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김철완(C.W. Kim),이융교(Y.G. Lee),이장연(J.Y. Lee) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-
In the present paper, some difficulties encountered in predicting airfoil characteristics are described and solutions for those problems are discussed Since drag is determined by the amounts of pressure and, especially, shear stress, accurate estimation of shear stress is very crucial. However shear stress computation is dependent on the grid density and turbulence model, it should be consistent in preparing grid and turbulence model. When the transition from laminar to turbulent happens at the middle of airfoil, CFD solver should divide the region into laminar and turbulent region based on the transition location.
김철완(Cheol-Wan Kim) 한국항공우주연구원 2007 항공우주기술 Vol.6 No.1
호버링하는 무인기에 대한 지면효과 분석을 위해 여러 고도에 대해 전산해석을 수행하였다. 지면 효과는 무인기 동체 아랫면의 압력을 증가시켜 추가적인 양력을 발생시킨다. 그러나 고도가 로터 직경과 거의 같은 3m에 이르면 지면효과가 거의 소멸되고 3m이상에서는 일정한 크기의 양력을 발생한다. The ground effect on tilt-rotor UAV is analyzed by simulating the hovering UAV for various altitudes. Ground effect increases pressure beneath the UAV body and generates additional lifting force. The ground effect diminishes at altitude 3m and hovering UAV generates constant lifting force above 3m.
김철완(Cheolwan Kim),장병희(Byung Hee Chang),이장연(Jang-Yeon Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The ground effect on tilt-rotor UAV is analyzed by simulating the hovering UAV for various altitudes. Ground effect increases pressure beneath the UAV body and generates additional lifting force. The ground effect diminishes at altitude 3m and hovering UAV generates constant lifting force above 3m.
전산해석을 활용한 두께비 18%익형(Case1)의 공력특성 분석
김철완(Cheolwan Kim),이융교(Yung-gyo Lee) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.3
두께비 18% 익형(KARI-11-180)에 대한 공력특성 분석이 전산해석기법을 활용해 수행되었다. 익형주위의 격자는 벽면에서 수직으로 투영하여 경계층 격자를 형성하였고 익형 후방에는 정밀한 후류 예측을 위해 조밀한 격자를 위치하였다. 원방경계까지의 거리는 익형코드의 100배로 정하였고 익형시험결과와의 비교를 위해 자유류 속도, 익형 코드 및 Reynolds수를 풍동시험과 동일하게 정하였다. 또한 난류 모델은 천이지점 예측이 우수한 transition SST 및 DES 모델을 사용하였다. 3차원 전산해석은 세장비가 2와 5인 익형모델에 대해 수행되었는데 양력은 풍동시험결과보다 높은 값을 항력은 낮은 값을 예측하였다. Aerodynamic analysis for the airfoil, KARI-11-180 having 18% thickness ratio, was performed with CFD techniques. The boundary layer grid was generated by projecting the wall grid normally and fine grid was placed behind the trailing edge to capture the wake accurately. The distance to the far boundary is 100 chords and the flow condition is same as the wind tunnel test condition. Transition SST and DES turbulence models were utilized for accurate prediction of the transiton point. The predicted lift is higher but the drag is predicted lower than the wind tunnel test. 3-dimensional results with airfoil models of which aspect ratio were 2 and 5 were compared with 2-dimensional results.
김철완(C.W. Kim),이융교(Y.G. Lee) 한국전산유체공학회 2008 한국전산유체공학회 학술대회논문집 Vol.2008 No.-
In the present paper, fowler flap was optimized to maximize the lift with response surface method. Leading edge shape and the gap between main airfoil and flap, were optimized and the aerodynamic characteristics was improved considerably. The optimized flap has more rounded leading edge and bigger gap. Before angle of attack, 10°, lift and drag are improved and the optimized flap shows similar aerodynamic characteristics to the original flap. The flow condition for optimization was angle of attack, 10°, Mach number, 0.2, flap deflection, 40°.
김철완(Cheolwan Kim),정진덕(Jindeog Chung) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.10
본 논문에서는 CRW 무인 항공기에 사용되는 타원익형과 전기체의 공력해석 및 동체와 로터를 연결하는 허브주위의 공기역학적 현상에 대한 분석을 수행하였고 허브로 인한 항력 증가를 감소할 수 있는 방안을 모색하였다. 또한 항력 감소를 위해 제안한 fairing 장착방법을 풍동시험을 통해 그 효과를 확인하였다. In this study, CFD analysis for 2D ellipse and 3D CRW UAV are performed. Furthermore, flow analysis around a hub connecting body and rotor is analyzed and a strategy to reduce the drag caused by the hub is sought. Also, the idea of fairing installation is confirmed by a wind tunnel test.
김철완(C. W. Kim) 한국전산유체공학회 2003 한국전산유체공학회지 Vol.8 No.3
A non-dissipative and very accurate one-dimensional upwind leapfrog method is extended to higher-order and multi-dimensional advection and acoustic equations. The higher-order versions are developed by extending the stencils in space and time. The schemes are then successfully applied to the classical test cases for advection and acoustics.