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RISS 인기검색어
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- 저자 : 김재수(J. S. Kim) (검색결과 71 건)
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조성일,변기훈,변성훈,김재수,Cho, Seong-il,Byun, Gihoon,Byun, Sung-Hoon,Kim, J.S. 한국음향학회 2018 한국음향학회지 Vol.37 No.4
This paper presents an algorithm for passive localization of a ship by applying the ray back-propagation technique to the ship radiation noise data. The previous method [S. H. Abadi, D. Rouseff and D. R. Dowling, J. Acoust. Soc. Am. 131, 2599-2610 (2012)] estimates the position of a sound source in the near-field environment with no array tilt by using the RBD (Ray-based Blind Deconvolution) and ray back-propagation techniques. However, when there exists an array tilt, the above method leads to a large position estimation error. In order to overcome the problem, this study proposes an algorithm that estimates the position of a sound source by correcting the array tilt using the RBD and ray back-propagation techniques. The proposed algorithm was verified by using the ship noise of SAVEX15 (Shallow-water Acoustic Variability EXperiment in 2015) experimental data.
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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.
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고해상도 수치기법의 경계조건에 따른 공력음향 특성에 관한 연구
이상수(S.S. Lee),김재수(J.S. Kim) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.3
The present paper focuses on the analysis of aero-acoustics characteristic by appling different four boundary conditions. The high-order and high-resolution numerical schemes are used for discrete accurate computation of compressible flow. The four boundary conditions include extrapolation, characteristic boundary condition, zonal characteristic boundary condition. These boundary conditions are applied to the computation of two dimensional circular cylinder flows with Mach number of 0.3 and Reynolds number of 400. The computation results are validated against measurement data and other computation results for the Strouhal frequency of vortex shedding, the mean drag coefficient and root-mean-square lift for the unsteady periodic flow regime. The characteristics of secondary frequency is predicted by three kinds of boundary conditions.
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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.
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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.
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