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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.
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.
적응 격자계를 이용한 초음속 난류유동장의 측면제트분사에 대한 수치적연구
김종록(J.R. Kim),김익태(I.T. Kim),김재수(J.S. Kim) 한국전산유체공학회 2001 한국전산유체공학회지 Vol.6 No.2
Two-dimensional steady flowfields generated by slot injection into supersonic flow are numerically simulated by the integration of Navier-stokes equation with two-equation k-turbulence model. High-order upwind scheme is used on unstructured adaptive meshes. The numerical results are compared with experimental data in terms of surface static pressure distributions, the length of the upstream separation region, and the height of the Mach surface for steady flowfields with a Mach number of 3.71 and a unit Reynolds number of 5.83×10^6/m.
역류제트를 이용한 센터바디 디퓨져의 열차폐 특성에 관한 연구
김종록(J.R. Kim),이경환(K.H. Lee),김재수(J.S. Kim) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.2
In the development of liquid-propellant rocket engines, it is important to simulate high-altitude environments and verify the performance of the engines in these environments. Supersonic diffusers are the most important technology in high-altitude simulation facilities. Using the thermal protection system based on the counter-flow jet, as proposed in this study, the cooling efficiency of the CBD(center-body diffusers) can realize an efficient high-altitude simulation facility for the liquid-propellant rocket engine. The analysis for the supersonic flow with a counter-flow jet was performed by experimental and numerical methods. The thermal protection effect by the counter-flow jet in the center body diffuser was analyzed by a numerical method. When the pressure ratio of counter-flow jet injection is less than 0.5, the cooling effect is insignificant, but when the pressure ratio is 1.0 or more, the cooling effect is more than 1000K.
초음속난류유동장에서 후향계단 후류의 측면제트분사에 대한 수치적연구
김종록(J.R. Kim),김재수(J.S. Kim) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
This paper describes numerical research on transverse jet behind rearward-facing step in turbulent supersonic flowfields without chemical reaction. The purpose of transverse jet behind rearward-facing step is to improve mixing of the fuel in the combustor. Two-dimensional unsteady flowfields generated by slot injection into supersonic flow are numerically simulated by integration of Navier-Stokes equation. Final-scale turbulence effects are modeled with two-equation k- E model. Numerical methods are modeled high-order upwind TVDschemes. A total of 4 cases are computed, comprising slot momentum flux ratios at four step heights downstream of the step. These numerical results are represented periodic phenomenon in unsteady flowfields.