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변영환,안태용,장안식 건국대학교 1997 學術誌 Vol.41 No.2
극초음속 유동현상은 많은 난제를 안고 있으며, 컴퓨터의 발달에 힘입어 공기역학의 많은 분야에서 전산유체역학(CFD)이 널리 쓰이고 있으나 개발된 코드의 검증 등에서 여전히 실험의 뒷받침이 필요한 상황이다. 국내에서의 극초음속 실험연구가 새로이 시작되는 단계에서 실험장치에 대한 수요가 높아지고 있으며 따라서 그 설계, 제작 및 운용에 대한 지식과 경험의 축적이 절실하다 하겠다. 본 연구에서는 교육용 실험장치로서의 단순 충격파관을 설계, 제작하여 그 검증을 수행하였다. To study hypersonics like external flow field over a re-entrying spacecraft, there are lots of phenomena to consider. Although recent movement to Computational Fluid Dynamics(CFD) in most aerodynamics fields, experiments still have strong aspect which is not easily ignored. Also a newly generated CFD code should be validated to be applied, it needs experimental data. Shock tube in hypersonics is not a new technology, but there is almost nothing in designing, development , and operation of hypersonic test facility In Korea. In this study, a simple shock tube was designed, manufactured, and tested its characteristics. An important result of this study is the experience of development of shock tube, and it would be helpful to design a new facility or to improve existing one.
변영환 建國大學校 附設 産業技術硏究所 1993 논문집 Vol.18 No.-
Numerical simulation of the hypersonic viscous flow over a two dimensional circular cylinder in shock tunnel has been attempted by using MacCormack's explicit time dependent predictor-corrector finite-difference method. The problem consists of two parts which ar a quasi-one dimensional nozzle flow for a convergent-divergent nozzle section and a flow over a circular cylinder for an aerodynamic model. The time dependent solution of the former has been used a the in-flow boundary condition for the latter problem, whose governing equations are two dimensional full Navier-Stokes equations. For a nozzle flow, the start-up process of the shock tunnel and the time required to the steady state have been studied. For a flow over a cylinder, the transients at early time and the effects of the artificial damping terms have been studied.
변영환,허철준 건국대학교 산업기술연구원 1997 건국기술연구논문지 Vol.22 No.-
There are shock tunnel, gun tunnel, piston tunnel and expansion tube as ground-based hypersonic test facilities. Performances of these facilities depend on many things, but mainly characteristics of driver. These drivers are very important impulse facilities but hardly known for lack of theoretical analysis. Most of knowledges about drivers are based on facility developer's own experiences and experimental data. Characteristics of shock wave compression and piston compression have been studied in this reseach to study characteries of drivers of impulse test facilities. Change of ratio of driver pressure to stagnation pressure has been compared to well known results of other researches and it shows very similar trend. Shock wave compression is more effective than piston compression in low pressure, but piston compression is more effective than shock wave compression in high pressure. Results of our gas gun tests show that piston compression is more effective to get higher stagnation pressure in the region of the above 72 of driver pressue ratio.
항공기 개념설계를 위한 천음속 영역의 공력특성 예측에 관한 연구
전권수,김상진,이재우,변영환 건국대학교 산업기술연구원 2000 건국기술연구논문지 Vol.25 No.-
During the aircraft conceptual design phase, rapid aerodynamic analyses over various configurations are required. Hence, empirical and analytic techniques play important roles in estimating the aerodynamic characteristics. In this study, the aerodynamic characteristic estimation technique for transonic region based on empirical and analytical is developed. By comparing with the results of the wind tunnel experiment and existing prediction method, it is verified that the present method is accurate and useful.
변영환(Yung Hwan Byun),배기준(Ki Joon Bae),J. A. Schetz,이재우(Jae-Woo Lee) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.4
초음속 유동하에서 측 추력기의 후방에 램프를 설치하였을 경우의 유동 현상을 실험 및 수치해석을 이용하여 해석하였다. 실험적인 방법으로, 가시화방법으로는 쉴리렌, 압력 측정을 위한 방법으로 압력 탭(Pressure Tap), Pressure Sensitive Paint를 이용하였으며, 수치해석을 위하여 AeroSoft사의 GASP ver. 4.0을 사용하였다. 실험조건은 자유류의 흐름이 마하수 4 측 추력기와 자유류의 압력비가 532이었으며 GASP을 사용하여 3D 램프형상에 대한 고찰을 하였다. 위의 모든 결과들은 후방의 램프가 없을 경우와 비교를 통하여 램프를 장착하였을 경우 수직력의 감소없이 피칭다운 모멘트가 70%정도 감소함을 확인하였다. An experimental and computational study has been performed for investigation of the jet interaction in supersonic flow with a ramp located behind a sonic, lateral jet. The experimental techniques include schlieren, pressure taps, and Pressure Sensitive Paint. The numerical solver used in this study is AeroSoft’s structured flow solver GASP Version 4.0. A Mach 4 crossflow with a pressure ratio of 532, and the 3D ramp was designed by parametric study using GASP. The results showed that the ramp located downstream of the jet decrese the nose-down pitching moment by 70% without a force loss.
변영환 건국대학교 산업기술연구원 2005 건국기술연구논문지 Vol.30 No.-
This article reports the activities at the 21st International Congress of Theoretical and Applied Mechanics held in Warsaw, Poland, 15-21 August 2004. This conference features sessions on various fields of research regarding solid and fluid mechanics with analytical, numerical, and experimental methods.
AIAA Applied Aerodynamics Conference 참가기 : 미국 플로리다주 올랜도를 다녀와서
변영환 건국대학교 산업기술연구원 2004 건국기술연구논문지 Vol.29 No.-
This article reports the activities at the 21st AIAA Applied Aerodynamics Conference held in Orlando, Florida, 23-26 June 2003. This conference features sessions on research, design, development, and verification in the diverse fields of aerodynamics, with a focus on technology applications.