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문지수(J.S. Moon),김재수(J.S. Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Oscillating airfoil have been challenged for the dynamic stalls of airfoil and wind turbines at high angle of attach. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed for the oscillating airfoil at high angle of attack around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.2 and Reynolds number of 1.2×10⁴. The lift, drag pressure distribution, etc. are analyzed according to the pitching oscillation. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.
고해상도 수치 기법을 이용한 횡방향 진동 원형 실린더 주위의 유동해석
문지수(J. S. Moon),김재수(J. S. Kim) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
It was analyzed relation between the transversely oscillation frequency of circular cylinder and the vortex shedding frequency. Thw two dimensional unsteady compressible Navier-Stokes equation was calculated by OHOC(Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynods number of 1000. When the forced frequencies are near the natural Strouhal number of the wakes around a stationary circular cylinder, the history of the lift and drag coefficients has the characteristics of lock-on phenomenon, which means that the coefficients have one primary frequency and are amplified by th forced oscillation. In the non lock-on region, the coefficients have one primary frequency and another resonance frequency by the forced oscillation.
고속열차 대차 측면 페어링 적용을 통한 공기저항 저감 연구
문지수(J.S. Moon),김석원(S.W. Kim),권혁빈(H.B. Kwon) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.1
The aerodynamic drag of high-speed train has been calculated and the effect of bogie side fairing on the aerodynamic drag has been investigated. Computational Fluid Dynamics (CFD) simulation based on steady-state 3 dimensional Navier-Stokes equation has been conducted employing FLUENT 12 and the aerodynamic model of HEMU-430x, the Korean next generation high-speed train under development has been built using GAMBIT 2.4.6. Three types of bogie side fairing configuration, the proto-type without fairing, half-covered fairing to avoid the interference with the bogie frame and full-covered fairing have been adopted to the train model to compare the drag reduction effects of the bogie side fairing configurations and the numerical results yields that the bogie side fairing can reduce the aerodynamic drag of the 6-car trainset up to 7.8%. The aerodynamic drag coefficient of each vehicle as well as the flow structures around the bogie system have also been examined to analyze the reason and mechanism of the drag reduction by bogie side fairing.