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γ-Re<SUB>θ</SUB>천이 모델을 사용한 KARI-11-180 익형의 천이 유동해석
사정환(Jeong Hwan Sa),김기로(Kiro Kim),조금원(Kum Won Cho),박수형(Soo Hyung Park) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.3
본 연구에서는 KFLOW에서 사용하고 있는 γ-Re<SUB>θ</SUB> 천이 모델을 사용하여 KARI-11-180 익형의 공력특성을 수치적으로 예측하고 그 결과를 실험 결과 및 XFOIL과 MSES의 결과와 비교하였다. 완전 난류모델은 천이모델에 비해 마찰항력을 크게 예측하기 때문에 전체적으로 높은 항력을 예측하는 등 천이모델과 완전 난류모델간의 차이를 확인하였다. KFLOW의 γ-Re<SUB>θ</SUB> 모델을 사용한 결과는 실험을 통해 확인된 천이 유동 실험 결과의 특성을 잘 예측하고 있었으며 XFoil이나 MSES의 결과와도 잘 일치하고 있음을 확인하였다. 본 연구를 통해 drag-bucket현상이 익형 표면의 천이점의 급격한 변화로 인해 발생함을 확인하였다. In this study, numerical simulations were performed using the γ-Re<SUB>θ</SUB> transition model of KFLOW for the transitional flow over the KARI-11-180 airfoil. Numerical results of KFLOW were compared with experimental data and two other numerical results of XFoil and MSES. Fully turbulence model was predicted high skin friction drag than transition model because fully turbulence model could not solve the transitional flow. Numerical predictions using the γ-Re<SUB>θ</SUB> model of KFLOW show a good agreement with experimental data and other numerical results. Present numerical results were confirmed the state of drag bucket due to dramatic changing of the transition location on the airfoil surface.
사정환(J.H. Sa),박수형(S.H. Park),김창주(C.-J. Kim),윤철용(C.Y. Yun),김승호(S.-H. Kim),김상호(S. Kim),유영훈(Y.H. Yu) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.2
Numerical optimization of rotor blade airfoils is performed with a response surface method for helicopter rotor. For the baseline airfoils. OA 312, OA 309, and OA 407 airfoils are selected and optimized to improve aerodynamic performance. Aerodynamic coefficients required for the response surface method are obtained by using Navier-Stokes solver with k-w Shear Stress Transport turbulence model. An optimized airfoil has increased drag divergence Mach number. The present design optimization method can generate an optimized airfoil with multiple design constraints, whenever it is designed from different baseline airfoils at the same design condition.
사정환(J.H. Sa),박수형(S.H. Park),김창주(C.J. Kim),윤철용(C.Y. Yun),김승호(S.H. Kim),김상호(S.H. Kim),이재우(J.W. Lee) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
Optimization with metamodel is one of numerical optimization methods. Response surface method is performed for making metamodel. The Hcks-Henne function is used for designing 2D shape of the airfoil and spring analogy is used to change the grid according to the change in shape of the airfoil. Aerodynamic coefficient required for response surface method are obtained by using Navier-Stokes solver with κ-ω shear stress transport turbulence model. For the baseline airfoils, OA 312, OA 309, and OA 407 airfoils select and optimize to improve aerodynamic performance.
사정환(J.H. Sa),전상언(S.E. Jeon),박수형(S.H. Park) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.2
Two-dimensional prediction capability of several analysis codes, such as XFOIL, MSES, and KFLOW, is compared and analyzed based on computational results of airfoil flows. To this end the transition transport equations are coupled with the Navier-Stokes equations for the prediction of the natural transition and the separation-induced transition. Experimental data of aerodynamic coefficients are used for comparison with numerical results for the transitional flows. Numerical predictions using the transition transport model show a good agreement with experimental data. Discrepancies have been found in the prediction of the pressure drag are mainly caused by the difference in the far-field circulation correction methods.
사정환(J.H. Sa),박수형(S.H. Park),김창주(C.J. Kim),강희정(H.J. Kang),김승범(S.B. Kim),김승호(S.H. Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
In this work, a comparative study is performed for simulation of rotor in hovering flight with a 3D compressible Navier-Stokes solver using overlapped grid systems. The shape of rotor blade consists of optimized rotor blade planforms. Optimized blade planforms are designed considering high performance on hovering and forward flight. To show the verification of optimized rotor blade planforms, blade loading(C<SUB>T</SUB>, FM, C<SUB>Q</SUB>) and the vortex behavior of optimized blade shape are compared with original blade shape.
HART Ⅱ 로터-동체 모델의 CFD/CSD 연계해석과 동체효과 분석
사정환(J.H. Sa),유영현(Y.H. You),박재상(J.S. Park),박수형(S.H. Park),정성남(S.N. Jung),유영훈(Y.H. Yu) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
A loosely coupling method is adopted to combine a computational fluid dynamics (CFD) solver and the comprehensive structural dynamics (CSD) code, CAMRAD Ⅱ, in a systematic manner to correlate the airloads, vortex trajectories, blade motions, and structural loads of the HART Ⅱ rotor in descending flight condition. A three-dimensional compressible Navier-Stokes solver, KFLOW, using chimera overlapped grids has been used to simulate unsteady flow phenomena over helicopter rotor blades. The number of grids used in the CFD computation is about 24 million for the isolated rotor and about 37.6 million for the rotor-fuselage configuration while keeping the background grid spacing identical as 10% blade chord length. The prediction of blade airloads is compared with the experimental data. The current method predicts reasonably well the BVI phenomena of blade airloads. The vortices generated from the fuselage have an influence on airloads in the 1st and 4th quadrants of rotor disk. It appeared that presence of the pylon cylinder resulted in complex turbulent flow field behind the hub center.
고받음각 델타익 유동의 와류 붕괴 모사를 위한 DES 해석
사정환(J.H. Sa),손미소(M. Son),박수형(S.H. Park),구기범(G. Gu),김민아(M. Kim),정경진(K.J. Jung) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
Detached Eddy Simulation(DES) is performed to understand vortex breakdown of a high-angle-of-attack Delta Wing flow. The fifth-order Upwind method is used to reduce turbulent dissipation. The computational results(DES) on ONERA Delta Wing model with a 70° sweep angle are compared with unsteady Reynolds-averaged Navier-Stokes(RANS) results and experimental data for validation with pressure distribution, surface pressure coefficient contour, and streamline distribution.