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권혁빈(Kwon Hyeok-Bin),이관중(Yee Kwan-Jung),이동호(Lee Dong-Ho) 한국철도학회 2000 한국철도학회 학술발표대회논문집 Vol.- No.-
The tunnel booming noise generated by a train moving into a tunnel has been one of the most serious constraints in the development of the high-speed trains. It is well known that the nose shape of the train has the significant influence on the intensity of the booming noise. In this study, the nose shape has been optimized by using the response surface methodology and the axi-symmetric compressible Euler equations. The parametric studies are also performed with respect to the slenderness ratio, the blockage ratio and the train speed to investigate their sensitivities to the optimization results. The results show that it is possible to define more general design space by introducing the Hicks-Henne shape functions, resulting in the more effective nose shape than that of Maeda. The mechanism and the aspects of the train-tunnel interaction were also investigated from the results of the parametric study.
유체-구조 연계해석을 통한 소형민수헬기(LCH) 공력 및 구조하중 해석
이다운(Da-Woon Lee),김기로(Kiro Kim),이관중(Kwan-Jung Yee),정성남(Sung-Nam Jung) 한국항공우주학회 2019 韓國航空宇宙學會誌 Vol.47 No.7
본 연구에서는 국내 개발 중인 소형 민수 헬리콥터(LCH)에 대해 유체-구조 연계 기법을 이용하여 로터 공력 및 구조 하중에 대한 고정밀 공탄성 해석을 수행하였다. LCH 로터는 일반적인 힌지형 로터와 달리 탄성체 베어링과 블레이드 상호 연계형 댐퍼 시스템을 탑재하였으며, 이에 대한 구조동역학 해석을 위해 CAMRAD-II 모델을 구축하였다. 주 운용조건인 전진비 0.28 순항조건에서 단일 로터 모델과 로터-동체 모델에 대한 유체-구조 연계해석을 수행하여 동체 모델링의 효과를 분석하였다. 동체 모델링이 로터의 하중 및 블레이드-와류 간섭에 미치는 영향은 제한적이지만, 루트에서 발생한 와류가 동체 효과에 의해 꼬리 로터에 무시할 수 없는 영향을 줄 수 있음을 수치적으로 확인하였다. 양력선 이론 기반의 구조동역학 해석 결과는 유체-구조 연계해석 결과와 대체로 부합하는 결과를 보였으나, 비정상 유동 예측 모델의 한계로 인해 공력 하중, 탄성 변위에 대한 peak-to-peak 크기를 낮게 예측하고 구조 진동 하중에서 주요한 위상 차이를 나타냈다. The airloads and structural loads of Light Civil Helicopter (LCH) rotor are investigated using a loose CFD/CSD coupling. The structural dynamics model for LCH 5-bladed rotor cwith elastomeric bearing and inter-bladed damper is constructed using CAMRAD-II. Either isolated rotor or rotor-fuselage model is used to identify the effect of the fuselage on the aeromechanics behavior at a cruise speed of 0.28. The fuselage effect is shown to be marginal on the aeromechanics predictions of LCH rotor, though the effect can be non-negligible for the tail structure due to the prevailing root vortices strengthened by the fuselage upwash. A lifting-line based comprehensive analysis is also conducted to verify the CFD/CSD coupled analysis. The comparison study shows that the comprehensive analysis predictions are generally in good agreements with CFD/CSD coupled results. However, the predicted comprehensive analysis results underestimate peak-to-peak values of blade section airloads and elastic motions due to the limitation of unsteady aerodynamic predictions. Particularly, significant discrepancies appear in the structural loads with apparent phase differences.
Aerodynamic Shape Design of Rotor Airfoils Undergoing Unsteady Motion
Yee, Kwan-Jung,Kim, You-Shin,Lee, Dong-Ho 서울대학교 항공우주신기술연구소 2001 항공우주신기술연구소 연구보고 Vol.2 No.1
The objective of the present study is to suggest a new design method that can handle dynamic response of an airfoil undergoing unsteady motion and flow condition. To achieve this goal, a new objective function and constraints are defined to represent overall characteristics over a single cycle and a weighting function is also introduced to enable a designer to determine specific design point. Response surface methodology is exclusively employed to construct and optimize the response surface models of objective functions and constraints. The advantages of the present method have been demonstrated by the comprehensive comparison with the static 3-point design method. It is found that the present method can yield a better design result due to the following reasons: (1) the static performance is not always proportional to the dynamic performance; (2) the moment constraint used in 3-point design is too tight to allow enough variations of design variables; (3) the objective function of 3-point design may be implicitly overweighted at a certain control point so that overall aerodynamic performance is miscalculated unlike in the present method. The variations of aerodynamic performance with weighting functions are also discussed.