• Journal of Korea Water Resources Association
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• v.33 no.S1
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• pp.835-841
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• 2000

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.177-177
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2004.05a
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• pp.91.2-91.2
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• 2004

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.427-438
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• 2001

A numerical model to analyze the unsteady flow in water distribution system was developed by using wave adjustment method. When analyzing the unsteady flow in the real water distribution system, the computational procedures are very complex due to the various boundary condition. Wave adjustment method, which can solve the boundary condition more simply and accurately, was introduced to overcome this difficulty and related equations to solve external flow directly were presented. Using these equations, the numerical model was developed to analyze water hammer. The suggested model was applied to a hypothetical distribution system and a real system with 26 pipes with various external flow boundary condition to evaluate the applicability of the developed model. The simulation results by this model agree with those by Karney's analysis in terms of discharge and pressure.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.131.2-131
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• 2001

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.82-82
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• 2003

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.455-464
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• 2012

In this study, a combined unsteady friction model has been developed to simulate the waterhammer phenomenon for the pipeline system. The method of characteristics has been employed as the modeling platform for the integration of the acceleration based model and the frequency dependant model for unsteady friction. Both Zielke's model and Ramos model were also compared with pressure measurements of a pilot plant pipeline system. In order to validate the modeling approach, a pipeline system equipped with the high frequency pressure data acquisition system was fabricated. The time series of pressure, introduced by a sudden valve closure, were obtained for two Reynolds numbers. A trial and error method was used to calibrate parameters for unsteady friction model. The comparison between different unsteady friction contributions in pressure variation provided the comprehensive understanding in the pressure damping mechanism of waterhammer. The proper evaluation of unsteady friction impact is a critical factor for accurate simulation of hydraulic transient.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.313-317
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• 2009

The orifice in the propellent feeding pipe line of a Liquid Rocket Engine(LRE) is used to balance the pressure of the pipe line. When a LRE starts up, pressure at the upstream of the orifice rapidly increases. In this case, pressure waves occuring by resistance of the orifice may induce low frequency instability in the pipe line. For this reason the study of dynamic characteristics of orifices is needed to prevent the instability. A pump is used to build up the pressure, and the pressure is measured upstream and downstream of the orifice when the orifice diameter is changed. With the increase of orifice diameter, water hammer decreases, but the effect of resistance downstream is increases.

• The KSFM Journal of Fluid Machinery
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• v.3 no.4 s.9
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• pp.52-58
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• 2000

The numerical study on the waterhammer was carried out for the intake pumping station of the metropolitan water supply 6th stage project. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully investigated. The surge tank and the stand pipes effectively protected the tunnels md the downstream region of pipeline from the pressure surge. In case the moment of inertia of the pump and motor was above $5080\;kg{\cdot}m^2$, the column separation did not occur in the pipeline between the pumping station and the inlet of 1st tunnel. As the moment of inertia increased, the pressure surges decreased in the pipeline conveying raw water. The pump control valve was chosen as the main surge suppression device for the intake pumping station. After power failure, the valve disc should be rapidly closed in 2.5 seconds and controlled the final closure to 15 seconds by the oil dashpot. If the slamming happened to the pump control valve, there was some danger of this system damaging. As the reverse flow through the valve increased, the upsurge extremely increased.

• The KSFM Journal of Fluid Machinery
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• v.4 no.4 s.13
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• pp.16-21
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• 2001

The field tests on the waterhammer were carried out for PalDang intake pumping station of the metropolitan water supply 5th stage project. The pumping station was equipped with the pump control valve as the main surge suppression device and the surge relief valve as auxiliary. However, the pump control valve had not been early controlled in the planned closing mode, and the slamming occurred to the valve which abruptly closed during the large reverse flow. Because the pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the shaft of the valve was damaged. It was desirable that the surge relief valve was installed in the pumping station or near the pump exit for the delay of response. After reforming the oil dashpot of the pump control valve, the sliming disappeared and the measured pressure was in fairly good agreement with the results of simulation. In case of three pumps for ${\phi}2,600$ pipeline being simultaneously tripped, the pressure head in the pumping station increased to 95.6 m, and the upsurge caused by the emergency stop of four pumps for ${\phi}2,800$ pipeline was 89.6m. We concluded that the pumping station acquired the safety and reliability for the pressure surge.