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일반곡선 좌표계 사용시 대류항의 차분스킴에 의한 영향 평가
이연원 한국마린엔지니어링학회 1994 한국마린엔지니어링학회지 Vol.18 No.3
To develope the new simulator for the analysis of fluid flow information, the influence of various convective difference schemes were evaluated. General curvilinear coordinate system with nonorthogonal grids was adopted for the successful analysis of various complex geometries. Computation results show that if we can not obtain full grid numbers within available computational environment, we need to use higher order finite difference schemes to keep the prediction accuracy.
이연원 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.5
A diffuser an important equipment to change kinetic energy into pressure energy has been studied for a long time. Though experimental and theoretical researches habe been done the understanding of energy transfer and detailed mechanism of energy dissipation is unclear. As far as numerical prediction of diffuser flows are concerned various numerical studies have also been done. On the contrary many turbulence models have constraint to the applicability of diffuser-like flows with expansion and streamline curvature. In order to obtain the reliability of k-$\varepsilon$ turbulence model modified combination turbulence models composed of the anisotropic k-$\varepsilon$model modified combination turbulence models composed of the anisotropic k-$\varepsilon$ model with Hanjalic-Launder's preferential normal strain and Pope's vortex stretching mechanism are proposed. The results of the present proposed models prove the fact that the coefficient of pressure and the shear stress are well predicted at the diffuser flow.
이연원,김정환,김영덕,김태식 한국풍공학회 2005 한국풍공학회지 Vol.9 No.1
최근 관심이 급증하고 있는 풍력발전용 터빈의 효율적 설계기법의 확립 및 검증을 위해 상용 CFD 코드의 적용성 평가를 수행하였다. 상용 CFD 코드의 경우, 이미 다양한 분야에 걸쳐 그 적용 타당성을 검증 받은 바 있으나, 실제 풍력발전용 로터 블레이드 유동 및 성능해석에 대해서는 최근 들어 서서히 적용되기 시작했다. 상용 CFD 코드를 적용한 로터 후류 유동해석결과와 블레이드 표면 박리현상들은 NREL(National Renewable Energy Laboratory)의 결과와 TU-Delft의 BEM(Blade Element Method)에 의한 성능해석 결과와 상당히 유사한 결과를 나타낸다. The purpose of this 3-D numerical simulation is to evaluate the application of a commercial CFD code to predict 3-D flow and power characteristics of wind turbines. The experimental approach, which has been the main method of investigation, appears to be its limits, the cost is increasing with the size of the wind turbines, hence most observation are limited to the phenomena on rotor blades. Therefore, the use of Computational Fluid Dynamics (CFD) techniques and Navier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations in this paper. The 3-D flow separation and the wake distribution of 2 and 3 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and smoke-visualized experimental result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good consistent with smoke-visualized result. The calculated power of the 3 bladed rotor by CFD is compared with BEM results by TU-Delft. The CFD results, which are somewhat consistent with BEM results, have an error less than 10%.