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허지성,김현준,송용석,김상현 대한상하수도학회 2016 상하수도학회지 Vol.30 No.5
Method of characteristic(MOC) has been widely used as a transient analysis technique for pressurized pipeline systems. There are substantial studies using MOC for the water hammer triggered through instantaneous valve closures, pump stoppage and pump startup for pipelines systems equipped with a centrifugal pump. Considering restrictions of MOC associated with courant number condition for complicated pipeline systems, an impulse response method(IRM) was developed in the frequency domain. this study implements the impact of centrifugal pump using transfer function in frequency domain approach. Using pump performance curve and the affinity law, this study formulated transfer functions which relate complex pressure head at upstream of pump system to that of downstream location. Simulations of simple reservoir-pump-valve system using IRM with formulated transfer function were similar to those obtained through MOC.
EFDC 모형을 이용한 댐 붕괴류 수치모의 및 매개변수 민감도 분석
장철 ( Chul Jang ),송창근 ( Chang Geun Song ) 한국안전학회(구 한국산업안전학회) 2016 한국안전학회지 Vol.31 No.4
In this study, a series of numerical simulation of dam break flow was conducted using EFDC model, and input conditions including cell size, time step, and turbulent eddy viscosity were considered to analyze parameter sensitivity. In case of coarse mesh layout, the propagated length of the shock wave front was △χ longer than that of other mesh layouts, and the velocity results showed jagged edge, which can be cured by applying fine grid mesh. Turbulent eddy viscosity influenced magnitude of the maximum velocity passing through gate up to 20% and the cell Peclet number less than 2.0 ensured no numerical oscillations.
벨마우스의 깊이가 다른 3차원 나선형 축류홴의 최대유량역에서 난류유동장 특성에 대한 대규모와 모사
김장권,오석형 한국동력기계공학회 2019 동력시스템공학회지 Vol.23 No.2
벨마우스 깊이가 다른 3차원 나선형 축류홴(HAF)의 최대 유량에서 난류 유동장의 특성을 분석하기 위해서 대규모와모사(LES)가 수행되었다. HAF의 최대 유량은 기존 축류홴의 절반 정도이다. 최대 유량을 얻기 위한 나선형 임펠러와 벨 마우스 사이에는 최적의 배치조건이 존재하지만, 2피치 나선형 임펠러는 벨마우스의 위치에 관계없이 유량에는 거의 변화가 없다. HAF의 하류에서는 축방향 유동이 관측 된 후, 방사상으로 확산된 유동이 관찰된다. 특히 이 흐름은 챔버 벽의 영향을 받아 와류쌍을 만든다. HAF의 하류에서 생성된 와도 크기는 주로 나선형 날개 팁과 허브 측에서 형성된다.
날개의 스윕과 레이크각의 변화에 따른 튜브 축류홴의 공력성능 평가
김장권,오석형 한국동력기계공학회 2023 동력시스템공학회지 Vol.27 No.5
In this study, a 3D tube axial fan model designed based on the assumption of the total pressure ratio of blade span length was analyzed using large eddy simulation in an incompressible state by changing the sweep and rake angles. As a result, the maximum flowrate increases as the sweep and rake angles increase; however, the maximum static pressure decreases. In addition, the slope of the static pressure performance curve of the tube axial fan, which reflects the sweep and rake around the design flow rate of 1.35m3/min, is not more curved than otherwise, expanding the limit of stall. In addition, after the flow rate is 0.7m3/min, the static pressure and the static pressure efficiency are greatly improved with application of sweep and rake are applied. The highest static pressure efficiency appears at a further increased flowrate as the sweep and rake angles increase. In conclusion, considering the performance of static pressure and static pressure efficiency, it is judged that the tube axial fan with a sweep and rake angle of 20° is the best.