• 상하수도학회지
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• 제22권6호
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• pp.657-664
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• 2008

This research compared several unsteady friction models for transient analysis of pipeline system. Unsteady friction is an important factor for accurate simulation of hydraulic transient. Steady friction, quasi-steady friction, Zielke's model and two versions of Brunone model were compared with measurement data of identical pipeline conditions. This study showed that the existing simple steady friction model can be useful for the safer design of pipeline system due to its overestimation of waterhammer, but introduction of more elaborate models are required for advanced analysis such as inverse transient analysis of friction or leakage and the preliminary analysis of water quality prediction of water distribution system.

• 상하수도학회지
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• 제20권2호
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• pp.207-214
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• 2006

The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient method. In order to obtain essential data for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system, Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors gives reasonable match between the computed and measured results on the condition of the flow situations presented in the paper. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1395-1399
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• 2006

The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient analysis. In order to obtain pressure variation for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system. Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors, reasonable match between the computed and measured pressure were presented on the condition of the flow situations. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.92-99
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• 1998

Unsteady flow problems created by hydraulic transients in pipeline systems with pump are of significant importance because they can cause excessive pressure, cavitation, vibration and noise. In this paper, an analysis of transient flow for the pump pipelines is developed by means of the characteristic method. The calculated results of the program to simulate water hammer due to sudden valve closure in a simple pipeline are compared with those of the analytical method. Expecially the water hammer due to power failure in pump pipeline system with surge tank was simulated. As the results, both the upsurge and the downsurge along the pipeline are reduced.

• 대한환경공학회지
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• 제27권10호
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• pp.1065-1071
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• 2005

유체의 파속과 파형을 이용한 많은 누수탐지 기술들이 연구되고 있다. 본 연구에서는 파속을 계산하기 위해 천이류 방법을 이용하였고 누수지점의 탐지를 위해 주파수 분석방법을 개발하였다. 가압관망의 자료획득 시스템을 개발하였으며, 이를 통해 고주파 수압자료를 획득하였다. 이들 방법론은 측정과 모의 과정에서 발생되는 오차로 인한 불화실성을 적절히 처리할 수 있으며, 수압자료의 측정간을 근거로 누수의 예측지점을 추정할 수 있다. 본 연구에서 개발된 방법은 수압자료로부터 확보되는 정보를 기반으로, 누수가 동반된 천이현상에서 누수예측능력을 보여주고 있다.

• 상하수도학회지
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• 제37권6호
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• pp.437-446
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• 2023

We propose a transient evaluation scheme using a pressure measurement in a complicate pipeline systems. Conservation of mass and momentum equations in time domain can be transformed into a pressure head and flowrate relationship between upstream and downstream point in frequency domain. The impedance formulations were derived to address measured pressure at downstream to evaluate of flowrate or pressure head at any point of system. Both branched pipeline element and looped pipeline element can be generally addressed in the platform of the basic reservoir pipeline valve system. The convolution of time domain response function with measured pressure head from a downstream point provides flowrate or pressure head response in any point of the designated pipeline system. The proposed method was validated through comparison between traditional method of characteristics and the proposed method in several hypothetical systems.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1334-1339
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a forced vibration analysis. The dynamic behavior of the buried pipelines for the forced vibration is found to exhibit two different forms, a transient response and a steady state response, depending on the time before and after the transfer of a seismic wave on the end of the buried pipeline. The former is identified by a slight change in its behavior before the sinusoidal-shaped seismic wave travels along the whole length of the pipeline whereas the latter by the complete form of a sinusoidal wave when the wave travels throughout the pipeline. The transient response becomes insignificant as the wave speed increases. From the results of the dynamic responses at the many points of the pipeline, we have found that the responses appeared to be dependent critically on the boundary end conditions. Such effects are found to be most prominent especially for the maximum values of the displacement and the strain and its position.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.426-434
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• 2006

The impact of leakage was incorporated into the transfer functions of the complex head and discharge. The impedance transfer functions for the various leaking pipeline systems were also derived. Hydraulic transients could be efficiently analyzed by the developed method. The simulation of normalized pressure variation using the method of characteristics and the impulse response method shows good agreement to the condition of turbulent flow. The leak calibration could be performed by incorporation of the impulse response method with Genetic Algorithm (GA) and Harmony Search (HS). The objective functions for the leakage detection can be made using the pressure-head response at the valve, or the pressure-head or the flow response at a certain point of the pipeline located upstream from the valve. The proposed method is not constrained by the Courant number to control the numerical dissipation of the method of characteristics. The limitations associated with the discreteness of the pipeline system in the inverse transient analysis can be neglected in the proposed method.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.269-277
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• 2009

The current paper focuses on the analysis of transient cavitating flow in pressurised polyethylene pipes, which are characterized by viscoelastic rheological behaviour. A hydraulic transient solver that describes fluid transients in plastic pipes has been developed. This solver incorporates the description of dynamic effects related to the energy dissipation (unsteady friction), the rheological mechanical behaviour of the viscoelastic pipe and the cavitating pipe flow. The Discrete Vapour Cavity Model (DVCM) and the Discrete Gas Cavity Model (DGCM) have been used to describe transient cavitating flow. Such models assume that discrete air cavities are formed in fixed sections of the pipeline and consider a constant wave speed in pipe reaches between these cavities. The cavity dimension (and pressure) is allowed to grow and collapse according to the mass conservation principle. An extensive experimental programme has been carried out in an experimental set-up composed of high-density polyethylene (HDPE) pipes, assembled at Instituto Superior T$\acute{e}$cnico of Lisbon, Portugal. The experimental facility is composed of a single pipeline with a total length of 203 m and inner diameter of 44 mm. The creep function of HDPE pipes was determined by using an inverse model based on transient pressure data collected during experimental runs without cavitating flow. Transient tests were carried out by the fast closure of the ball valves located at downstream end of the pipeline for the non-cavitating flow and at upstream for the cavitating flow. Once the rheological behaviour of HDPE pipes were known, computational simulations have been run in order to describe the hydraulic behaviour of the system for the cavitating pipe flow. The calibrated transient solver is capable of accurately describing the attenuation, dispersion and shape of observed transient pressures. The effects related to the viscoelasticity of HDPE pipes and to the occurrence of vapour pressures during the transient event are discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제12권4호
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• pp.46-52
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• 1988

The cavitation inception in oil hydraulic pipeline was investigated experimentally and numerically. In the experiment, negative pressures below-1 MPa(absolute pressure) were measured, associated with the transient flows in oil hydraulic pipeline. These experimental results show that the common hydraulic oil in the experimental pipeline withstands large tensions. In order to interpret the experimental results on cavitation inception, the growth of a spherical bubble in viscous compressible fluid due to a stepwise pressure drop was investigated by numerical analysis, and the critical bubble radius was obtained. The calculated value of the critical bubble radius corresponding to the negative pressure measured in the experiment is so small that the premised conditions about the bubble shape in the analysis is unsatisfactory. The physical significance of this calculated result implies the fact that there hardly exist free bubbles which can act as cavitation nuclei in the experimental pipeline.