considered and the epicenter was determined from historical earthquake data. To evaluate the network performance, flow-based performance indicators such as system serviceability, nodal serviceability, and mean normal status rate were introduced. The results from the proposed approach quantitatively show that the water network is significantly affected by not only the magnitude of the earthquake but the interdependency and pipeline deterioration.

• 상하수도학회지
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• 제32권5호
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• pp.411-419
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• 2018

The residual chlorine concentration is an essential factor to secure reliable water quality in the water distribution systems. The chlorine concentration decays along the pipeline system and the main processes of the reaction can be divided into the bulk decay and the wall decay mechanisms. Using EPANET 2.0, it is possible to predict the chlorine decay through bulk decay and wall decay based on the pipeline geometry and the hydraulic analysis of the water distribution system. In this study, we tried to verify the predictability of EPANET 2.0 using data collected from experimental practices. We performed chlorine concentration measurement according to various Reynolds numbers in a pilot-scale water distribution system. The chlorine concentration was predicted using both bulk decay model and wall decay model. As a result of the comparison between experimental data and simulated data, the performance of the limited $1^{st}$-order model was found to the best in the bulk decay model. The wall decay model simulated the initial decay well, but the overall chlorine decay cannot be properly predicted. Simulation also indicated that as the Reynolds number increased, the impact of the wall.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2009년도 춘계학술발표회
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• pp.177-178
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• 2009

관로내의 유속이 급격히 변하면 압력도 크게 상승하거나 강하하게 되어 유체 과도현상을 일으키게 된다. 이러한 수격현상에 대한 연구는 펌프스테이션이 커지고 유체를 이송하는 시스템이 대형화되어 그 중요성이 더욱 증가하였다. 이것은 파이프라인이 길어지고 복잡해지기 때문이다. 이 연구에서는 특성법을 이용하여 대형펌프 시스템의 밸브 개폐로 발생하는 수격현상을 평가하였다.

• 한국유체기계학회 논문집
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• 제8권5호
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• pp.22-28
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• 2005

As the water supply facilities are recently getting larger, the domestic waterworks become multi-regional water supply system. Large water supply facilities generally consist of the intake pumping station, water treatment plant and water supply/distribution facilities. Although the pumping stations and the pipeline systems are used to pump up water, it often happens pipeline damage and flooding accident by the water hammer. In this paper, the intake pumping station is guaranteed by both the computer simulation and the field test analysis. This study is contributed to the safe operation program for the pumping station in which results of the adjustment on the safety plan of the pumping station, the air valve and the valve closing time.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.199-207
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• 2004

Water supply facilities are recently getting larger according as domestic waterworks become multi regional water supply system. Large water supply facilities generally consist of the intake pumping station, water treatment station and water supply & distribution facilities. Although pumping stations and pipeline systems are used to pump up water, it often happens pipeline damage and flooding accident by the water hammer. As a result of this study, a pumping station is guaranteed by the computer simulation and field test analysis. Therefore these are contributed safety operation in pumping station through adjustment of the pumping station safety plan, air valve and valve closing time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.305-308
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• 1996

An analyzing method for pressure fluctuation in oil hydraulic pipe network was developed in this study. The object pipe network has multi-branch configuration, and the pipeline of it is composed of steel tubes, flexible hoses. Also, accumulators, orifices and lumped oil volume components are attached on it. Transfer matrix method, in other words impedance method, was used for the analysis. The reliablity and usefulness of the analyzing method was confirmed by comparing and investigating computed results and experimental results got in this study.