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김양준(Y.-J. Kim),정현주(H.-J. Jung),김태승(T.-S. Kim),손창호(C.-H. Son),조창열(C.-Y. Joh) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.2
A research to evaluate the efficiency of design optimization was carried out for aerodynamic design optimization problem in distributed computing environment. The aerodynamic analyses which take most oj computational work during design optimization were divided into several jobs and allocated to associated PC clients through network. This is not a parallel process based on domain decomposition in a single analysis rather than a simultaneous distributed-analyses using network-distributed computers. GBOM(gradient-based optimization method), SAO(Sequential Approximate Optimization) and RSM(Response Surface Method) were implemented to perform design optimization of transonic airfoils and evaluate their efficiencies. One dimensional minimization followed by direction search involved in the GBOM was found an obstacle against improving efficiency of the design process in the present distributed computing system. The SAO was found fairly suitable for the distributed computing environment even it has a handicap of local search. The RSM is apparently the most efficient algorithm in the present distributed computing environment, but additional trial and error works needed to enhance the reliability of the approximation model deteriorate its efficiency from the practical point of view.
RANS 방정식을 이용한 HAWT 로터 블레이드의 회전 유동장 해석
김태승(T.S. Kim),이철(C. Lee),손창호(C.H. Son),조창열(C.Y. Joh) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.2
The Reynolds-Averaged Navier-Stokes(RANS) analysis of the 3-D steady flow around the NREL Phase Ⅵ horizontal axis wind turbine(HAWT) rotor was performed. The CFD analysis results were compared with experimental data at several different wind speeds. The present CFD model shows good agreements with the experiments both at low wind speed which formed well-attache flow mostly on the upper surface of the blade, and at high wind speed which blade surface flow completely separated. However, some discrepancy occurs at the relatively high wind speeds where mixed attached and separated flow formed on the suction surface of the blade. It seems that the discrepancy is related to the onset of stall phenomena and consequently separation prediction capability of the current turbulence model. It is also found that strong span-wise flow occurs in stalled area due to the centrifugal force generated by rotation of the turbine rotor and it prevents abrupt reduction of normal force for higher wind speed than the designed value.
정지비행시 헬리콥터 로터 블레이드의 공력해석 및 최적화
제상언(S.E. Je),정현주(H.J. Jung),김도준(D.J. Kim),조창열(C.Y. Joh),명노신(R.S. Myong),박찬우(C.W. Park),조태환(T.H. Cho) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-
In this paper a method for the design optimization for helicopter rotor blade in hover is studied. Numerical analysis of aerodynamic characteristics of the flow around a rotor blade is analysed by usign panel method and CFD code based on Navier-Stokes equation. The result is validated by comparing with existing experimental result. Optimization methods RSM(Response Surface Method) and DOE(Design of Experiments) are applied in combination. The object functions are power, twist angle, taper ratio, and thrust. The optimized result showed a decrease of 17% of the power required.
정현주(H.-J. Jung),김태승(T.-S. Kim),손창호(C.-H. Son),조창열(C.-Y. Joh) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.3
Euler and Navier-Stokes flow analyses for helicopter rotor in hover were performed as low and high fidelity analysis models respectively for the future multidisciplinary design optimization(MDO). These design-oriented analyses possess several attributes such as variable complexity, sensitivity-computation capability and modularity which analysis models involved in MDO are recommended to provide with. To realize PC-based analyses for both fidelity models. reduction of flow domain was made by appling farfield boundary condition based on 3-dimensional point sink with simple momentum theory and also periodic boundary condition in the azimuthal direction. Correlations of thrust. torque and their sensitivities between low and high complexity models were tried to evaluate the applicability of these analysis models in MDO process. It was found that the low-fidelity Euler analysis model predicted inaccurate sensitivity derivatives at relatively high angle of attack.
Evaluation of Turbulence Models in a High Pressure Turbine Cascade Simulation
M.M. El-Gendi,K.-U. Lee(이경언),W.J. Chung(정의준),C.-Y. Joh(조창열),C.H. Son(손창호) 한국전산유체공학회 2012 한국전산유체공학회지 Vol.17 No.3
Steady flow simulations through a high pressure turbine guide vanes were carried out. The main objective of the present work is to study the performance of turbulence models on the steady flow prediction from aerodynamic and aerothermal points of view. Three turbulence models were compared, namely SST, k-ω and ω-Reynolds stress models. The laminar results were also compared. The comparison was done with emphasis on the isentropic Mach number and heat transfer coefficient along the blade, and total pressure loss in the wake region. The calculated isentropic Mach number showed reasonable agreement with experimental data along the blade surface for all three turbulent models. For the total pressure loss in the wake region, ω-Reynolds stress model showed the best agreement with the experimental data. However, unless using an appropriate transition model, the heat transfer coefficients of all three turbulent models showed poor agreement with experimental data.